* [PATCH v7 1/4] tracing: Reset last_boot_info if ring buffer is reset
From: Masami Hiramatsu (Google) @ 2026-02-09 9:25 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel
In-Reply-To: <177062912135.1230888.17419570791737357433.stgit@mhiramat.tok.corp.google.com>
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Commit 32dc0042528d ("tracing: Reset last-boot buffers when reading
out all cpu buffers") resets the last_boot_info when user read out
all data via trace_pipe* files. But it is not reset when user
resets the buffer from other files. (e.g. write `trace` file)
Reset it when the corresponding ring buffer is reset too.
Fixes: 32dc0042528d ("tracing: Reset last-boot buffers when reading out all cpu buffers")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v7:
- Remove unneeded update_last_data_if_empty() call from
tracing_snapshot_write() because snapshot is disabled on
persistent instances.
---
kernel/trace/trace.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 845b8a165daf..9e1cff78a1ca 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4127,6 +4127,8 @@ static int tracing_single_release_tr(struct inode *inode, struct file *file)
return single_release(inode, file);
}
+static bool update_last_data_if_empty(struct trace_array *tr);
+
static int tracing_open(struct inode *inode, struct file *file)
{
struct trace_array *tr = inode->i_private;
@@ -4151,6 +4153,8 @@ static int tracing_open(struct inode *inode, struct file *file)
tracing_reset_online_cpus(trace_buf);
else
tracing_reset_cpu(trace_buf, cpu);
+
+ update_last_data_if_empty(tr);
}
if (file->f_mode & FMODE_READ) {
@@ -5215,6 +5219,7 @@ tracing_set_trace_read(struct file *filp, char __user *ubuf,
int tracer_init(struct tracer *t, struct trace_array *tr)
{
tracing_reset_online_cpus(&tr->array_buffer);
+ update_last_data_if_empty(tr);
return t->init(tr);
}
@@ -7028,6 +7033,7 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr)
ring_buffer_set_clock(tr->snapshot_buffer.buffer, trace_clocks[i].func);
tracing_reset_online_cpus(&tr->snapshot_buffer);
#endif
+ update_last_data_if_empty(tr);
if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) {
struct trace_scratch *tscratch = tr->scratch;
^ permalink raw reply related
* [PATCH v7 0/4] tracing: Remove backup instance after read all
From: Masami Hiramatsu (Google) @ 2026-02-09 9:25 UTC (permalink / raw)
To: Steven Rostedt
Cc: Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel
Hi,
Here is the v7 of the series to improve backup instances of
the persistent ring buffer. The previous version is here:
https://lore.kernel.org/all/176991653525.4025429.12655335935351822711.stgit@mhiramat.tok.corp.google.com/
This version is rebased on the latest linux-trace/for-next,
remove update_last_data_if_empty() from snapshot file [1/4] and,
use -EACCES instead of -EPERM.
Series Description
------------------
Since backup instances are a kind of snapshot of the persistent
ring buffer, it should be readonly. And if it is readonly
there is no reason to keep it after reading all data via trace_pipe
because the data has been consumed. But user should be able to remove
the readonly instance by rmdir or truncating `trace` file.
Thus, [2/4] makes backup instances readonly (not able to write any
events, cleanup trace, change buffer size). Also, [3/4] removes the
backup instance after consuming all data via trace_pipe.
With this improvements, even if we makes a backup instance (using
the same amount of memory of the persistent ring buffer), it will
be removed after reading the data automatically.
---
Masami Hiramatsu (Google) (4):
tracing: Reset last_boot_info if ring buffer is reset
tracing: Make the backup instance non-reusable
tracing: Remove the backup instance automatically after read
tracing/Documentation: Add a section about backup instance
Documentation/trace/debugging.rst | 19 ++++
kernel/trace/trace.c | 161 ++++++++++++++++++++++++++++++-------
kernel/trace/trace.h | 13 +++
kernel/trace/trace_boot.c | 5 +
kernel/trace/trace_events.c | 76 ++++++++++-------
5 files changed, 208 insertions(+), 66 deletions(-)
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply
* [PATCH v2 4/4] tools/rtla: Remove unneeded nr_cpus from for_each_monitored_cpu
From: Costa Shulyupin @ 2026-02-09 9:24 UTC (permalink / raw)
To: Steven Rostedt, Tomas Glozar, Costa Shulyupin, Crystal Wood,
Wander Lairson Costa, Ivan Pravdin, John Kacur, Tiezhu Yang,
linux-trace-kernel, linux-kernel, bpf
In-Reply-To: <20260209092436.2899888-1-costa.shul@redhat.com>
nr_cpus does not change at runtime, so passing it through the macro
argument is unnecessary.
Remove the argument and use the global nr_cpus instead.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
---
tools/tracing/rtla/src/common.h | 2 +-
tools/tracing/rtla/src/osnoise_hist.c | 15 +++++++--------
tools/tracing/rtla/src/osnoise_top.c | 2 +-
tools/tracing/rtla/src/timerlat.c | 4 ++--
tools/tracing/rtla/src/timerlat_hist.c | 16 ++++++++--------
tools/tracing/rtla/src/timerlat_top.c | 2 +-
6 files changed, 20 insertions(+), 21 deletions(-)
diff --git a/tools/tracing/rtla/src/common.h b/tools/tracing/rtla/src/common.h
index 32f9c1351209..28d258d6d178 100644
--- a/tools/tracing/rtla/src/common.h
+++ b/tools/tracing/rtla/src/common.h
@@ -109,7 +109,7 @@ struct common_params {
extern int nr_cpus;
-#define for_each_monitored_cpu(cpu, nr_cpus, common) \
+#define for_each_monitored_cpu(cpu, common) \
for (cpu = 0; cpu < nr_cpus; cpu++) \
if (!(common)->cpus || CPU_ISSET(cpu, &(common)->monitored_cpus))
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 90291504a1aa..e8f07108d39a 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -244,7 +244,7 @@ static void osnoise_hist_header(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(s, "Index");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -273,8 +273,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "count:");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
-
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -285,7 +284,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "min: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -298,7 +297,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "avg: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -314,7 +313,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "max: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -349,7 +348,7 @@ osnoise_print_stats(struct osnoise_tool *tool)
trace_seq_printf(trace->seq, "%-6d",
bucket * data->bucket_size);
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -385,7 +384,7 @@ osnoise_print_stats(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "over: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 6fb3e72d74f2..ab5db35f21ae 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -236,7 +236,7 @@ osnoise_print_stats(struct osnoise_tool *top)
osnoise_top_header(top);
- for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(i, ¶ms->common) {
osnoise_top_print(top, i);
}
diff --git a/tools/tracing/rtla/src/timerlat.c b/tools/tracing/rtla/src/timerlat.c
index 69856f677fce..ec14abd45fff 100644
--- a/tools/tracing/rtla/src/timerlat.c
+++ b/tools/tracing/rtla/src/timerlat.c
@@ -115,7 +115,7 @@ int timerlat_enable(struct osnoise_tool *tool)
return -1;
}
- for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(i, ¶ms->common) {
if (save_cpu_idle_disable_state(i) < 0) {
err_msg("Could not save cpu idle state.\n");
return -1;
@@ -218,7 +218,7 @@ void timerlat_free(struct osnoise_tool *tool)
if (dma_latency_fd >= 0)
close(dma_latency_fd);
if (params->deepest_idle_state >= -1) {
- for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(i, ¶ms->common) {
restore_cpu_idle_disable_state(i);
}
}
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 4bf1489cad23..db66312ec966 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -298,7 +298,7 @@ static void timerlat_hist_header(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(s, "Index");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -350,7 +350,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "count:");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -372,7 +372,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "min: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -400,7 +400,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "avg: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -428,7 +428,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "max: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -473,7 +473,7 @@ timerlat_print_stats_all(struct timerlat_params *params,
sum.min_thread = ~0;
sum.min_user = ~0;
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -620,7 +620,7 @@ timerlat_print_stats(struct osnoise_tool *tool)
trace_seq_printf(trace->seq, "%-6d",
bucket * data->bucket_size);
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -658,7 +658,7 @@ timerlat_print_stats(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "over: ");
- for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 4eb820fe1f21..ed3d3d1c8956 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -446,7 +446,7 @@ timerlat_print_stats(struct osnoise_tool *top)
timerlat_top_header(params, top);
- for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(i, ¶ms->common) {
timerlat_top_print(top, i);
timerlat_top_update_sum(top, i, &summary);
}
--
2.52.0
^ permalink raw reply related
* [PATCH v2 3/4] tools/rtla: Remove unneeded nr_cpus members
From: Costa Shulyupin @ 2026-02-09 9:24 UTC (permalink / raw)
To: Steven Rostedt, Tomas Glozar, Costa Shulyupin, Crystal Wood,
Wander Lairson Costa, Ivan Pravdin, John Kacur, Tiezhu Yang,
linux-trace-kernel, linux-kernel, bpf
In-Reply-To: <20260209092436.2899888-1-costa.shul@redhat.com>
nr_cpus does not change at runtime, so keeping it in struct members is
unnecessary.
Use the global nr_cpus instead of struct members.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
---
tools/tracing/rtla/src/osnoise_hist.c | 18 ++++++------
tools/tracing/rtla/src/osnoise_top.c | 3 --
tools/tracing/rtla/src/timerlat_aa.c | 10 +++----
tools/tracing/rtla/src/timerlat_hist.c | 40 ++++++++++++--------------
tools/tracing/rtla/src/timerlat_top.c | 19 ++++++------
5 files changed, 39 insertions(+), 51 deletions(-)
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index d83ee047a5f5..90291504a1aa 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -29,7 +29,6 @@ struct osnoise_hist_data {
struct osnoise_hist_cpu *hist;
int entries;
int bucket_size;
- int nr_cpus;
};
/*
@@ -41,7 +40,7 @@ osnoise_free_histogram(struct osnoise_hist_data *data)
int cpu;
/* one histogram for IRQ and one for thread, per CPU */
- for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+ for (cpu = 0; cpu < nr_cpus; cpu++) {
if (data->hist[cpu].samples)
free(data->hist[cpu].samples);
}
@@ -73,7 +72,6 @@ static struct osnoise_hist_data
data->entries = entries;
data->bucket_size = bucket_size;
- data->nr_cpus = nr_cpus;
data->hist = calloc(1, sizeof(*data->hist) * nr_cpus);
if (!data->hist)
@@ -246,7 +244,7 @@ static void osnoise_hist_header(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(s, "Index");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -275,7 +273,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "count:");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -287,7 +285,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "min: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -300,7 +298,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "avg: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -316,7 +314,7 @@ osnoise_print_summary(struct osnoise_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "max: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -351,7 +349,7 @@ osnoise_print_stats(struct osnoise_tool *tool)
trace_seq_printf(trace->seq, "%-6d",
bucket * data->bucket_size);
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
@@ -387,7 +385,7 @@ osnoise_print_stats(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "over: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].count)
continue;
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 73b3ac0dd43b..6fb3e72d74f2 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -31,7 +31,6 @@ struct osnoise_top_cpu {
struct osnoise_top_data {
struct osnoise_top_cpu *cpu_data;
- int nr_cpus;
};
/*
@@ -59,8 +58,6 @@ static struct osnoise_top_data *osnoise_alloc_top(void)
if (!data)
return NULL;
- data->nr_cpus = nr_cpus;
-
/* one set of histograms per CPU */
data->cpu_data = calloc(1, sizeof(*data->cpu_data) * nr_cpus);
if (!data->cpu_data)
diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c
index 5766d58709eb..59b219a1503e 100644
--- a/tools/tracing/rtla/src/timerlat_aa.c
+++ b/tools/tracing/rtla/src/timerlat_aa.c
@@ -102,7 +102,6 @@ struct timerlat_aa_data {
* The analysis context and system wide view
*/
struct timerlat_aa_context {
- int nr_cpus;
int dump_tasks;
/* per CPU data */
@@ -738,7 +737,7 @@ void timerlat_auto_analysis(int irq_thresh, int thread_thresh)
irq_thresh = irq_thresh * 1000;
thread_thresh = thread_thresh * 1000;
- for (cpu = 0; cpu < taa_ctx->nr_cpus; cpu++) {
+ for (cpu = 0; cpu < nr_cpus; cpu++) {
taa_data = timerlat_aa_get_data(taa_ctx, cpu);
if (irq_thresh && taa_data->tlat_irq_latency >= irq_thresh) {
@@ -766,7 +765,7 @@ void timerlat_auto_analysis(int irq_thresh, int thread_thresh)
printf("\n");
printf("Printing CPU tasks:\n");
- for (cpu = 0; cpu < taa_ctx->nr_cpus; cpu++) {
+ for (cpu = 0; cpu < nr_cpus; cpu++) {
taa_data = timerlat_aa_get_data(taa_ctx, cpu);
tep = taa_ctx->tool->trace.tep;
@@ -792,7 +791,7 @@ static void timerlat_aa_destroy_seqs(struct timerlat_aa_context *taa_ctx)
if (!taa_ctx->taa_data)
return;
- for (i = 0; i < taa_ctx->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
taa_data = timerlat_aa_get_data(taa_ctx, i);
if (taa_data->prev_irqs_seq) {
@@ -842,7 +841,7 @@ static int timerlat_aa_init_seqs(struct timerlat_aa_context *taa_ctx)
struct timerlat_aa_data *taa_data;
int i;
- for (i = 0; i < taa_ctx->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
taa_data = timerlat_aa_get_data(taa_ctx, i);
@@ -1031,7 +1030,6 @@ int timerlat_aa_init(struct osnoise_tool *tool, int dump_tasks)
__timerlat_aa_ctx = taa_ctx;
- taa_ctx->nr_cpus = nr_cpus;
taa_ctx->tool = tool;
taa_ctx->dump_tasks = dump_tasks;
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index dee5fbf622c3..4bf1489cad23 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -44,7 +44,6 @@ struct timerlat_hist_data {
struct timerlat_hist_cpu *hist;
int entries;
int bucket_size;
- int nr_cpus;
};
/*
@@ -56,7 +55,7 @@ timerlat_free_histogram(struct timerlat_hist_data *data)
int cpu;
/* one histogram for IRQ and one for thread, per CPU */
- for (cpu = 0; cpu < data->nr_cpus; cpu++) {
+ for (cpu = 0; cpu < nr_cpus; cpu++) {
if (data->hist[cpu].irq)
free(data->hist[cpu].irq);
@@ -94,7 +93,6 @@ static struct timerlat_hist_data
data->entries = entries;
data->bucket_size = bucket_size;
- data->nr_cpus = nr_cpus;
/* one set of histograms per CPU */
data->hist = calloc(1, sizeof(*data->hist) * nr_cpus);
@@ -204,17 +202,17 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
{
struct timerlat_hist_data *data = tool->data;
int i, j, err;
- long long value_irq[data->nr_cpus],
- value_thread[data->nr_cpus],
- value_user[data->nr_cpus];
+ long long value_irq[nr_cpus],
+ value_thread[nr_cpus],
+ value_user[nr_cpus];
/* Pull histogram */
for (i = 0; i < data->entries; i++) {
err = timerlat_bpf_get_hist_value(i, value_irq, value_thread,
- value_user, data->nr_cpus);
+ value_user, nr_cpus);
if (err)
return err;
- for (j = 0; j < data->nr_cpus; j++) {
+ for (j = 0; j < nr_cpus; j++) {
data->hist[j].irq[i] = value_irq[j];
data->hist[j].thread[i] = value_thread[j];
data->hist[j].user[i] = value_user[j];
@@ -226,7 +224,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->hist[i].irq_count = value_irq[i];
data->hist[i].thread_count = value_thread[i];
data->hist[i].user_count = value_user[i];
@@ -236,7 +234,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->hist[i].min_irq = value_irq[i];
data->hist[i].min_thread = value_thread[i];
data->hist[i].min_user = value_user[i];
@@ -246,7 +244,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->hist[i].max_irq = value_irq[i];
data->hist[i].max_thread = value_thread[i];
data->hist[i].max_user = value_user[i];
@@ -256,7 +254,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->hist[i].sum_irq = value_irq[i];
data->hist[i].sum_thread = value_thread[i];
data->hist[i].sum_user = value_user[i];
@@ -266,7 +264,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->hist[i].irq[data->entries] = value_irq[i];
data->hist[i].thread[data->entries] = value_thread[i];
data->hist[i].user[data->entries] = value_user[i];
@@ -300,7 +298,7 @@ static void timerlat_hist_header(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(s, "Index");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -352,7 +350,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "count:");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -374,7 +372,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "min: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -402,7 +400,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "avg: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -430,7 +428,7 @@ timerlat_print_summary(struct timerlat_params *params,
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "max: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -475,7 +473,7 @@ timerlat_print_stats_all(struct timerlat_params *params,
sum.min_thread = ~0;
sum.min_user = ~0;
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -622,7 +620,7 @@ timerlat_print_stats(struct osnoise_tool *tool)
trace_seq_printf(trace->seq, "%-6d",
bucket * data->bucket_size);
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
@@ -660,7 +658,7 @@ timerlat_print_stats(struct osnoise_tool *tool)
if (!params->common.hist.no_index)
trace_seq_printf(trace->seq, "over: ");
- for_each_monitored_cpu(cpu, data->nr_cpus, ¶ms->common) {
+ for_each_monitored_cpu(cpu, nr_cpus, ¶ms->common) {
if (!data->hist[cpu].irq_count && !data->hist[cpu].thread_count)
continue;
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 25b4d81b4fe0..4eb820fe1f21 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -41,7 +41,6 @@ struct timerlat_top_cpu {
struct timerlat_top_data {
struct timerlat_top_cpu *cpu_data;
- int nr_cpus;
};
/*
@@ -71,8 +70,6 @@ static struct timerlat_top_data *timerlat_alloc_top(void)
if (!data)
return NULL;
- data->nr_cpus = nr_cpus;
-
/* one set of histograms per CPU */
data->cpu_data = calloc(1, sizeof(*data->cpu_data) * nr_cpus);
if (!data->cpu_data)
@@ -190,16 +187,16 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
{
struct timerlat_top_data *data = tool->data;
int i, err;
- long long value_irq[data->nr_cpus],
- value_thread[data->nr_cpus],
- value_user[data->nr_cpus];
+ long long value_irq[nr_cpus],
+ value_thread[nr_cpus],
+ value_user[nr_cpus];
/* Pull summary */
err = timerlat_bpf_get_summary_value(SUMMARY_CURRENT,
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->cpu_data[i].cur_irq = value_irq[i];
data->cpu_data[i].cur_thread = value_thread[i];
data->cpu_data[i].cur_user = value_user[i];
@@ -209,7 +206,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->cpu_data[i].irq_count = value_irq[i];
data->cpu_data[i].thread_count = value_thread[i];
data->cpu_data[i].user_count = value_user[i];
@@ -219,7 +216,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->cpu_data[i].min_irq = value_irq[i];
data->cpu_data[i].min_thread = value_thread[i];
data->cpu_data[i].min_user = value_user[i];
@@ -229,7 +226,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->cpu_data[i].max_irq = value_irq[i];
data->cpu_data[i].max_thread = value_thread[i];
data->cpu_data[i].max_user = value_user[i];
@@ -239,7 +236,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
value_irq, value_thread, value_user);
if (err)
return err;
- for (i = 0; i < data->nr_cpus; i++) {
+ for (i = 0; i < nr_cpus; i++) {
data->cpu_data[i].sum_irq = value_irq[i];
data->cpu_data[i].sum_thread = value_thread[i];
data->cpu_data[i].sum_user = value_user[i];
--
2.52.0
^ permalink raw reply related
* [PATCH v2 2/4] tools/rtla: Remove unneeded nr_cpus arguments
From: Costa Shulyupin @ 2026-02-09 9:24 UTC (permalink / raw)
To: Steven Rostedt, Tomas Glozar, Costa Shulyupin, Crystal Wood,
Wander Lairson Costa, Ivan Pravdin, John Kacur, Tiezhu Yang,
linux-trace-kernel, linux-kernel, bpf
In-Reply-To: <20260209092436.2899888-1-costa.shul@redhat.com>
nr_cpus does not change at runtime, so passing it through function
arguments is unnecessary.
Use the global nr_cpus instead of propagating it via parameters.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
---
tools/tracing/rtla/src/osnoise_hist.c | 4 ++--
tools/tracing/rtla/src/osnoise_top.c | 4 ++--
tools/tracing/rtla/src/timerlat_bpf.c | 5 ++---
tools/tracing/rtla/src/timerlat_bpf.h | 6 ++----
tools/tracing/rtla/src/timerlat_hist.c | 19 +++++++------------
tools/tracing/rtla/src/timerlat_top.c | 19 +++++++------------
tools/tracing/rtla/src/timerlat_u.c | 6 +++---
7 files changed, 25 insertions(+), 38 deletions(-)
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 03ebff34fff4..d83ee047a5f5 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -62,7 +62,7 @@ static void osnoise_free_hist_tool(struct osnoise_tool *tool)
* osnoise_alloc_histogram - alloc runtime data
*/
static struct osnoise_hist_data
-*osnoise_alloc_histogram(int nr_cpus, int entries, int bucket_size)
+*osnoise_alloc_histogram(int entries, int bucket_size)
{
struct osnoise_hist_data *data;
int cpu;
@@ -652,7 +652,7 @@ static struct osnoise_tool
if (!tool)
return NULL;
- tool->data = osnoise_alloc_histogram(nr_cpus, params->hist.entries,
+ tool->data = osnoise_alloc_histogram(params->hist.entries,
params->hist.bucket_size);
if (!tool->data)
goto out_err;
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index 7dcd2e318205..73b3ac0dd43b 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -51,7 +51,7 @@ static void osnoise_free_top_tool(struct osnoise_tool *tool)
/*
* osnoise_alloc_histogram - alloc runtime data
*/
-static struct osnoise_top_data *osnoise_alloc_top(int nr_cpus)
+static struct osnoise_top_data *osnoise_alloc_top(void)
{
struct osnoise_top_data *data;
@@ -496,7 +496,7 @@ struct osnoise_tool *osnoise_init_top(struct common_params *params)
if (!tool)
return NULL;
- tool->data = osnoise_alloc_top(nr_cpus);
+ tool->data = osnoise_alloc_top();
if (!tool->data) {
osnoise_destroy_tool(tool);
return NULL;
diff --git a/tools/tracing/rtla/src/timerlat_bpf.c b/tools/tracing/rtla/src/timerlat_bpf.c
index 05adf18303df..8d5c3a095e41 100644
--- a/tools/tracing/rtla/src/timerlat_bpf.c
+++ b/tools/tracing/rtla/src/timerlat_bpf.c
@@ -191,13 +191,12 @@ int timerlat_bpf_get_hist_value(int key,
int timerlat_bpf_get_summary_value(enum summary_field key,
long long *value_irq,
long long *value_thread,
- long long *value_user,
- int cpus)
+ long long *value_user)
{
return get_value(bpf->maps.summary_irq,
bpf->maps.summary_thread,
bpf->maps.summary_user,
- key, value_irq, value_thread, value_user, cpus);
+ key, value_irq, value_thread, value_user, nr_cpus);
}
/*
diff --git a/tools/tracing/rtla/src/timerlat_bpf.h b/tools/tracing/rtla/src/timerlat_bpf.h
index 169abeaf4363..f4a5476f2abb 100644
--- a/tools/tracing/rtla/src/timerlat_bpf.h
+++ b/tools/tracing/rtla/src/timerlat_bpf.h
@@ -28,8 +28,7 @@ int timerlat_bpf_get_hist_value(int key,
int timerlat_bpf_get_summary_value(enum summary_field key,
long long *value_irq,
long long *value_thread,
- long long *value_user,
- int cpus);
+ long long *value_user);
int timerlat_load_bpf_action_program(const char *program_path);
static inline int have_libbpf_support(void) { return 1; }
#else
@@ -53,8 +52,7 @@ static inline int timerlat_bpf_get_hist_value(int key,
static inline int timerlat_bpf_get_summary_value(enum summary_field key,
long long *value_irq,
long long *value_thread,
- long long *value_user,
- int cpus)
+ long long *value_user)
{
return -1;
}
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 841118ed84f2..dee5fbf622c3 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -83,7 +83,7 @@ static void timerlat_free_histogram_tool(struct osnoise_tool *tool)
* timerlat_alloc_histogram - alloc runtime data
*/
static struct timerlat_hist_data
-*timerlat_alloc_histogram(int nr_cpus, int entries, int bucket_size)
+*timerlat_alloc_histogram(int entries, int bucket_size)
{
struct timerlat_hist_data *data;
int cpu;
@@ -223,8 +223,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
/* Pull summary */
err = timerlat_bpf_get_summary_value(SUMMARY_COUNT,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -234,8 +233,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_MIN,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -245,8 +243,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_MAX,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -256,8 +253,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_SUM,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -267,8 +263,7 @@ static int timerlat_hist_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_OVERFLOW,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -1036,7 +1031,7 @@ static struct osnoise_tool
if (!tool)
return NULL;
- tool->data = timerlat_alloc_histogram(nr_cpus, params->hist.entries,
+ tool->data = timerlat_alloc_histogram(params->hist.entries,
params->hist.bucket_size);
if (!tool->data)
goto out_err;
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 3e395ce4fa9f..25b4d81b4fe0 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -62,7 +62,7 @@ static void timerlat_free_top_tool(struct osnoise_tool *tool)
/*
* timerlat_alloc_histogram - alloc runtime data
*/
-static struct timerlat_top_data *timerlat_alloc_top(int nr_cpus)
+static struct timerlat_top_data *timerlat_alloc_top(void)
{
struct timerlat_top_data *data;
int cpu;
@@ -196,8 +196,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
/* Pull summary */
err = timerlat_bpf_get_summary_value(SUMMARY_CURRENT,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -207,8 +206,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_COUNT,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -218,8 +216,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_MIN,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -229,8 +226,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_MAX,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -240,8 +236,7 @@ static int timerlat_top_bpf_pull_data(struct osnoise_tool *tool)
}
err = timerlat_bpf_get_summary_value(SUMMARY_SUM,
- value_irq, value_thread, value_user,
- data->nr_cpus);
+ value_irq, value_thread, value_user);
if (err)
return err;
for (i = 0; i < data->nr_cpus; i++) {
@@ -782,7 +777,7 @@ static struct osnoise_tool
if (!top)
return NULL;
- top->data = timerlat_alloc_top(nr_cpus);
+ top->data = timerlat_alloc_top();
if (!top->data)
goto out_err;
diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
index a569fe7f93aa..03b4e68e8b1e 100644
--- a/tools/tracing/rtla/src/timerlat_u.c
+++ b/tools/tracing/rtla/src/timerlat_u.c
@@ -99,7 +99,7 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
*
* Return the number of processes that received the kill.
*/
-static int timerlat_u_send_kill(pid_t *procs, int nr_cpus)
+static int timerlat_u_send_kill(pid_t *procs)
{
int killed = 0;
int i, retval;
@@ -169,7 +169,7 @@ void *timerlat_u_dispatcher(void *data)
/* parent */
if (pid == -1) {
- timerlat_u_send_kill(procs, nr_cpus);
+ timerlat_u_send_kill(procs);
debug_msg("Failed to create child processes");
pthread_exit(&retval);
}
@@ -196,7 +196,7 @@ void *timerlat_u_dispatcher(void *data)
sleep(1);
}
- timerlat_u_send_kill(procs, nr_cpus);
+ timerlat_u_send_kill(procs);
while (procs_count) {
pid = waitpid(-1, &wstatus, 0);
--
2.52.0
^ permalink raw reply related
* [PATCH v2 1/4] tools/rtla: Consolidate nr_cpus usage across all tools
From: Costa Shulyupin @ 2026-02-09 9:24 UTC (permalink / raw)
To: Steven Rostedt, Tomas Glozar, Costa Shulyupin, Crystal Wood,
Wander Lairson Costa, Ivan Pravdin, John Kacur, Tiezhu Yang,
linux-trace-kernel, linux-kernel, bpf
In-Reply-To: <20260209092436.2899888-1-costa.shul@redhat.com>
sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects
cpu_possible_mask, which is fixed at boot time, so querying it
repeatedly is unnecessary.
Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single
global nr_cpus variable initialized once at startup.
`#pragma once` in timerlat_u.h is needed for pre-C23 compilers to avoid
redefinition errors.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
---
tools/tracing/rtla/src/common.c | 7 +++++--
tools/tracing/rtla/src/common.h | 2 ++
tools/tracing/rtla/src/osnoise_hist.c | 3 ---
tools/tracing/rtla/src/osnoise_top.c | 7 -------
tools/tracing/rtla/src/timerlat.c | 5 +----
tools/tracing/rtla/src/timerlat_aa.c | 1 -
tools/tracing/rtla/src/timerlat_hist.c | 3 ---
tools/tracing/rtla/src/timerlat_top.c | 7 -------
tools/tracing/rtla/src/timerlat_u.c | 3 +--
tools/tracing/rtla/src/timerlat_u.h | 1 +
tools/tracing/rtla/src/utils.c | 10 +---------
11 files changed, 11 insertions(+), 38 deletions(-)
diff --git a/tools/tracing/rtla/src/common.c b/tools/tracing/rtla/src/common.c
index ceff76a62a30..e4cf30a65e82 100644
--- a/tools/tracing/rtla/src/common.c
+++ b/tools/tracing/rtla/src/common.c
@@ -5,12 +5,14 @@
#include <signal.h>
#include <stdlib.h>
#include <string.h>
-#include <unistd.h>
#include <getopt.h>
+#include <sys/sysinfo.h>
+
#include "common.h"
struct trace_instance *trace_inst;
volatile int stop_tracing;
+int nr_cpus;
static void stop_trace(int sig)
{
@@ -135,7 +137,7 @@ common_apply_config(struct osnoise_tool *tool, struct common_params *params)
}
if (!params->cpus) {
- for (i = 0; i < sysconf(_SC_NPROCESSORS_CONF); i++)
+ for (i = 0; i < nr_cpus; i++)
CPU_SET(i, ¶ms->monitored_cpus);
}
@@ -183,6 +185,7 @@ int run_tool(struct tool_ops *ops, int argc, char *argv[])
bool stopped;
int retval;
+ nr_cpus = get_nprocs_conf();
params = ops->parse_args(argc, argv);
if (!params)
exit(1);
diff --git a/tools/tracing/rtla/src/common.h b/tools/tracing/rtla/src/common.h
index 7602c5593ef5..32f9c1351209 100644
--- a/tools/tracing/rtla/src/common.h
+++ b/tools/tracing/rtla/src/common.h
@@ -107,6 +107,8 @@ struct common_params {
struct timerlat_u_params user;
};
+extern int nr_cpus;
+
#define for_each_monitored_cpu(cpu, nr_cpus, common) \
for (cpu = 0; cpu < nr_cpus; cpu++) \
if (!(common)->cpus || CPU_ISSET(cpu, &(common)->monitored_cpus))
diff --git a/tools/tracing/rtla/src/osnoise_hist.c b/tools/tracing/rtla/src/osnoise_hist.c
index 9d70ea34807f..03ebff34fff4 100644
--- a/tools/tracing/rtla/src/osnoise_hist.c
+++ b/tools/tracing/rtla/src/osnoise_hist.c
@@ -647,9 +647,6 @@ static struct osnoise_tool
*osnoise_init_hist(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("osnoise_hist");
if (!tool)
diff --git a/tools/tracing/rtla/src/osnoise_top.c b/tools/tracing/rtla/src/osnoise_top.c
index d54d47947fb4..7dcd2e318205 100644
--- a/tools/tracing/rtla/src/osnoise_top.c
+++ b/tools/tracing/rtla/src/osnoise_top.c
@@ -232,12 +232,8 @@ osnoise_print_stats(struct osnoise_tool *top)
{
struct osnoise_params *params = to_osnoise_params(top->params);
struct trace_instance *trace = &top->trace;
- static int nr_cpus = -1;
int i;
- if (nr_cpus == -1)
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
if (!params->common.quiet)
clear_terminal(trace->seq);
@@ -495,9 +491,6 @@ osnoise_top_apply_config(struct osnoise_tool *tool)
struct osnoise_tool *osnoise_init_top(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("osnoise_top");
if (!tool)
diff --git a/tools/tracing/rtla/src/timerlat.c b/tools/tracing/rtla/src/timerlat.c
index 8f8811f7a13b..69856f677fce 100644
--- a/tools/tracing/rtla/src/timerlat.c
+++ b/tools/tracing/rtla/src/timerlat.c
@@ -99,7 +99,7 @@ timerlat_apply_config(struct osnoise_tool *tool, struct timerlat_params *params)
int timerlat_enable(struct osnoise_tool *tool)
{
struct timerlat_params *params = to_timerlat_params(tool->params);
- int retval, nr_cpus, i;
+ int retval, i;
if (params->dma_latency >= 0) {
dma_latency_fd = set_cpu_dma_latency(params->dma_latency);
@@ -115,8 +115,6 @@ int timerlat_enable(struct osnoise_tool *tool)
return -1;
}
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for_each_monitored_cpu(i, nr_cpus, ¶ms->common) {
if (save_cpu_idle_disable_state(i) < 0) {
err_msg("Could not save cpu idle state.\n");
@@ -214,7 +212,6 @@ void timerlat_analyze(struct osnoise_tool *tool, bool stopped)
void timerlat_free(struct osnoise_tool *tool)
{
struct timerlat_params *params = to_timerlat_params(tool->params);
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
int i;
timerlat_aa_destroy();
diff --git a/tools/tracing/rtla/src/timerlat_aa.c b/tools/tracing/rtla/src/timerlat_aa.c
index 31e66ea2b144..5766d58709eb 100644
--- a/tools/tracing/rtla/src/timerlat_aa.c
+++ b/tools/tracing/rtla/src/timerlat_aa.c
@@ -1022,7 +1022,6 @@ void timerlat_aa_destroy(void)
*/
int timerlat_aa_init(struct osnoise_tool *tool, int dump_tasks)
{
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
struct timerlat_aa_context *taa_ctx;
int retval;
diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 4e8c38a61197..841118ed84f2 100644
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -1031,9 +1031,6 @@ static struct osnoise_tool
*timerlat_init_hist(struct common_params *params)
{
struct osnoise_tool *tool;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
tool = osnoise_init_tool("timerlat_hist");
if (!tool)
diff --git a/tools/tracing/rtla/src/timerlat_top.c b/tools/tracing/rtla/src/timerlat_top.c
index 284b74773c2b..3e395ce4fa9f 100644
--- a/tools/tracing/rtla/src/timerlat_top.c
+++ b/tools/tracing/rtla/src/timerlat_top.c
@@ -442,15 +442,11 @@ timerlat_print_stats(struct osnoise_tool *top)
struct timerlat_params *params = to_timerlat_params(top->params);
struct trace_instance *trace = &top->trace;
struct timerlat_top_cpu summary;
- static int nr_cpus = -1;
int i;
if (params->common.aa_only)
return;
- if (nr_cpus == -1)
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
if (!params->common.quiet)
clear_terminal(trace->seq);
@@ -781,9 +777,6 @@ static struct osnoise_tool
*timerlat_init_top(struct common_params *params)
{
struct osnoise_tool *top;
- int nr_cpus;
-
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
top = osnoise_init_tool("timerlat_top");
if (!top)
diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
index ce68e39d25fd..a569fe7f93aa 100644
--- a/tools/tracing/rtla/src/timerlat_u.c
+++ b/tools/tracing/rtla/src/timerlat_u.c
@@ -16,7 +16,7 @@
#include <sys/wait.h>
#include <sys/prctl.h>
-#include "utils.h"
+#include "common.h"
#include "timerlat_u.h"
/*
@@ -131,7 +131,6 @@ static int timerlat_u_send_kill(pid_t *procs, int nr_cpus)
*/
void *timerlat_u_dispatcher(void *data)
{
- int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
struct timerlat_u_params *params = data;
char proc_name[128];
int procs_count = 0;
diff --git a/tools/tracing/rtla/src/timerlat_u.h b/tools/tracing/rtla/src/timerlat_u.h
index 661511908957..a692331bd1c7 100644
--- a/tools/tracing/rtla/src/timerlat_u.h
+++ b/tools/tracing/rtla/src/timerlat_u.h
@@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
+#pragma once
/*
* Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org>
*/
diff --git a/tools/tracing/rtla/src/utils.c b/tools/tracing/rtla/src/utils.c
index 0da3b2470c31..8cd1b374b035 100644
--- a/tools/tracing/rtla/src/utils.c
+++ b/tools/tracing/rtla/src/utils.c
@@ -19,7 +19,7 @@
#include <stdio.h>
#include <limits.h>
-#include "utils.h"
+#include "common.h"
#define MAX_MSG_LENGTH 1024
int config_debug;
@@ -119,14 +119,11 @@ int parse_cpu_set(char *cpu_list, cpu_set_t *set)
{
const char *p;
int end_cpu;
- int nr_cpus;
int cpu;
int i;
CPU_ZERO(set);
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for (p = cpu_list; *p; ) {
cpu = atoi(p);
if (cpu < 0 || (!cpu && *p != '0') || cpu >= nr_cpus)
@@ -559,7 +556,6 @@ int save_cpu_idle_disable_state(unsigned int cpu)
unsigned int nr_states;
unsigned int state;
int disabled;
- int nr_cpus;
nr_states = cpuidle_state_count(cpu);
@@ -567,7 +563,6 @@ int save_cpu_idle_disable_state(unsigned int cpu)
return 0;
if (saved_cpu_idle_disable_state == NULL) {
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
saved_cpu_idle_disable_state = calloc(nr_cpus, sizeof(unsigned int *));
if (!saved_cpu_idle_disable_state)
return -1;
@@ -644,13 +639,10 @@ int restore_cpu_idle_disable_state(unsigned int cpu)
void free_cpu_idle_disable_states(void)
{
int cpu;
- int nr_cpus;
if (!saved_cpu_idle_disable_state)
return;
- nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
-
for (cpu = 0; cpu < nr_cpus; cpu++) {
free(saved_cpu_idle_disable_state[cpu]);
saved_cpu_idle_disable_state[cpu] = NULL;
--
2.52.0
^ permalink raw reply related
* [PATCH v2 0/4] tools/rtla: Consolidate nr_cpus usage
From: Costa Shulyupin @ 2026-02-09 9:24 UTC (permalink / raw)
To: Steven Rostedt, Tomas Glozar, Costa Shulyupin, Crystal Wood,
Wander Lairson Costa, Ivan Pravdin, John Kacur, Tiezhu Yang,
linux-trace-kernel, linux-kernel, bpf
sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects
cpu_possible_mask, which is fixed at boot time, so querying it
repeatedly is unnecessary.
Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single
global nr_cpus variable initialized once at startup.
v2:
- Add `#pragma once` in timerlat_u.h to avoid redefinition errors with
pre-C23 compilers.
Costa Shulyupin (4):
tools/rtla: Consolidate nr_cpus usage across all tools
tools/rtla: Remove unneeded nr_cpus arguments
tools/rtla: Remove unneeded nr_cpus members
tools/rtla: Remove unneeded nr_cpus from for_each_monitored_cpu
tools/tracing/rtla/src/common.c | 7 ++-
tools/tracing/rtla/src/common.h | 4 +-
tools/tracing/rtla/src/osnoise_hist.c | 26 +++++------
tools/tracing/rtla/src/osnoise_top.c | 16 ++-----
tools/tracing/rtla/src/timerlat.c | 9 ++--
tools/tracing/rtla/src/timerlat_aa.c | 11 ++---
tools/tracing/rtla/src/timerlat_bpf.c | 5 +--
tools/tracing/rtla/src/timerlat_bpf.h | 6 +--
tools/tracing/rtla/src/timerlat_hist.c | 62 +++++++++++---------------
tools/tracing/rtla/src/timerlat_top.c | 47 +++++++------------
tools/tracing/rtla/src/timerlat_u.c | 9 ++--
tools/tracing/rtla/src/timerlat_u.h | 1 +
tools/tracing/rtla/src/utils.c | 10 +----
13 files changed, 80 insertions(+), 133 deletions(-)
--
2.52.0
^ permalink raw reply
* Re: [PATCH v6 2/4] tracing: Make the backup instance non-reusable
From: Masami Hiramatsu @ 2026-02-09 9:08 UTC (permalink / raw)
To: Steven Rostedt; +Cc: Mathieu Desnoyers, linux-kernel, linux-trace-kernel
In-Reply-To: <20260204211721.74e501f0@robin>
On Wed, 4 Feb 2026 21:17:21 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> On Sun, 1 Feb 2026 12:29:15 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
> > Since there is no reason to reuse the backup instance, make it
> > readonly (but erasable).
> > Note that only backup instances are readonly, because
> > other trace instances will be empty unless it is writable.
> > Only backup instances have copy entries from the original.
> >
> > With this change, most of the trace control files are removed
> > from the backup instance, including eventfs enable/filter etc.
> >
> > # find /sys/kernel/tracing/instances/backup/events/ | wc -l
> > 4093
> > # find /sys/kernel/tracing/instances/boot_map/events/ | wc -l
> > 9573
> >
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> > ---
> > Changes in v6:
> > - Remove tracing_on file from readonly instances.
> > - Remove unused writable_mode from tracing_init_tracefs_percpu().
> > - Cleanup init_tracer_tracefs() and create_event_toplevel_files().
> > - Remove TRACE_MODE_WRITE_MASK.
> > - Add TRACE_ARRAY_FL_RDONLY.
> > Changes in v5:
> > - Rebased on the latest for-next (and hide show_event_filters/triggers
> > if the instance is readonly.
> > Changes in v4:
> > - Make trace data erasable. (not reusable)
> > Changes in v3:
> > - Resuse the beginning part of event_entries for readonly files.
> > - Remove readonly file_operations and checking readonly flag in
> > each write operation.
> > Changes in v2:
> > - Use readonly file_operations to prohibit writing instead of
> > checking flags in write() callbacks.
> > - Remove writable files from eventfs.
> > ---
> > kernel/trace/trace.c | 94 +++++++++++++++++++++++++++++--------------
> > kernel/trace/trace.h | 7 +++
> > kernel/trace/trace_boot.c | 5 +-
> > kernel/trace/trace_events.c | 76 ++++++++++++++++++++---------------
> > 4 files changed, 117 insertions(+), 65 deletions(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 5c3e4a554143..b0efcf1e0809 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -5052,6 +5052,11 @@ static ssize_t
> > tracing_write_stub(struct file *filp, const char __user *ubuf,
> > size_t count, loff_t *ppos)
> > {
> > + struct trace_array *tr = file_inode(filp)->i_private;
> > +
> > + if (trace_array_is_readonly(tr))
> > + return -EPERM;
> > +
> > return count;
> > }
> >
> > @@ -5152,6 +5157,9 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
> > cpumask_var_t tracing_cpumask_new;
> > int err;
> >
> > + if (trace_array_is_readonly(tr))
> > + return -EPERM;
> > +
>
> Shouldn't these checks be done in the open function? Doing it now is
> too late, as -EPERM on a write is confusing when the open for write
> succeeds.
I've made a small program and straced. Surprisingly, for the super user,
open(2) does not return error on opening a readonly file with O_RDWR.
With normal user, it returns -EACCES
-----
$ strace ./write-test hoge
execve("./write-test", ["./write-test", "hoge"], 0x7ffc30b99928 /* 73 vars */) = 0
...
openat(AT_FDCWD, "hoge", O_RDWR) = -1 EACCES (Permission denied)
exit_group(-1) = ?
+++ exited with 255 +++
-----
But for the superuser case:
-----
$ sudo strace ./write-test hoge
execve("./write-test", ["./write-test", "hoge"], 0x7ffcffa80488 /* 32 vars */) = 0
...
openat(AT_FDCWD, "hoge", O_RDWR) = 3
write(3, "test\0", 5) = 5
fstat(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(0x88, 0x2), ...}) = 0
write(1, "write return 5\n", 15write return 5
) = 15
exit_group(0) = ?
+++ exited with 0 +++
So I think we can postpone it until actual action for the superuser case.
(Anyway, I will make it return -EACCES)
Thank you,
>
> -- Steve
>
> > if (count == 0 || count > KMALLOC_MAX_SIZE)
> > return -EINVAL;
> >
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply
* [PATCH] tracing: Pretty-print enum parameters in function arguments
From: Donglin Peng @ 2026-02-09 7:19 UTC (permalink / raw)
To: rostedt; +Cc: mhiramat, linux-trace-kernel, linux-kernel, Donglin Peng
From: Donglin Peng <pengdonglin@xiaomi.com>
Currently, print_function_args() prints enum parameter values
in decimal format, reducing trace log readability.
Use BTF information to resolve enum parameters and print their
symbolic names (where available). This improves readability by
showing meaningful identifiers instead of raw numbers.
Before:
mod_memcg_lruvec_state(lruvec=0xffff..., idx=5, val=320)
After:
mod_memcg_lruvec_state(lruvec=0xffff..., idx=5 [NR_SLAB_RECLAIMABLE_B], val=320)
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Donglin Peng <pengdonglin@xiaomi.com>
---
v2:
- Iterate btf_enum members directly with a for loop,
replacing the for_each_enum macro helper.
---
kernel/trace/trace_output.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index cc2d3306bb60..548e3cd06b04 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -695,12 +695,13 @@ void print_function_args(struct trace_seq *s, unsigned long *args,
{
const struct btf_param *param;
const struct btf_type *t;
+ const struct btf_enum *enums;
const char *param_name;
char name[KSYM_NAME_LEN];
unsigned long arg;
struct btf *btf;
s32 tid, nr = 0;
- int a, p, x;
+ int a, p, x, i;
u16 encode;
trace_seq_printf(s, "(");
@@ -754,6 +755,15 @@ void print_function_args(struct trace_seq *s, unsigned long *args,
break;
case BTF_KIND_ENUM:
trace_seq_printf(s, "%ld", arg);
+ enums = btf_enum(t);
+ for (i = 0; i < btf_vlen(t); i++) {
+ if (arg == enums[i].val) {
+ trace_seq_printf(s, " [%s]",
+ btf_name_by_offset(btf,
+ enums[i].name_off));
+ break;
+ }
+ }
break;
default:
/* This does not handle complex arguments */
--
2.34.1
^ permalink raw reply related
* Re: [PATCH] tracing: Have all triggers expect a file parameter
From: Tom Zanussi @ 2026-02-08 22:49 UTC (permalink / raw)
To: Steven Rostedt, LKML, Linux Trace Kernel
Cc: Masami Hiramatsu, Mathieu Desnoyers
In-Reply-To: <20260206101351.609d8906@gandalf.local.home>
Hi Steve,
On Fri, 2026-02-06 at 10:13 -0500, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> When the triggers were first created, they may not have had a file
> parameter passed to them and things needed to be done generically.
>
> But today, all triggers have a file parameter passed to them. Remove the
> generic code and add a "if (WARN_ON_ONCE(!file))" to each trigger.
>
Makes sense.
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> kernel/trace/trace_events_trigger.c | 62 +++++++++++------------------
> 1 file changed, 24 insertions(+), 38 deletions(-)
>
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index 06b75bcfc7b8..7fa26327c9c7 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -1347,18 +1347,13 @@ traceon_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (tracer_tracing_is_on(file->tr))
> - return;
> -
> - tracer_tracing_on(file->tr);
> + if (WARN_ON_ONCE(!file))
> return;
> - }
>
> - if (tracing_is_on())
> + if (tracer_tracing_is_on(file->tr))
> return;
>
> - tracing_on();
> + tracer_tracing_on(file->tr);
> }
>
> static bool
> @@ -1368,13 +1363,11 @@ traceon_count_func(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (tracer_tracing_is_on(file->tr))
> - return false;
> - } else {
> - if (tracing_is_on())
> - return false;
> - }
> + if (WARN_ON_ONCE(!file))
> + return false;
> +
> + if (tracer_tracing_is_on(file->tr))
> + return false;
>
> if (!data->count)
> return false;
> @@ -1392,18 +1385,13 @@ traceoff_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (!tracer_tracing_is_on(file->tr))
> - return;
> -
> - tracer_tracing_off(file->tr);
> + if (WARN_ON_ONCE(!file))
> return;
> - }
>
> - if (!tracing_is_on())
> + if (!tracer_tracing_is_on(file->tr))
> return;
>
> - tracing_off();
> + tracer_tracing_off(file->tr);
> }
>
> static bool
> @@ -1413,13 +1401,11 @@ traceoff_count_func(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (!tracer_tracing_is_on(file->tr))
> - return false;
> - } else {
> - if (!tracing_is_on())
> - return false;
> - }
> + if (WARN_ON_ONCE(!file))
> + return false;
> +
> + if (!tracer_tracing_is_on(file->tr))
> + return false;
>
> if (!data->count)
> return false;
> @@ -1481,10 +1467,10 @@ snapshot_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file)
> - tracing_snapshot_instance(file->tr);
> - else
> - tracing_snapshot();
> + if (WARN_ON_ONCE(!file))
> + return;
> +
> + tracing_snapshot_instance(file->tr);
> }
>
> static int
> @@ -1570,10 +1556,10 @@ stacktrace_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file)
> - __trace_stack(file->tr, tracing_gen_ctx_dec(), STACK_SKIP);
> - else
> - trace_dump_stack(STACK_SKIP);
> + if (WARN_ON_ONCE(!file))
> + return;
> +
> + __trace_stack(file->tr, tracing_gen_ctx_dec(), STACK_SKIP);
> }
>
> static int
^ permalink raw reply
* Re: [RFC bpf-next 00/12] bpf: tracing_multi link
From: Jiri Olsa @ 2026-02-08 20:54 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Jiri Olsa, Alexei Starovoitov, Alexei Starovoitov,
Daniel Borkmann, Andrii Nakryiko, bpf, linux-trace-kernel,
Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
Menglong Dong, Steven Rostedt
In-Reply-To: <CAEf4BzbUX8xEp1x66ugtj1C6sxWPJ+_9EpyVmy3TVOMiKrFcWA@mail.gmail.com>
On Fri, Feb 06, 2026 at 09:03:29AM -0800, Andrii Nakryiko wrote:
> On Fri, Feb 6, 2026 at 12:18 AM Jiri Olsa <olsajiri@gmail.com> wrote:
> >
> > On Thu, Feb 05, 2026 at 07:55:19AM -0800, Alexei Starovoitov wrote:
> > > On Thu, Feb 5, 2026 at 12:55 AM Jiri Olsa <olsajiri@gmail.com> wrote:
> > > >
> > > > On Wed, Feb 04, 2026 at 08:06:50AM -0800, Alexei Starovoitov wrote:
> > > > > On Wed, Feb 4, 2026 at 4:36 AM Jiri Olsa <olsajiri@gmail.com> wrote:
> > > > > >
> > > > > > On Tue, Feb 03, 2026 at 03:17:05PM -0800, Alexei Starovoitov wrote:
> > > > > > > On Tue, Feb 3, 2026 at 1:38 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > > > > > > >
> > > > > > > > hi,
> > > > > > > > as an option to Meglong's change [1] I'm sending proposal for tracing_multi
> > > > > > > > link that does not add static trampoline but attaches program to all needed
> > > > > > > > trampolines.
> > > > > > > >
> > > > > > > > This approach keeps the same performance but has some drawbacks:
> > > > > > > >
> > > > > > > > - when attaching 20k functions we allocate and attach 20k trampolines
> > > > > > > > - during attachment we hold each trampoline mutex, so for above
> > > > > > > > 20k functions we will hold 20k mutexes during the attachment,
> > > > > > > > should be very prone to deadlock, but haven't hit it yet
> > > > > > >
> > > > > > > If you check that it's sorted and always take them in the same order
> > > > > > > then there will be no deadlock.
> > > > > > > Or just grab one global mutex first and then grab trampolines mutexes
> > > > > > > next in any order. The global one will serialize this attach operation.
> > > > > > >
> > > > > > > > It looks the trampoline allocations/generation might not be big a problem
> > > > > > > > and I'll try to find a solution for holding that many mutexes. If there's
> > > > > > > > no better solution I think having one read/write mutex for tracing multi
> > > > > > > > link attach/detach should work.
> > > > > > >
> > > > > > > If you mean to have one global mutex as I proposed above then I don't see
> > > > > > > a downside. It only serializes multiple libbpf calls.
> > > > > >
> > > > > > we also need to serialize it with standard single trampoline attach,
> > > > > > because the direct ftrace update is now done under trampoline->mutex:
> > > > > >
> > > > > > bpf_trampoline_link_prog(tr)
> > > > > > {
> > > > > > mutex_lock(&tr->mutex);
> > > > > > ...
> > > > > > update_ftrace_direct_*
> > > > > > ...
> > > > > > mutex_unlock(&tr->mutex);
> > > > > > }
> > > > > >
> > > > > > for tracing_multi we would link the program first (with tr->mutex)
> > > > > > and do the bulk ftrace update later (without tr->mutex)
> > > > > >
> > > > > > {
> > > > > > for each involved trampoline:
> > > > > > bpf_trampoline_link_prog
> > > > > >
> > > > > > --> and here we could race with some other thread doing single
> > > > > > trampoline attach
> > > > > >
> > > > > > update_ftrace_direct_*
> > > > > > }
> > > > > >
> > > > > > note the current version locks all tr->mutex instances all the way
> > > > > > through the update_ftrace_direct_* update
> > > > > >
> > > > > > I think we could use global rwsem and take read lock on single
> > > > > > trampoline attach path and write lock on tracing_multi attach,
> > > > > >
> > > > > > I thought we could take direct_mutex early, but that would mean
> > > > > > different order with trampoline mutex than we already have in
> > > > > > single attach path
> > > > >
> > > > > I feel we're talking past each other.
> > > > > I meant:
> > > > >
> > > > > For multi:
> > > > > 1. take some global mutex
> > > > > 2. take N tramp mutexes in any order
> > > > >
> > > > > For single:
> > > > > 1. take that 1 specific tramp mutex.
> > > >
> > > > ah ok, I understand, it's to prevent the lockup but keep holding all
> > > > the trampolines locks.. the rwsem I mentioned was for the 'fix', where
> > > > we do not take all the trampolines locks
> > >
> > > I don't understand how rwsem would help.
> > > All the operations on trampoline are protected by mutex.
> > > Switching to rw makes sense only if we can designate certain
> > > operations as "read" and others as "write" and number of "reads"
> > > dominate. This won't be the case with multi-fentry.
> > > And we still need to take all of them as "write" to update trampoline.
> >
> > this applies to scenario where we do not hold all the trampoline locks,
> > in such case we could have race between single and multi attachment,
> > while single/single attachment race stays safe
> >
> > as a fix the single attach would take read lock and multi attach would
> > take write lock, so single/single race is allowed and single/multi is
> > not ... showed in the patch below
> >
> > but it might be too much.. in a sense that there's already many locks
> > involved in trampoline attach/detach, and simple global lock in multi
> > or just sorting the ids would be enough
> >
>
> I'll just throw this idea here, but we don't have to do it right away.
> What if instead of having a per-trampoline lock, we just have a common
> relatively small pool of locks that all trampolines share based on
> some hash (i.e., we deterministically map trampoline to one of the
> locks). Then multi-attach can just go and grab all of them in
> predefined order, while singular trampoline attaches will just get
> their own one. We won't need to sort anything, we reduce the amount of
> different locks. I don't think lock contention (due to lock sharing
> for some trampolines) is a real issue to be worried about either.
nice idea, I'll check on that
thanks,
jirka
^ permalink raw reply
* [PATCH v3 2/3] tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
From: Steven Rostedt @ 2026-02-08 18:38 UTC (permalink / raw)
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton
In-Reply-To: <20260208183832.118080581@kernel.org>
From: Steven Rostedt <rostedt@goodmis.org>
Instead of having #ifdef CONFIG_TRACER_MAX_TRACE around every access to
the struct tracer's use_max_tr field, add a helper function for that
access and if CONFIG_TRACER_MAX_TRACE is not configured it just returns
false.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v2: https://patch.msgid.link/20260208040221.900653834@kernel.org
- Fix tracing_set_tracer() when CONFIG_TRACER_SNAPSHOT is not enabled.
Seems that some fields that are only available with that config were
still exposed, and the local variable used was still hidden.
(kernel test robot)
kernel/trace/trace.c | 51 ++++++++++++++------------------------------
kernel/trace/trace.h | 12 +++++++++++
2 files changed, 28 insertions(+), 35 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 98524d0656bf..405212166677 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -810,7 +810,6 @@ EXPORT_SYMBOL_GPL(tracing_on);
static void tracing_snapshot_instance_cond(struct trace_array *tr,
void *cond_data)
{
- struct tracer *tracer = tr->current_trace;
unsigned long flags;
if (in_nmi()) {
@@ -827,7 +826,7 @@ static void tracing_snapshot_instance_cond(struct trace_array *tr,
}
/* Note, snapshot can not be used when the tracer uses it */
- if (tracer->use_max_tr) {
+ if (tracer_uses_snapshot(tr->current_trace)) {
trace_array_puts(tr, "*** LATENCY TRACER ACTIVE ***\n");
trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
return;
@@ -1076,7 +1075,7 @@ int tracing_snapshot_cond_enable(struct trace_array *tr, void *cond_data,
guard(mutex)(&trace_types_lock);
- if (tr->current_trace->use_max_tr)
+ if (tracer_uses_snapshot(tr->current_trace))
return -EBUSY;
/*
@@ -1787,7 +1786,7 @@ static int run_tracer_selftest(struct tracer *type)
tr->current_trace_flags = type->flags ? : type->default_flags;
#ifdef CONFIG_TRACER_MAX_TRACE
- if (type->use_max_tr) {
+ if (tracer_uses_snapshot(type)) {
/* If we expanded the buffers, make sure the max is expanded too */
if (tr->ring_buffer_expanded)
ring_buffer_resize(tr->snapshot_buffer.buffer, trace_buf_size,
@@ -1812,7 +1811,7 @@ static int run_tracer_selftest(struct tracer *type)
tracing_reset_online_cpus(&tr->array_buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
- if (type->use_max_tr) {
+ if (tracer_uses_snapshot(type)) {
tr->allocated_snapshot = false;
/* Shrink the max buffer again */
@@ -3240,10 +3239,8 @@ static void *s_start(struct seq_file *m, loff_t *pos)
}
mutex_unlock(&trace_types_lock);
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (iter->snapshot && iter->trace->use_max_tr)
+ if (iter->snapshot && tracer_uses_snapshot(iter->trace))
return ERR_PTR(-EBUSY);
-#endif
if (*pos != iter->pos) {
iter->ent = NULL;
@@ -3282,10 +3279,8 @@ static void s_stop(struct seq_file *m, void *p)
{
struct trace_iterator *iter = m->private;
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (iter->snapshot && iter->trace->use_max_tr)
+ if (iter->snapshot && tracer_uses_snapshot(iter->trace))
return;
-#endif
trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
@@ -4177,11 +4172,9 @@ static int tracing_open(struct inode *inode, struct file *file)
static bool
trace_ok_for_array(struct tracer *t, struct trace_array *tr)
{
-#ifdef CONFIG_TRACER_SNAPSHOT
/* arrays with mapped buffer range do not have snapshots */
- if (tr->range_addr_start && t->use_max_tr)
+ if (tr->range_addr_start && tracer_uses_snapshot(t))
return false;
-#endif
return (tr->flags & TRACE_ARRAY_FL_GLOBAL) || t->allow_instances;
}
@@ -5550,9 +5543,7 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
{
struct tracer *trace = NULL;
struct tracers *t;
-#ifdef CONFIG_TRACER_MAX_TRACE
bool had_max_tr;
-#endif
int ret;
guard(mutex)(&trace_types_lock);
@@ -5580,7 +5571,7 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
return 0;
#ifdef CONFIG_TRACER_SNAPSHOT
- if (trace->use_max_tr) {
+ if (tracer_uses_snapshot(trace)) {
local_irq_disable();
arch_spin_lock(&tr->max_lock);
ret = tr->cond_snapshot ? -EBUSY : 0;
@@ -5612,14 +5603,13 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
if (tr->current_trace->reset)
tr->current_trace->reset(tr);
-#ifdef CONFIG_TRACER_MAX_TRACE
- had_max_tr = tr->current_trace->use_max_tr;
+ had_max_tr = tracer_uses_snapshot(tr->current_trace);
/* Current trace needs to be nop_trace before synchronize_rcu */
tr->current_trace = &nop_trace;
tr->current_trace_flags = nop_trace.flags;
- if (had_max_tr && !trace->use_max_tr) {
+ if (had_max_tr && !tracer_uses_snapshot(trace)) {
/*
* We need to make sure that the update_max_tr sees that
* current_trace changed to nop_trace to keep it from
@@ -5632,24 +5622,19 @@ int tracing_set_tracer(struct trace_array *tr, const char *buf)
tracing_disarm_snapshot(tr);
}
- if (!had_max_tr && trace->use_max_tr) {
+ if (!had_max_tr && tracer_uses_snapshot(trace)) {
ret = tracing_arm_snapshot_locked(tr);
if (ret)
return ret;
}
-#else
- tr->current_trace = &nop_trace;
-#endif
tr->current_trace_flags = t->flags ? : t->tracer->flags;
if (trace->init) {
ret = tracer_init(trace, tr);
if (ret) {
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (trace->use_max_tr)
+ if (tracer_uses_snapshot(trace))
tracing_disarm_snapshot(tr);
-#endif
tr->current_trace_flags = nop_trace.flags;
return ret;
}
@@ -7207,7 +7192,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
guard(mutex)(&trace_types_lock);
- if (tr->current_trace->use_max_tr)
+ if (tracer_uses_snapshot(tr->current_trace))
return -EBUSY;
local_irq_disable();
@@ -7306,7 +7291,7 @@ static int snapshot_raw_open(struct inode *inode, struct file *filp)
info = filp->private_data;
- if (info->iter.trace->use_max_tr) {
+ if (tracer_uses_snapshot(info->iter.trace)) {
tracing_buffers_release(inode, filp);
return -EBUSY;
}
@@ -7862,10 +7847,8 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
if (!count)
return 0;
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (iter->snapshot && iter->tr->current_trace->use_max_tr)
+ if (iter->snapshot && tracer_uses_snapshot(iter->tr->current_trace))
return -EBUSY;
-#endif
page_size = ring_buffer_subbuf_size_get(iter->array_buffer->buffer);
@@ -8049,10 +8032,8 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
int entries, i;
ssize_t ret = 0;
-#ifdef CONFIG_TRACER_MAX_TRACE
- if (iter->snapshot && iter->tr->current_trace->use_max_tr)
+ if (iter->snapshot && tracer_uses_snapshot(iter->tr->current_trace))
return -EBUSY;
-#endif
page_size = ring_buffer_subbuf_size_get(iter->array_buffer->buffer);
if (*ppos & (page_size - 1))
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b50383aa8e50..ebb47abc0ee7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -817,6 +817,18 @@ static inline void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
}
#endif /* CONFIG_STACKTRACE */
+#ifdef CONFIG_TRACER_MAX_TRACE
+static inline bool tracer_uses_snapshot(struct tracer *tracer)
+{
+ return tracer->use_max_tr;
+}
+#else
+static inline bool tracer_uses_snapshot(struct tracer *tracer)
+{
+ return false;
+}
+#endif
+
void trace_last_func_repeats(struct trace_array *tr,
struct trace_func_repeats *last_info,
unsigned int trace_ctx);
--
2.51.0
^ permalink raw reply related
* [PATCH v3 3/3] tracing: Better separate SNAPSHOT and MAX_TRACE options
From: Steven Rostedt @ 2026-02-08 18:38 UTC (permalink / raw)
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton
In-Reply-To: <20260208183832.118080581@kernel.org>
From: Steven Rostedt <rostedt@goodmis.org>
The latency tracers (scheduler, irqsoff, etc) were created when tracing
was first added. These tracers required a "snapshot" buffer that was the
same size as the ring buffer being written to. When a new max latency was
hit, the main ring buffer would swap with the snapshot buffer so that the
trace leading up to the latency would be saved in the snapshot buffer (The
snapshot buffer is never written to directly and the data within it can be
viewed without fear of being overwritten).
Later, a new feature was added to allow snapshots to be taken by user
space or even event triggers. This created a "snapshot" file that allowed
users to trigger a snapshot from user space to save the current trace.
The config for this new feature (CONFIG_TRACER_SNAPSHOT) would select the
latency tracer config (CONFIG_TRACER_MAX_LATENCY) as it would need all the
functionality from it as it already existed. But this was incorrect. As
the snapshot feature is really what the latency tracers need and not the
other way around.
Have CONFIG_TRACER_MAX_TRACE select CONFIG_TRACER_SNAPSHOT where the
tracers that needs the max latency buffer selects the TRACE_MAX_TRACE
which will then select TRACER_SNAPSHOT.
Also, go through trace.c and trace.h and make the code that only needs the
TRACER_MAX_TRACE protected by that and the code that always requires the
snapshot to be protected by TRACER_SNAPSHOT.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v2: https://patch.msgid.link/20260208040222.068849312@kernel.org
- Fix trace_create_maxlat_file() declaration when CONFIG_TRACER_SNAPSHOT
is not defined.
kernel/trace/Kconfig | 8 ++---
kernel/trace/trace.c | 73 +++++++++++++++++++++++---------------------
kernel/trace/trace.h | 19 +++++++-----
3 files changed, 53 insertions(+), 47 deletions(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index bfa2ec46e075..bedb2f982823 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -133,6 +133,7 @@ config BUILDTIME_MCOUNT_SORT
config TRACER_MAX_TRACE
bool
+ select TRACER_SNAPSHOT
config TRACE_CLOCK
bool
@@ -422,7 +423,6 @@ config IRQSOFF_TRACER
select GENERIC_TRACER
select TRACER_MAX_TRACE
select RING_BUFFER_ALLOW_SWAP
- select TRACER_SNAPSHOT
select TRACER_SNAPSHOT_PER_CPU_SWAP
help
This option measures the time spent in irqs-off critical
@@ -445,7 +445,6 @@ config PREEMPT_TRACER
select GENERIC_TRACER
select TRACER_MAX_TRACE
select RING_BUFFER_ALLOW_SWAP
- select TRACER_SNAPSHOT
select TRACER_SNAPSHOT_PER_CPU_SWAP
select TRACE_PREEMPT_TOGGLE
help
@@ -467,7 +466,6 @@ config SCHED_TRACER
select GENERIC_TRACER
select CONTEXT_SWITCH_TRACER
select TRACER_MAX_TRACE
- select TRACER_SNAPSHOT
help
This tracer tracks the latency of the highest priority task
to be scheduled in, starting from the point it has woken up.
@@ -617,7 +615,6 @@ config TRACE_SYSCALL_BUF_SIZE_DEFAULT
config TRACER_SNAPSHOT
bool "Create a snapshot trace buffer"
- select TRACER_MAX_TRACE
help
Allow tracing users to take snapshot of the current buffer using the
ftrace interface, e.g.:
@@ -625,6 +622,9 @@ config TRACER_SNAPSHOT
echo 1 > /sys/kernel/tracing/snapshot
cat snapshot
+ Note, the latency tracers select this option. To disable it,
+ all the latency tracers need to be disabled.
+
config TRACER_SNAPSHOT_PER_CPU_SWAP
bool "Allow snapshot to swap per CPU"
depends on TRACER_SNAPSHOT
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 405212166677..845b8a165daf 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -825,15 +825,15 @@ static void tracing_snapshot_instance_cond(struct trace_array *tr,
return;
}
- /* Note, snapshot can not be used when the tracer uses it */
- if (tracer_uses_snapshot(tr->current_trace)) {
- trace_array_puts(tr, "*** LATENCY TRACER ACTIVE ***\n");
+ if (tr->mapped) {
+ trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n");
trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
return;
}
- if (tr->mapped) {
- trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n");
+ /* Note, snapshot can not be used when the tracer uses it */
+ if (tracer_uses_snapshot(tr->current_trace)) {
+ trace_array_puts(tr, "*** LATENCY TRACER ACTIVE ***\n");
trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
return;
}
@@ -1555,8 +1555,8 @@ static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
struct array_buffer *trace_buf = &tr->array_buffer;
- struct array_buffer *max_buf = &tr->snapshot_buffer;
struct trace_array_cpu *data = per_cpu_ptr(trace_buf->data, cpu);
+ struct array_buffer *max_buf = &tr->snapshot_buffer;
struct trace_array_cpu *max_data = per_cpu_ptr(max_buf->data, cpu);
max_buf->cpu = cpu;
@@ -1585,7 +1585,14 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
tracing_record_cmdline(tsk);
latency_fsnotify(tr);
}
+#else
+static inline void trace_create_maxlat_file(struct trace_array *tr,
+ struct dentry *d_tracer) { }
+static inline void __update_max_tr(struct trace_array *tr,
+ struct task_struct *tsk, int cpu) { }
+#endif /* CONFIG_TRACER_MAX_TRACE */
+#ifdef CONFIG_TRACER_SNAPSHOT
/**
* update_max_tr - snapshot all trace buffers from global_trace to max_tr
* @tr: tracer
@@ -1619,12 +1626,11 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
else
ring_buffer_record_off(tr->snapshot_buffer.buffer);
-#ifdef CONFIG_TRACER_SNAPSHOT
if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data)) {
arch_spin_unlock(&tr->max_lock);
return;
}
-#endif
+
swap(tr->array_buffer.buffer, tr->snapshot_buffer.buffer);
__update_max_tr(tr, tsk, cpu);
@@ -1679,10 +1685,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
__update_max_tr(tr, tsk, cpu);
arch_spin_unlock(&tr->max_lock);
}
-#else /* !CONFIG_TRACER_MAX_TRACE */
-static inline void trace_create_maxlat_file(struct trace_array *tr,
- struct dentry *d_tracer) { }
-#endif /* CONFIG_TRACER_MAX_TRACE */
+#endif /* CONFIG_TRACER_SNAPSHOT */
struct pipe_wait {
struct trace_iterator *iter;
@@ -1715,7 +1718,7 @@ static int wait_on_pipe(struct trace_iterator *iter, int full)
ret = ring_buffer_wait(iter->array_buffer->buffer, iter->cpu_file, full,
wait_pipe_cond, &pwait);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
/*
* Make sure this is still the snapshot buffer, as if a snapshot were
* to happen, this would now be the main buffer.
@@ -2058,7 +2061,7 @@ void tracing_reset_all_online_cpus_unlocked(void)
continue;
tr->clear_trace = false;
tracing_reset_online_cpus(&tr->array_buffer);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
tracing_reset_online_cpus(&tr->snapshot_buffer);
#endif
}
@@ -2098,7 +2101,7 @@ static void tracing_start_tr(struct trace_array *tr)
if (buffer)
ring_buffer_record_enable(buffer);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
buffer = tr->snapshot_buffer.buffer;
if (buffer)
ring_buffer_record_enable(buffer);
@@ -2134,7 +2137,7 @@ static void tracing_stop_tr(struct trace_array *tr)
if (buffer)
ring_buffer_record_disable(buffer);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
buffer = tr->snapshot_buffer.buffer;
if (buffer)
ring_buffer_record_disable(buffer);
@@ -3757,7 +3760,7 @@ static void test_ftrace_alive(struct seq_file *m)
"# MAY BE MISSING FUNCTION EVENTS\n");
}
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
static void show_snapshot_main_help(struct seq_file *m)
{
seq_puts(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n"
@@ -3935,7 +3938,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
iter->tr = tr;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
/* Currently only the top directory has a snapshot */
if (tr->current_trace->print_max || snapshot)
iter->array_buffer = &tr->snapshot_buffer;
@@ -4351,14 +4354,14 @@ int tracing_set_cpumask(struct trace_array *tr,
if (cpumask_test_cpu(cpu, tr->tracing_cpumask) &&
!cpumask_test_cpu(cpu, tracing_cpumask_new)) {
ring_buffer_record_disable_cpu(tr->array_buffer.buffer, cpu);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
ring_buffer_record_disable_cpu(tr->snapshot_buffer.buffer, cpu);
#endif
}
if (!cpumask_test_cpu(cpu, tr->tracing_cpumask) &&
cpumask_test_cpu(cpu, tracing_cpumask_new)) {
ring_buffer_record_enable_cpu(tr->array_buffer.buffer, cpu);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
ring_buffer_record_enable_cpu(tr->snapshot_buffer.buffer, cpu);
#endif
}
@@ -4568,7 +4571,7 @@ int set_tracer_flag(struct trace_array *tr, u64 mask, int enabled)
case TRACE_ITER(OVERWRITE):
ring_buffer_change_overwrite(tr->array_buffer.buffer, enabled);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
ring_buffer_change_overwrite(tr->snapshot_buffer.buffer, enabled);
#endif
break;
@@ -5232,7 +5235,7 @@ static void update_buffer_entries(struct array_buffer *buf, int cpu)
}
}
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
/* resize @tr's buffer to the size of @size_tr's entries */
static int resize_buffer_duplicate_size(struct array_buffer *trace_buf,
struct array_buffer *size_buf, int cpu_id)
@@ -5258,7 +5261,7 @@ static int resize_buffer_duplicate_size(struct array_buffer *trace_buf,
return ret;
}
-#endif /* CONFIG_TRACER_MAX_TRACE */
+#endif /* CONFIG_TRACER_SNAPSHOT */
static int __tracing_resize_ring_buffer(struct trace_array *tr,
unsigned long size, int cpu)
@@ -5283,7 +5286,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
if (ret < 0)
goto out_start;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
if (!tr->allocated_snapshot)
goto out;
@@ -5315,7 +5318,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
update_buffer_entries(&tr->snapshot_buffer, cpu);
out:
-#endif /* CONFIG_TRACER_MAX_TRACE */
+#endif /* CONFIG_TRACER_SNAPSHOT */
update_buffer_entries(&tr->array_buffer, cpu);
out_start:
@@ -7020,7 +7023,7 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr)
*/
tracing_reset_online_cpus(&tr->array_buffer);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
if (tr->snapshot_buffer.buffer)
ring_buffer_set_clock(tr->snapshot_buffer.buffer, trace_clocks[i].func);
tracing_reset_online_cpus(&tr->snapshot_buffer);
@@ -8167,7 +8170,7 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned
return 0;
}
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
static int get_snapshot_map(struct trace_array *tr)
{
int err = 0;
@@ -9171,7 +9174,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf,
if (ret)
goto out;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
if (!tr->allocated_snapshot)
goto out_max;
@@ -9392,7 +9395,7 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
if (ret)
return ret;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
/* Fix mapped buffer trace arrays do not have snapshot buffers */
if (tr->range_addr_start)
return 0;
@@ -9419,7 +9422,7 @@ static void free_trace_buffers(struct trace_array *tr)
free_trace_buffer(&tr->array_buffer);
kfree(tr->module_delta);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
free_trace_buffer(&tr->snapshot_buffer);
#endif
}
@@ -9561,7 +9564,7 @@ trace_array_create_systems(const char *name, const char *systems,
tr->syscall_buf_sz = global_trace.syscall_buf_sz;
tr->max_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
spin_lock_init(&tr->snapshot_trigger_lock);
#endif
tr->current_trace = &nop_trace;
@@ -10515,7 +10518,7 @@ ssize_t trace_parse_run_command(struct file *file, const char __user *buffer,
return done;
}
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
__init static bool tr_needs_alloc_snapshot(const char *name)
{
char *test;
@@ -10705,7 +10708,7 @@ __init static void enable_instances(void)
}
} else {
/* Only non mapped buffers have snapshot buffers */
- if (IS_ENABLED(CONFIG_TRACER_MAX_TRACE))
+ if (IS_ENABLED(CONFIG_TRACER_SNAPSHOT))
do_allocate_snapshot(name);
}
@@ -10832,7 +10835,7 @@ __init static int tracer_alloc_buffers(void)
global_trace.current_trace_flags = nop_trace.flags;
global_trace.max_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
spin_lock_init(&global_trace.snapshot_trigger_lock);
#endif
ftrace_init_global_array_ops(&global_trace);
@@ -10900,7 +10903,7 @@ struct trace_array *trace_get_global_array(void)
void __init ftrace_boot_snapshot(void)
{
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
struct trace_array *tr;
if (!snapshot_at_boot)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index ebb47abc0ee7..649fdd20fc91 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -329,7 +329,7 @@ struct trace_array {
struct list_head list;
char *name;
struct array_buffer array_buffer;
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
/*
* The snapshot_buffer is used to snapshot the trace when a maximum
* latency is reached, or when the user initiates a snapshot.
@@ -346,13 +346,16 @@ struct trace_array {
bool allocated_snapshot;
spinlock_t snapshot_trigger_lock;
unsigned int snapshot;
+#ifdef CONFIG_TRACER_MAX_TRACE
unsigned long max_latency;
#ifdef CONFIG_FSNOTIFY
struct dentry *d_max_latency;
struct work_struct fsnotify_work;
struct irq_work fsnotify_irqwork;
-#endif
-#endif
+#endif /* CONFIG_FSNOTIFY */
+#endif /* CONFIG_TRACER_MAX_TRACE */
+#endif /* CONFIG_TRACER_SNAPSHOT */
+
/* The below is for memory mapped ring buffer */
unsigned int mapped;
unsigned long range_addr_start;
@@ -378,7 +381,7 @@ struct trace_array {
*
* It is also used in other places outside the update_max_tr
* so it needs to be defined outside of the
- * CONFIG_TRACER_MAX_TRACE.
+ * CONFIG_TRACER_SNAPSHOT.
*/
arch_spinlock_t max_lock;
#ifdef CONFIG_FTRACE_SYSCALLS
@@ -791,22 +794,22 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
struct trace_pid_list **new_pid_list,
const char __user *ubuf, size_t cnt);
-#ifdef CONFIG_TRACER_MAX_TRACE
+#ifdef CONFIG_TRACER_SNAPSHOT
void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
void *cond_data);
void update_max_tr_single(struct trace_array *tr,
struct task_struct *tsk, int cpu);
-#ifdef CONFIG_FSNOTIFY
-#define LATENCY_FS_NOTIFY
+#if defined(CONFIG_TRACER_MAX_TRACE) && defined(CONFIG_FSNOTIFY)
+# define LATENCY_FS_NOTIFY
#endif
-#endif /* CONFIG_TRACER_MAX_TRACE */
#ifdef LATENCY_FS_NOTIFY
void latency_fsnotify(struct trace_array *tr);
#else
static inline void latency_fsnotify(struct trace_array *tr) { }
#endif
+#endif /* CONFIG_TRACER_SNAPSHOT */
#ifdef CONFIG_STACKTRACE
void __trace_stack(struct trace_array *tr, unsigned int trace_ctx, int skip);
--
2.51.0
^ permalink raw reply related
* [PATCH v3 1/3] tracing: Rename trace_array field max_buffer to snapshot_buffer
From: Steven Rostedt @ 2026-02-08 18:38 UTC (permalink / raw)
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton
In-Reply-To: <20260208183832.118080581@kernel.org>
From: Steven Rostedt <rostedt@goodmis.org>
When tracing was first added, there were latency tracers that would take a
snapshot of the current trace when a new max latency was hit. This
snapshot buffer was called "max_buffer". Since then, a snapshot feature
was added that allowed user space or event triggers to trigger a snapshot
of the current buffer using the same max_buffer of the trace_array.
As this snapshot buffer now has a more generic use case, calling it
"max_buffer" is confusing. Rename it to snapshot_buffer.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 72 +++++++++++++++++------------------
kernel/trace/trace.h | 13 ++++---
kernel/trace/trace_selftest.c | 10 ++---
3 files changed, 48 insertions(+), 47 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 551a452befa0..98524d0656bf 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -934,12 +934,12 @@ int tracing_alloc_snapshot_instance(struct trace_array *tr)
/* Make the snapshot buffer have the same order as main buffer */
order = ring_buffer_subbuf_order_get(tr->array_buffer.buffer);
- ret = ring_buffer_subbuf_order_set(tr->max_buffer.buffer, order);
+ ret = ring_buffer_subbuf_order_set(tr->snapshot_buffer.buffer, order);
if (ret < 0)
return ret;
/* allocate spare buffer */
- ret = resize_buffer_duplicate_size(&tr->max_buffer,
+ ret = resize_buffer_duplicate_size(&tr->snapshot_buffer,
&tr->array_buffer, RING_BUFFER_ALL_CPUS);
if (ret < 0)
return ret;
@@ -957,10 +957,10 @@ static void free_snapshot(struct trace_array *tr)
* The max_tr ring buffer has some state (e.g. ring->clock) and
* we want preserve it.
*/
- ring_buffer_subbuf_order_set(tr->max_buffer.buffer, 0);
- ring_buffer_resize(tr->max_buffer.buffer, 1, RING_BUFFER_ALL_CPUS);
- set_buffer_entries(&tr->max_buffer, 1);
- tracing_reset_online_cpus(&tr->max_buffer);
+ ring_buffer_subbuf_order_set(tr->snapshot_buffer.buffer, 0);
+ ring_buffer_resize(tr->snapshot_buffer.buffer, 1, RING_BUFFER_ALL_CPUS);
+ set_buffer_entries(&tr->snapshot_buffer, 1);
+ tracing_reset_online_cpus(&tr->snapshot_buffer);
tr->allocated_snapshot = false;
}
@@ -1556,7 +1556,7 @@ static void
__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
{
struct array_buffer *trace_buf = &tr->array_buffer;
- struct array_buffer *max_buf = &tr->max_buffer;
+ struct array_buffer *max_buf = &tr->snapshot_buffer;
struct trace_array_cpu *data = per_cpu_ptr(trace_buf->data, cpu);
struct trace_array_cpu *max_data = per_cpu_ptr(max_buf->data, cpu);
@@ -1616,9 +1616,9 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
/* Inherit the recordable setting from array_buffer */
if (ring_buffer_record_is_set_on(tr->array_buffer.buffer))
- ring_buffer_record_on(tr->max_buffer.buffer);
+ ring_buffer_record_on(tr->snapshot_buffer.buffer);
else
- ring_buffer_record_off(tr->max_buffer.buffer);
+ ring_buffer_record_off(tr->snapshot_buffer.buffer);
#ifdef CONFIG_TRACER_SNAPSHOT
if (tr->cond_snapshot && !tr->cond_snapshot->update(tr, cond_data)) {
@@ -1626,7 +1626,7 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu,
return;
}
#endif
- swap(tr->array_buffer.buffer, tr->max_buffer.buffer);
+ swap(tr->array_buffer.buffer, tr->snapshot_buffer.buffer);
__update_max_tr(tr, tsk, cpu);
@@ -1661,7 +1661,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
arch_spin_lock(&tr->max_lock);
- ret = ring_buffer_swap_cpu(tr->max_buffer.buffer, tr->array_buffer.buffer, cpu);
+ ret = ring_buffer_swap_cpu(tr->snapshot_buffer.buffer, tr->array_buffer.buffer, cpu);
if (ret == -EBUSY) {
/*
@@ -1671,7 +1671,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
* and flag that it failed.
* Another reason is resize is in progress.
*/
- trace_array_printk_buf(tr->max_buffer.buffer, _THIS_IP_,
+ trace_array_printk_buf(tr->snapshot_buffer.buffer, _THIS_IP_,
"Failed to swap buffers due to commit or resize in progress\n");
}
@@ -1722,7 +1722,7 @@ static int wait_on_pipe(struct trace_iterator *iter, int full)
* to happen, this would now be the main buffer.
*/
if (iter->snapshot)
- iter->array_buffer = &iter->tr->max_buffer;
+ iter->array_buffer = &iter->tr->snapshot_buffer;
#endif
return ret;
}
@@ -1790,7 +1790,7 @@ static int run_tracer_selftest(struct tracer *type)
if (type->use_max_tr) {
/* If we expanded the buffers, make sure the max is expanded too */
if (tr->ring_buffer_expanded)
- ring_buffer_resize(tr->max_buffer.buffer, trace_buf_size,
+ ring_buffer_resize(tr->snapshot_buffer.buffer, trace_buf_size,
RING_BUFFER_ALL_CPUS);
tr->allocated_snapshot = true;
}
@@ -1817,7 +1817,7 @@ static int run_tracer_selftest(struct tracer *type)
/* Shrink the max buffer again */
if (tr->ring_buffer_expanded)
- ring_buffer_resize(tr->max_buffer.buffer, 1,
+ ring_buffer_resize(tr->snapshot_buffer.buffer, 1,
RING_BUFFER_ALL_CPUS);
}
#endif
@@ -2060,7 +2060,7 @@ void tracing_reset_all_online_cpus_unlocked(void)
tr->clear_trace = false;
tracing_reset_online_cpus(&tr->array_buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
- tracing_reset_online_cpus(&tr->max_buffer);
+ tracing_reset_online_cpus(&tr->snapshot_buffer);
#endif
}
}
@@ -2100,7 +2100,7 @@ static void tracing_start_tr(struct trace_array *tr)
ring_buffer_record_enable(buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
- buffer = tr->max_buffer.buffer;
+ buffer = tr->snapshot_buffer.buffer;
if (buffer)
ring_buffer_record_enable(buffer);
#endif
@@ -2136,7 +2136,7 @@ static void tracing_stop_tr(struct trace_array *tr)
ring_buffer_record_disable(buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
- buffer = tr->max_buffer.buffer;
+ buffer = tr->snapshot_buffer.buffer;
if (buffer)
ring_buffer_record_disable(buffer);
#endif
@@ -3943,7 +3943,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
#ifdef CONFIG_TRACER_MAX_TRACE
/* Currently only the top directory has a snapshot */
if (tr->current_trace->print_max || snapshot)
- iter->array_buffer = &tr->max_buffer;
+ iter->array_buffer = &tr->snapshot_buffer;
else
#endif
iter->array_buffer = &tr->array_buffer;
@@ -4146,7 +4146,7 @@ static int tracing_open(struct inode *inode, struct file *file)
#ifdef CONFIG_TRACER_MAX_TRACE
if (tr->current_trace->print_max)
- trace_buf = &tr->max_buffer;
+ trace_buf = &tr->snapshot_buffer;
#endif
if (cpu == RING_BUFFER_ALL_CPUS)
@@ -4359,14 +4359,14 @@ int tracing_set_cpumask(struct trace_array *tr,
!cpumask_test_cpu(cpu, tracing_cpumask_new)) {
ring_buffer_record_disable_cpu(tr->array_buffer.buffer, cpu);
#ifdef CONFIG_TRACER_MAX_TRACE
- ring_buffer_record_disable_cpu(tr->max_buffer.buffer, cpu);
+ ring_buffer_record_disable_cpu(tr->snapshot_buffer.buffer, cpu);
#endif
}
if (!cpumask_test_cpu(cpu, tr->tracing_cpumask) &&
cpumask_test_cpu(cpu, tracing_cpumask_new)) {
ring_buffer_record_enable_cpu(tr->array_buffer.buffer, cpu);
#ifdef CONFIG_TRACER_MAX_TRACE
- ring_buffer_record_enable_cpu(tr->max_buffer.buffer, cpu);
+ ring_buffer_record_enable_cpu(tr->snapshot_buffer.buffer, cpu);
#endif
}
}
@@ -4576,7 +4576,7 @@ int set_tracer_flag(struct trace_array *tr, u64 mask, int enabled)
case TRACE_ITER(OVERWRITE):
ring_buffer_change_overwrite(tr->array_buffer.buffer, enabled);
#ifdef CONFIG_TRACER_MAX_TRACE
- ring_buffer_change_overwrite(tr->max_buffer.buffer, enabled);
+ ring_buffer_change_overwrite(tr->snapshot_buffer.buffer, enabled);
#endif
break;
@@ -5294,7 +5294,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
if (!tr->allocated_snapshot)
goto out;
- ret = ring_buffer_resize(tr->max_buffer.buffer, size, cpu);
+ ret = ring_buffer_resize(tr->snapshot_buffer.buffer, size, cpu);
if (ret < 0) {
int r = resize_buffer_duplicate_size(&tr->array_buffer,
&tr->array_buffer, cpu);
@@ -5319,7 +5319,7 @@ static int __tracing_resize_ring_buffer(struct trace_array *tr,
goto out_start;
}
- update_buffer_entries(&tr->max_buffer, cpu);
+ update_buffer_entries(&tr->snapshot_buffer, cpu);
out:
#endif /* CONFIG_TRACER_MAX_TRACE */
@@ -7036,9 +7036,9 @@ int tracing_set_clock(struct trace_array *tr, const char *clockstr)
tracing_reset_online_cpus(&tr->array_buffer);
#ifdef CONFIG_TRACER_MAX_TRACE
- if (tr->max_buffer.buffer)
- ring_buffer_set_clock(tr->max_buffer.buffer, trace_clocks[i].func);
- tracing_reset_online_cpus(&tr->max_buffer);
+ if (tr->snapshot_buffer.buffer)
+ ring_buffer_set_clock(tr->snapshot_buffer.buffer, trace_clocks[i].func);
+ tracing_reset_online_cpus(&tr->snapshot_buffer);
#endif
if (tr->scratch && !(tr->flags & TRACE_ARRAY_FL_LAST_BOOT)) {
@@ -7170,7 +7170,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
ret = 0;
iter->tr = tr;
- iter->array_buffer = &tr->max_buffer;
+ iter->array_buffer = &tr->snapshot_buffer;
iter->cpu_file = tracing_get_cpu(inode);
m->private = iter;
file->private_data = m;
@@ -7233,7 +7233,7 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
return -EINVAL;
#endif
if (tr->allocated_snapshot)
- ret = resize_buffer_duplicate_size(&tr->max_buffer,
+ ret = resize_buffer_duplicate_size(&tr->snapshot_buffer,
&tr->array_buffer, iter->cpu_file);
ret = tracing_arm_snapshot_locked(tr);
@@ -7254,9 +7254,9 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
default:
if (tr->allocated_snapshot) {
if (iter->cpu_file == RING_BUFFER_ALL_CPUS)
- tracing_reset_online_cpus(&tr->max_buffer);
+ tracing_reset_online_cpus(&tr->snapshot_buffer);
else
- tracing_reset_cpu(&tr->max_buffer, iter->cpu_file);
+ tracing_reset_cpu(&tr->snapshot_buffer, iter->cpu_file);
}
break;
}
@@ -7312,7 +7312,7 @@ static int snapshot_raw_open(struct inode *inode, struct file *filp)
}
info->iter.snapshot = true;
- info->iter.array_buffer = &info->iter.tr->max_buffer;
+ info->iter.array_buffer = &info->iter.tr->snapshot_buffer;
return ret;
}
@@ -9195,7 +9195,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf,
if (!tr->allocated_snapshot)
goto out_max;
- ret = ring_buffer_subbuf_order_set(tr->max_buffer.buffer, order);
+ ret = ring_buffer_subbuf_order_set(tr->snapshot_buffer.buffer, order);
if (ret) {
/* Put back the old order */
cnt = ring_buffer_subbuf_order_set(tr->array_buffer.buffer, old_order);
@@ -9416,7 +9416,7 @@ static int allocate_trace_buffers(struct trace_array *tr, int size)
if (tr->range_addr_start)
return 0;
- ret = allocate_trace_buffer(tr, &tr->max_buffer,
+ ret = allocate_trace_buffer(tr, &tr->snapshot_buffer,
allocate_snapshot ? size : 1);
if (MEM_FAIL(ret, "Failed to allocate trace buffer\n")) {
free_trace_buffer(&tr->array_buffer);
@@ -9439,7 +9439,7 @@ static void free_trace_buffers(struct trace_array *tr)
kfree(tr->module_delta);
#ifdef CONFIG_TRACER_MAX_TRACE
- free_trace_buffer(&tr->max_buffer);
+ free_trace_buffer(&tr->snapshot_buffer);
#endif
}
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 6b0fedf2f532..b50383aa8e50 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -331,17 +331,18 @@ struct trace_array {
struct array_buffer array_buffer;
#ifdef CONFIG_TRACER_MAX_TRACE
/*
- * The max_buffer is used to snapshot the trace when a maximum
+ * The snapshot_buffer is used to snapshot the trace when a maximum
* latency is reached, or when the user initiates a snapshot.
* Some tracers will use this to store a maximum trace while
* it continues examining live traces.
*
- * The buffers for the max_buffer are set up the same as the array_buffer
- * When a snapshot is taken, the buffer of the max_buffer is swapped
- * with the buffer of the array_buffer and the buffers are reset for
- * the array_buffer so the tracing can continue.
+ * The buffers for the snapshot_buffer are set up the same as the
+ * array_buffer. When a snapshot is taken, the buffer of the
+ * snapshot_buffer is swapped with the buffer of the array_buffer
+ * and the buffers are reset for the array_buffer so the tracing can
+ * continue.
*/
- struct array_buffer max_buffer;
+ struct array_buffer snapshot_buffer;
bool allocated_snapshot;
spinlock_t snapshot_trigger_lock;
unsigned int snapshot;
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index d88c44f1dfa5..be53fe6fee6a 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -1225,7 +1225,7 @@ trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
/* check both trace buffers */
ret = trace_test_buffer(&tr->array_buffer, NULL);
if (!ret)
- ret = trace_test_buffer(&tr->max_buffer, &count);
+ ret = trace_test_buffer(&tr->snapshot_buffer, &count);
trace->reset(tr);
tracing_start();
@@ -1287,7 +1287,7 @@ trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
/* check both trace buffers */
ret = trace_test_buffer(&tr->array_buffer, NULL);
if (!ret)
- ret = trace_test_buffer(&tr->max_buffer, &count);
+ ret = trace_test_buffer(&tr->snapshot_buffer, &count);
trace->reset(tr);
tracing_start();
@@ -1355,7 +1355,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
if (ret)
goto out;
- ret = trace_test_buffer(&tr->max_buffer, &count);
+ ret = trace_test_buffer(&tr->snapshot_buffer, &count);
if (ret)
goto out;
@@ -1385,7 +1385,7 @@ trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *
if (ret)
goto out;
- ret = trace_test_buffer(&tr->max_buffer, &count);
+ ret = trace_test_buffer(&tr->snapshot_buffer, &count);
if (!ret && !count) {
printk(KERN_CONT ".. no entries found ..");
@@ -1513,7 +1513,7 @@ trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
/* check both trace buffers */
ret = trace_test_buffer(&tr->array_buffer, NULL);
if (!ret)
- ret = trace_test_buffer(&tr->max_buffer, &count);
+ ret = trace_test_buffer(&tr->snapshot_buffer, &count);
trace->reset(tr);
--
2.51.0
^ permalink raw reply related
* [PATCH v3 0/3] tracing: Clean up the snapshot and max tracer code
From: Steven Rostedt @ 2026-02-08 18:38 UTC (permalink / raw)
To: linux-kernel, linux-trace-kernel
Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton
When tracing first was added it had latency tracers that used a separate
snapshot buffer to swap the current buffer being written to with a static
buffer that is only read. This later became a feature that user space could
use by attaching to the latency tracer snapshot buffer. But the buffer was
named max_buffer which is not what it is used for in all cases.
Rename the max_buffer name to snapshot_buffer.
The "use_max_tr" field of the tracer structure is only defined when
CONFIG_TRACER_MAX_TRACE is defined. To get rid of some of the #ifdefs in the
code around accesses of that field, use a helper function
tracer_uses_snapshot() that access the field when the config is defined, or
returns false if not.
Finally, since the latency tracers use the snapshot buffer and snapshot
buffers do not need latency tracers, have the TRACER_MAX_TRACE config select
TRACE_SNAPSHOT config and not the other way around. Also clean up the code
to properly protect the max tracer references and the snapshot references.
Changes since v2: https://lore.kernel.org/all/20260208040156.005531619@kernel.org/
- Fix tracing_set_tracer() when CONFIG_TRACER_SNAPSHOT is not enabled.
Seems that some fields that are only available with that config were
still exposed, and the local variable used was still hidden.
(kernel test robot)
- Fix trace_create_maxlat_file() declaration when CONFIG_TRACER_SNAPSHOT
is not defined.
Changes since v1: https://lore.kernel.org/linux-trace-kernel/20260206193741.767171392@kernel.org/
- This separates the updates to snapshot buffer and max tracers from
the last series. It was a rewrite.
Steven Rostedt (3):
tracing: Rename trace_array field max_buffer to snapshot_buffer
tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
tracing: Better separate SNAPSHOT and MAX_TRACE options
----
kernel/trace/Kconfig | 8 +-
kernel/trace/trace.c | 192 +++++++++++++++++++-----------------------
kernel/trace/trace.h | 44 +++++++---
kernel/trace/trace_selftest.c | 10 +--
4 files changed, 127 insertions(+), 127 deletions(-)
^ permalink raw reply
* Re: [PATCH 2/2] tracing: resolve enum names for function arguments via BTF
From: Steven Rostedt @ 2026-02-08 16:47 UTC (permalink / raw)
To: Donglin Peng
Cc: Alexei Starovoitov, Andrii Nakryiko, Alexei Starovoitov,
Masami Hiramatsu, LKML, Donglin Peng, linux-trace-kernel, bpf,
Eduard Zingerman, Yordan Karadzhov
In-Reply-To: <CAErzpmu3XGE=LKQjGgb_538BV=hytkv4rsE_M2r6ADEkB_Ckkw@mail.gmail.com>
On Sun, 8 Feb 2026 23:42:50 +0800
Donglin Peng <dolinux.peng@gmail.com> wrote:
> I hope future versions of `trace-cmd` or `Kernelshark` could incorporate
> similar features to enhance trace analysis workflows.
Hey, they are both open source projects. Patches welcomed ;-)
Note, trace-cmd is mostly a side project for me. I mostly work on it in
my spare time (or in the plane while I travel). Which explains why it
doesn't get the loving it deserves.
KernelShark is now maintained by Yordan Karadzhov, which I believe he's
in the same predicament as I am. He too is open for patches.
-- Steve
^ permalink raw reply
* Re: [PATCH 2/2] tracing: resolve enum names for function arguments via BTF
From: Donglin Peng @ 2026-02-08 15:42 UTC (permalink / raw)
To: Steven Rostedt
Cc: Alexei Starovoitov, Andrii Nakryiko, Alexei Starovoitov,
Masami Hiramatsu, LKML, Donglin Peng, linux-trace-kernel, bpf,
Eduard Zingerman
In-Reply-To: <20260208102742.2169de7a@robin>
On Sun, Feb 8, 2026 at 11:27 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Sun, 8 Feb 2026 21:07:37 +0800
> Donglin Peng <dolinux.peng@gmail.com> wrote:
> > Hi Steve,
> >
> > I noticed that trace-cmd 3.4 introduced a new feature:
> >
> > - Add support for showing parent functions in function graph
> >
> > If the "funcgraph-retaddr" option is set during function graph tracing,
> > the parent functions will now be displayed:
> >
> > preempt_count_add(val=65536); /* <-irq_enter_rcu */ (ret=0x10001)
> >
> > However, it currently only prints the caller's entry point. I suggest
> > enhancing this to include the **offset within the caller** as well. This
> > would allow tools like `faddr2line` to locate the exact call site accurately.
>
> Yeah, it makes sense to always show the offset of where it was called.
> We can add that for 3.4.1.
Thanks, I can send a patch to implement it.
>
> >
> > I implemented a tool named FuncGraph[1] to convert function_graph
> > ftrace output into an interactive HTML file. It leverages fastfaddr2line
> > to map return addresses (e.g., __sys_bpf+0x51/0x500) to their
> > corresponding call sites, such as: __sys_bpfat kernel/bpf/syscall.c:6115.
> >
> > What do you think?
>
> Sounds cool. Is this the vibe coding thing you talked about on Linked-In?
Yes. The project repository includes a sample HTML file (`sample.html`)
demonstrating the functionality — feel free to try it out.
I hope future versions of `trace-cmd` or `Kernelshark` could incorporate
similar features to enhance trace analysis workflows.
>
> -- Steve
>
> >
> > Thanks,
> > Donglin
> >
> > [1] https://github.com/pengdonglin137/FuncGraph
> >
> > >
> > > -- Steve
> > >
> > >
> > >
> > > [1] https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/tag/?h=trace-cmd-v3.4
>
^ permalink raw reply
* Re: [PATCH 2/2] tracing: resolve enum names for function arguments via BTF
From: Steven Rostedt @ 2026-02-08 15:27 UTC (permalink / raw)
To: Donglin Peng
Cc: Alexei Starovoitov, Andrii Nakryiko, Alexei Starovoitov,
Masami Hiramatsu, LKML, Donglin Peng, linux-trace-kernel, bpf,
Eduard Zingerman
In-Reply-To: <CAErzpmsajhJ45TkPx_TPwAPwN1fxO0cNYFTKFgLaosiPMo9wew@mail.gmail.com>
On Sun, 8 Feb 2026 21:07:37 +0800
Donglin Peng <dolinux.peng@gmail.com> wrote:
> Hi Steve,
>
> I noticed that trace-cmd 3.4 introduced a new feature:
>
> - Add support for showing parent functions in function graph
>
> If the "funcgraph-retaddr" option is set during function graph tracing,
> the parent functions will now be displayed:
>
> preempt_count_add(val=65536); /* <-irq_enter_rcu */ (ret=0x10001)
>
> However, it currently only prints the caller's entry point. I suggest
> enhancing this to include the **offset within the caller** as well. This
> would allow tools like `faddr2line` to locate the exact call site accurately.
Yeah, it makes sense to always show the offset of where it was called.
We can add that for 3.4.1.
>
> I implemented a tool named FuncGraph[1] to convert function_graph
> ftrace output into an interactive HTML file. It leverages fastfaddr2line
> to map return addresses (e.g., __sys_bpf+0x51/0x500) to their
> corresponding call sites, such as: __sys_bpfat kernel/bpf/syscall.c:6115.
>
> What do you think?
Sounds cool. Is this the vibe coding thing you talked about on Linked-In?
-- Steve
>
> Thanks,
> Donglin
>
> [1] https://github.com/pengdonglin137/FuncGraph
>
> >
> > -- Steve
> >
> >
> >
> > [1] https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/tag/?h=trace-cmd-v3.4
^ permalink raw reply
* Re: [PATCH 2/2] tracing: resolve enum names for function arguments via BTF
From: Donglin Peng @ 2026-02-08 13:08 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: Steven Rostedt, Andrii Nakryiko, Alexei Starovoitov,
Masami Hiramatsu, LKML, Donglin Peng, linux-trace-kernel, bpf,
Eduard Zingerman
In-Reply-To: <CAADnVQKrAcSzTYbSEHkWiWS0Ot5wAQ8_Q_v6-J=6=O4MxLpbpQ@mail.gmail.com>
On Sat, Feb 7, 2026 at 12:05 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Thu, Feb 5, 2026 at 8:10 PM Donglin Peng <dolinux.peng@gmail.com> wrote:
> >
> > On Thu, Feb 5, 2026 at 11:56 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
> > > On Thu, Feb 5, 2026 at 1:21 AM Donglin Peng <dolinux.peng@gmail.com> wrote:
> > > >
> > > > On Wed, Feb 4, 2026 at 10:52 PM Donglin Peng <dolinux.peng@gmail.com> wrote:
> > > > >
> > > > > On Wed, Feb 4, 2026 at 12:00 AM Alexei Starovoitov
> > > > > <alexei.starovoitov@gmail.com> wrote:
> > > > > >
> > > > > > On Tue, Feb 3, 2026 at 7:16 AM Steven Rostedt <rostedt@goodmis.org> wrote:
> > > > > > >
> > > > > > > On Tue, 3 Feb 2026 21:50:47 +0800
> > > > > > > Donglin Peng <dolinux.peng@gmail.com> wrote:
> > > > > > >
> > > > > > > > Testing revealed that sorting within resolve_btfids introduces issues with
> > > > > > > > btf__dedup. Therefore, I plan to move the sorting logic directly into
> > > > > > > > btf__add_enum_value and btf__add_enum64_value in libbpf, which are
> > > > > > > > invoked by pahole. However, it means that we need a newer pahole
> > > > > > > > version.
> > > > > > >
> > > > > > > Sorting isn't a requirement just something I wanted to bring up. If it's
> > > > > > > too complex and doesn't achieve much benefit then let's not do it.
> > > > > > >
> > > > > > > My worry is because "cat trace" takes quite a long time just reading the
> > > > > > > BTF arguments. I'm worried it will just get worse with enums as well.
> > > > > > >
> > > > > > > I have trace-cmd reading BTF now (just haven't officially released it) and
> > > > > > > doing an extract and reading the trace.dat file is much faster than reading
> > > > > > > the trace file with arguments. I'll need to implement the enum logic too in
> > > > > > > libtraceevent.
> > > > > >
> > > > > > If you mean to do pretty printing of the trace in user space then +1 from me.
> > > > > >
> > > > > > I don't like sorting enums either in resolve_btfid, pahole or kernel.
> > > > > > Sorted BTF by name was ok, since it doesn't change original semantics.
> > > > > > While sorting enums by value gets us to the grey zone where
> > > > > > the sequence of enum names in vmlinux.h becomes different than in dwarf.
> > > > >
> > > > > Thanks, I agreed.
> > > > >
> > > > > >
> > > > > > Also id->name mapping in general is not precise.
> > > > > > There is no requirement for enums to be unique.
> > > > > > Just grabbing the first one:
> > > > > > ATA_PIO0 = 1,
> > > > > > ATA_PIO1 = 3,
> > > > > > ATA_PIO2 = 7,
> > > > > > ATA_UDMA0 = 1,
> > > > > > ATA_UDMA1 = 3,
> > > > > > ATA_UDMA2 = 7,
> > > > > > ATA_ID_CYLS = 1,
> > > > > > ATA_ID_HEADS = 3,
> > > > > > SCR_ERROR = 1,
> > > > > > SCR_CONTROL = 2,
> > > > > > SCR_ACTIVE = 3,
> > > > > >
> > > > > > All these names are part of the same enum type.
> > > > > > Which one to print? First one?
> > > >
> > > > Another option is to print all matching entries, incurring increased
> > > > overhead and extended trace log length. However, I prefer printing
> > > > the first matching entry, though it might be inaccurate in rare cases.
> > >
> > > I disagree. It's not rare.
> > > I wouldn't print anything. Let user space deal with it.
> >
> > Okay, I will implement this in libtraceevent first. By the way, would the first
> > patch [1] introducing the for_each_enumand for_each_enum64 helper
> > macros be acceptable?
> >
> > [1] https://lore.kernel.org/lkml/20260202111548.3555306-2-dolinux.peng@gmail.com/
>
> Just that patch alone? What's the point?
> Refactor for what? Does it read better? No.
Thanks, I see.
^ permalink raw reply
* Re: [PATCH 2/2] tracing: resolve enum names for function arguments via BTF
From: Donglin Peng @ 2026-02-08 13:07 UTC (permalink / raw)
To: Steven Rostedt
Cc: Alexei Starovoitov, Andrii Nakryiko, Alexei Starovoitov,
Masami Hiramatsu, LKML, Donglin Peng, linux-trace-kernel, bpf,
Eduard Zingerman
In-Reply-To: <20260205130459.0ff532f3@robin>
On Fri, Feb 6, 2026 at 2:05 AM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 4 Feb 2026 22:52:11 +0800
> Donglin Peng <dolinux.peng@gmail.com> wrote:
>
> > > > I have trace-cmd reading BTF now (just haven't officially released it) and
> > > > doing an extract and reading the trace.dat file is much faster than reading
> > > > the trace file with arguments. I'll need to implement the enum logic too in
> > > > libtraceevent.
> > >
> > > If you mean to do pretty printing of the trace in user space then +1 from me.
> > >
> > > I don't like sorting enums either in resolve_btfid, pahole or kernel.
> > > Sorted BTF by name was ok, since it doesn't change original semantics.
> > > While sorting enums by value gets us to the grey zone where
> > > the sequence of enum names in vmlinux.h becomes different than in dwarf.
> >
> > Thanks, I agreed.
>
> BTW, I just officially released trace-cmd v3.4 (where you can see whats
> new in that release here[1]).
>
> The biggest change is that it saves the BTF file in the trace.dat file
> and parses it on the report (it requires libtraceevent v1.9):
>
> ~# trace-cmd record -p function_graph -O funcgraph-args -g do_sys_openat2
> [..]
> ~# trace-cmd report
> trace-cmd-50935 [002] ...1. 3490.518138: funcgraph_entry: | do_sys_openat2(dfd=4294967196, filename=0x557bb9e3ee10, how=0xffff88815220fea8) {
> trace-cmd-50935 [002] ...1. 3490.518141: funcgraph_entry: | getname_flags(filename=0x557bb9e3ee10, flags=0) {
> trace-cmd-50935 [002] ...1. 3490.518142: funcgraph_entry: | getname_flags.part.0(filename=0x557bb9e3ee10, flags=0) {
> trace-cmd-50935 [002] ...1. 3490.518143: funcgraph_entry: | kmem_cache_alloc_noprof(s=0xffff888106c7e000, gfpflags=0xcc0) {
> trace-cmd-50935 [002] ...1. 3490.518145: funcgraph_entry: | stack_trace_save(store=0xffff88815220fac8, size=0x40, skipnr=0x0) {
> trace-cmd-50935 [002] ...1. 3490.518147: funcgraph_entry: | arch_stack_walk(consume_entry=0xffffffff94d9dfe0, cookie=0xffff88815220fa58, task=0xffff88812d4c3580, regs=0x0) {
> trace-cmd-50935 [002] ...1. 3490.518148: funcgraph_entry: | __unwind_start(state=0xffff88815220f988, task=0xffff88812d4c3580, regs=0x0, first_frame=0xffff88815220fa28) {
> trace-cmd-50935 [002] ...1. 3490.518149: funcgraph_entry: 1.518 us | get_stack_info(stack=0xffff88815220f938, task=0xffff88812d4c3580, info=0xffff88815220f988, visit_mask=0xffff88815220f9a8); (ret=0x0)
> trace-cmd-50935 [002] ...1. 3490.518152: funcgraph_entry: | unwind_next_frame(state=0xffff88815220f988) {
> trace-cmd-50935 [002] ...1. 3490.518153: funcgraph_entry: 0.951 us | __rcu_read_lock(); (ret=0xffff88812d4c3580)
Hi Steve,
I noticed that trace-cmd 3.4 introduced a new feature:
- Add support for showing parent functions in function graph
If the "funcgraph-retaddr" option is set during function graph tracing,
the parent functions will now be displayed:
preempt_count_add(val=65536); /* <-irq_enter_rcu */ (ret=0x10001)
However, it currently only prints the caller's entry point. I suggest
enhancing this to include the **offset within the caller** as well. This
would allow tools like `faddr2line` to locate the exact call site accurately.
I implemented a tool named FuncGraph[1] to convert function_graph
ftrace output into an interactive HTML file. It leverages fastfaddr2line
to map return addresses (e.g., __sys_bpf+0x51/0x500) to their
corresponding call sites, such as: __sys_bpfat kernel/bpf/syscall.c:6115.
What do you think?
Thanks,
Donglin
[1] https://github.com/pengdonglin137/FuncGraph
>
> -- Steve
>
>
>
> [1] https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git/tag/?h=trace-cmd-v3.4
^ permalink raw reply
* Re: [PATCH v2 2/3] tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
From: kernel test robot @ 2026-02-08 12:24 UTC (permalink / raw)
To: Steven Rostedt, linux-kernel, linux-trace-kernel
Cc: llvm, oe-kbuild-all, Masami Hiramatsu, Mark Rutland,
Mathieu Desnoyers, Andrew Morton, Linux Memory Management List
In-Reply-To: <20260208040221.900653834@kernel.org>
Hi Steven,
kernel test robot noticed the following build errors:
[auto build test ERROR on trace/for-next]
[also build test ERROR on linus/master v6.19-rc8 next-20260205]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Rename-trace_array-field-max_buffer-to-snapshot_buffer/20260208-120355
base: https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link: https://lore.kernel.org/r/20260208040221.900653834%40kernel.org
patch subject: [PATCH v2 2/3] tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260208/202602082013.PnPZCdsA-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260208/202602082013.PnPZCdsA-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602082013.PnPZCdsA-lkp@intel.com/
All errors (new ones prefixed by >>):
>> kernel/trace/trace.c:6337:13: error: no member named 'cond_snapshot' in 'struct trace_array'
6337 | ret = tr->cond_snapshot ? -EBUSY : 0;
| ~~ ^
kernel/trace/trace.c:6366:2: error: use of undeclared identifier 'had_max_tr'
6366 | had_max_tr = tracer_uses_snapshot(tr->current_trace);
| ^
kernel/trace/trace.c:6372:6: error: use of undeclared identifier 'had_max_tr'
6372 | if (had_max_tr && !tracer_uses_snapshot(trace)) {
| ^
kernel/trace/trace.c:6385:7: error: use of undeclared identifier 'had_max_tr'
6385 | if (!had_max_tr && tracer_uses_snapshot(trace)) {
| ^
kernel/trace/trace.c:9795:23: warning: shift count is negative [-Wshift-count-negative]
9795 | !((1ULL << i) & TOP_LEVEL_TRACE_FLAGS)) {
| ^~~~~~~~~~~~~~~~~~~~~
kernel/trace/trace.c:523:9: note: expanded from macro 'TOP_LEVEL_TRACE_FLAGS'
523 | TRACE_ITER(PROF_TEXT_OFFSET) | FPROFILE_DEFAULT_FLAGS)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/trace/trace.h:1452:42: note: expanded from macro 'TRACE_ITER'
1452 | (TRACE_ITER_##flag##_BIT < 0 ? 0 : 1ULL << (TRACE_ITER_##flag##_BIT))
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning and 4 errors generated.
vim +6337 kernel/trace/trace.c
ef9188bcc6ca1d Mark-PK Tsai 2022-04-26 6300
9c5b9d3d65e485 Masami Hiramatsu 2020-01-11 6301 int tracing_set_tracer(struct trace_array *tr, const char *buf)
09d23a1d8a82e8 Steven Rostedt (Red Hat 2015-02-03 6302) {
428add559b6923 Steven Rostedt 2025-11-11 6303 struct tracer *trace = NULL;
428add559b6923 Steven Rostedt 2025-11-11 6304 struct tracers *t;
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6305) #ifdef CONFIG_TRACER_MAX_TRACE
34600f0e9c33c9 Steven Rostedt 2013-01-22 6306 bool had_max_tr;
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6307) #endif
d33b10c0c73adc Steven Rostedt 2024-12-24 6308 int ret;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6309
d33b10c0c73adc Steven Rostedt 2024-12-24 6310 guard(mutex)(&trace_types_lock);
1027fcb206a0fb Steven Rostedt 2009-03-12 6311
7a1d1e4b9639ff Steven Rostedt (Google 2024-06-12 6312) update_last_data(tr);
7a1d1e4b9639ff Steven Rostedt (Google 2024-06-12 6313)
a1f157c7a3bb34 Zheng Yejian 2023-09-06 6314 if (!tr->ring_buffer_expanded) {
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6315 ret = __tracing_resize_ring_buffer(tr, trace_buf_size,
438ced1720b584 Vaibhav Nagarnaik 2012-02-02 6316 RING_BUFFER_ALL_CPUS);
73c5162aa362a5 Steven Rostedt 2009-03-11 6317 if (ret < 0)
d33b10c0c73adc Steven Rostedt 2024-12-24 6318 return ret;
73c5162aa362a5 Steven Rostedt 2009-03-11 6319 ret = 0;
73c5162aa362a5 Steven Rostedt 2009-03-11 6320 }
73c5162aa362a5 Steven Rostedt 2009-03-11 6321
428add559b6923 Steven Rostedt 2025-11-11 6322 list_for_each_entry(t, &tr->tracers, list) {
428add559b6923 Steven Rostedt 2025-11-11 6323 if (strcmp(t->tracer->name, buf) == 0) {
428add559b6923 Steven Rostedt 2025-11-11 6324 trace = t->tracer;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6325 break;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6326 }
428add559b6923 Steven Rostedt 2025-11-11 6327 }
428add559b6923 Steven Rostedt 2025-11-11 6328 if (!trace)
d33b10c0c73adc Steven Rostedt 2024-12-24 6329 return -EINVAL;
d33b10c0c73adc Steven Rostedt 2024-12-24 6330
428add559b6923 Steven Rostedt 2025-11-11 6331 if (trace == tr->current_trace)
d33b10c0c73adc Steven Rostedt 2024-12-24 6332 return 0;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6333
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6334 if (tracer_uses_snapshot(trace)) {
c0a581d7126c0b Waiman Long 2022-09-22 6335 local_irq_disable();
a35873a0993b4d Tom Zanussi 2019-02-13 6336 arch_spin_lock(&tr->max_lock);
22bec11a569983 Steven Rostedt 2025-01-06 @6337 ret = tr->cond_snapshot ? -EBUSY : 0;
a35873a0993b4d Tom Zanussi 2019-02-13 6338 arch_spin_unlock(&tr->max_lock);
c0a581d7126c0b Waiman Long 2022-09-22 6339 local_irq_enable();
a35873a0993b4d Tom Zanussi 2019-02-13 6340 if (ret)
d33b10c0c73adc Steven Rostedt 2024-12-24 6341 return ret;
a35873a0993b4d Tom Zanussi 2019-02-13 6342 }
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6343
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6344) /* Some tracers won't work on kernel command line */
428add559b6923 Steven Rostedt 2025-11-11 6345 if (system_state < SYSTEM_RUNNING && trace->noboot) {
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6346) pr_warn("Tracer '%s' is not allowed on command line, ignored\n",
428add559b6923 Steven Rostedt 2025-11-11 6347 trace->name);
d1e27ee9c6f21c Steven Rostedt 2024-12-19 6348 return -EINVAL;
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6349) }
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6350)
607e2ea167e56d Steven Rostedt (Red Hat 2013-11-06 6351) /* Some tracers are only allowed for the top level buffer */
428add559b6923 Steven Rostedt 2025-11-11 6352 if (!trace_ok_for_array(trace, tr))
d33b10c0c73adc Steven Rostedt 2024-12-24 6353 return -EINVAL;
607e2ea167e56d Steven Rostedt (Red Hat 2013-11-06 6354)
cf6ab6d9143b15 Steven Rostedt (Red Hat 2014-12-15 6355) /* If trace pipe files are being read, we can't change the tracer */
d33b10c0c73adc Steven Rostedt 2024-12-24 6356 if (tr->trace_ref)
d33b10c0c73adc Steven Rostedt 2024-12-24 6357 return -EBUSY;
cf6ab6d9143b15 Steven Rostedt (Red Hat 2014-12-15 6358)
9f029e83e968e5 Steven Rostedt 2008-11-12 6359 trace_branch_disable();
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6360)
50512ab576e1ce Steven Rostedt (Red Hat 2014-01-14 6361) tr->current_trace->enabled--;
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6362)
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6363 if (tr->current_trace->reset)
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6364 tr->current_trace->reset(tr);
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6365)
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6366 had_max_tr = tracer_uses_snapshot(tr->current_trace);
a541a9559bb0a8 Steven Rostedt (Google 2022-10-05 6367)
7440172974e85b Paul E. McKenney 2018-11-06 6368 /* Current trace needs to be nop_trace before synchronize_rcu */
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6369 tr->current_trace = &nop_trace;
428add559b6923 Steven Rostedt 2025-11-11 6370 tr->current_trace_flags = nop_trace.flags;
34600f0e9c33c9 Steven Rostedt 2013-01-22 6371
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6372 if (had_max_tr && !tracer_uses_snapshot(trace)) {
34600f0e9c33c9 Steven Rostedt 2013-01-22 6373 /*
34600f0e9c33c9 Steven Rostedt 2013-01-22 6374 * We need to make sure that the update_max_tr sees that
34600f0e9c33c9 Steven Rostedt 2013-01-22 6375 * current_trace changed to nop_trace to keep it from
34600f0e9c33c9 Steven Rostedt 2013-01-22 6376 * swapping the buffers after we resize it.
34600f0e9c33c9 Steven Rostedt 2013-01-22 6377 * The update_max_tr is called from interrupts disabled
34600f0e9c33c9 Steven Rostedt 2013-01-22 6378 * so a synchronized_sched() is sufficient.
34600f0e9c33c9 Steven Rostedt 2013-01-22 6379 */
7440172974e85b Paul E. McKenney 2018-11-06 6380 synchronize_rcu();
3209cff4490bee Steven Rostedt (Red Hat 2013-03-12 6381) free_snapshot(tr);
180e4e390978af Vincent Donnefort 2024-02-20 6382 tracing_disarm_snapshot(tr);
ef710e100c1068 KOSAKI Motohiro 2010-07-01 6383 }
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6384)
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6385 if (!had_max_tr && tracer_uses_snapshot(trace)) {
180e4e390978af Vincent Donnefort 2024-02-20 6386 ret = tracing_arm_snapshot_locked(tr);
180e4e390978af Vincent Donnefort 2024-02-20 6387 if (ret)
d33b10c0c73adc Steven Rostedt 2024-12-24 6388 return ret;
ef710e100c1068 KOSAKI Motohiro 2010-07-01 6389 }
577b785f55168d Steven Rostedt 2009-02-26 6390
428add559b6923 Steven Rostedt 2025-11-11 6391 tr->current_trace_flags = t->flags ? : t->tracer->flags;
428add559b6923 Steven Rostedt 2025-11-11 6392
428add559b6923 Steven Rostedt 2025-11-11 6393 if (trace->init) {
428add559b6923 Steven Rostedt 2025-11-11 6394 ret = tracer_init(trace, tr);
180e4e390978af Vincent Donnefort 2024-02-20 6395 if (ret) {
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6396 if (tracer_uses_snapshot(trace))
180e4e390978af Vincent Donnefort 2024-02-20 6397 tracing_disarm_snapshot(tr);
428add559b6923 Steven Rostedt 2025-11-11 6398 tr->current_trace_flags = nop_trace.flags;
d33b10c0c73adc Steven Rostedt 2024-12-24 6399 return ret;
1c80025a49855b Frederic Weisbecker 2008-11-16 6400 }
180e4e390978af Vincent Donnefort 2024-02-20 6401 }
bc0c38d139ec7f Steven Rostedt 2008-05-12 6402
428add559b6923 Steven Rostedt 2025-11-11 6403 tr->current_trace = trace;
50512ab576e1ce Steven Rostedt (Red Hat 2014-01-14 6404) tr->current_trace->enabled++;
9f029e83e968e5 Steven Rostedt 2008-11-12 6405 trace_branch_enable(tr);
bc0c38d139ec7f Steven Rostedt 2008-05-12 6406
d33b10c0c73adc Steven Rostedt 2024-12-24 6407 return 0;
d9e540762f5cdd Peter Zijlstra 2008-11-01 6408 }
d9e540762f5cdd Peter Zijlstra 2008-11-01 6409
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply
* Re: [PATCH v2 2/3] tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
From: kernel test robot @ 2026-02-08 11:22 UTC (permalink / raw)
To: Steven Rostedt, linux-kernel, linux-trace-kernel
Cc: oe-kbuild-all, Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers,
Andrew Morton, Linux Memory Management List
In-Reply-To: <20260208040221.900653834@kernel.org>
Hi Steven,
kernel test robot noticed the following build errors:
[auto build test ERROR on trace/for-next]
[also build test ERROR on linus/master v6.19-rc8 next-20260205]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Rename-trace_array-field-max_buffer-to-snapshot_buffer/20260208-120355
base: https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link: https://lore.kernel.org/r/20260208040221.900653834%40kernel.org
patch subject: [PATCH v2 2/3] tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
config: sh-defconfig (https://download.01.org/0day-ci/archive/20260208/202602081945.dguj4FF6-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260208/202602081945.dguj4FF6-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602081945.dguj4FF6-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/trace/trace.c: In function 'tracing_set_tracer':
>> kernel/trace/trace.c:6337:25: error: 'struct trace_array' has no member named 'cond_snapshot'
6337 | ret = tr->cond_snapshot ? -EBUSY : 0;
| ^~
kernel/trace/trace.c:6366:9: error: 'had_max_tr' undeclared (first use in this function)
6366 | had_max_tr = tracer_uses_snapshot(tr->current_trace);
| ^~~~~~~~~~
kernel/trace/trace.c:6366:9: note: each undeclared identifier is reported only once for each function it appears in
vim +6337 kernel/trace/trace.c
ef9188bcc6ca1d Mark-PK Tsai 2022-04-26 6300
9c5b9d3d65e485 Masami Hiramatsu 2020-01-11 6301 int tracing_set_tracer(struct trace_array *tr, const char *buf)
09d23a1d8a82e8 Steven Rostedt (Red Hat 2015-02-03 6302) {
428add559b6923 Steven Rostedt 2025-11-11 6303 struct tracer *trace = NULL;
428add559b6923 Steven Rostedt 2025-11-11 6304 struct tracers *t;
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6305) #ifdef CONFIG_TRACER_MAX_TRACE
34600f0e9c33c9 Steven Rostedt 2013-01-22 6306 bool had_max_tr;
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6307) #endif
d33b10c0c73adc Steven Rostedt 2024-12-24 6308 int ret;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6309
d33b10c0c73adc Steven Rostedt 2024-12-24 6310 guard(mutex)(&trace_types_lock);
1027fcb206a0fb Steven Rostedt 2009-03-12 6311
7a1d1e4b9639ff Steven Rostedt (Google 2024-06-12 6312) update_last_data(tr);
7a1d1e4b9639ff Steven Rostedt (Google 2024-06-12 6313)
a1f157c7a3bb34 Zheng Yejian 2023-09-06 6314 if (!tr->ring_buffer_expanded) {
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6315 ret = __tracing_resize_ring_buffer(tr, trace_buf_size,
438ced1720b584 Vaibhav Nagarnaik 2012-02-02 6316 RING_BUFFER_ALL_CPUS);
73c5162aa362a5 Steven Rostedt 2009-03-11 6317 if (ret < 0)
d33b10c0c73adc Steven Rostedt 2024-12-24 6318 return ret;
73c5162aa362a5 Steven Rostedt 2009-03-11 6319 ret = 0;
73c5162aa362a5 Steven Rostedt 2009-03-11 6320 }
73c5162aa362a5 Steven Rostedt 2009-03-11 6321
428add559b6923 Steven Rostedt 2025-11-11 6322 list_for_each_entry(t, &tr->tracers, list) {
428add559b6923 Steven Rostedt 2025-11-11 6323 if (strcmp(t->tracer->name, buf) == 0) {
428add559b6923 Steven Rostedt 2025-11-11 6324 trace = t->tracer;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6325 break;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6326 }
428add559b6923 Steven Rostedt 2025-11-11 6327 }
428add559b6923 Steven Rostedt 2025-11-11 6328 if (!trace)
d33b10c0c73adc Steven Rostedt 2024-12-24 6329 return -EINVAL;
d33b10c0c73adc Steven Rostedt 2024-12-24 6330
428add559b6923 Steven Rostedt 2025-11-11 6331 if (trace == tr->current_trace)
d33b10c0c73adc Steven Rostedt 2024-12-24 6332 return 0;
bc0c38d139ec7f Steven Rostedt 2008-05-12 6333
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6334 if (tracer_uses_snapshot(trace)) {
c0a581d7126c0b Waiman Long 2022-09-22 6335 local_irq_disable();
a35873a0993b4d Tom Zanussi 2019-02-13 6336 arch_spin_lock(&tr->max_lock);
22bec11a569983 Steven Rostedt 2025-01-06 @6337 ret = tr->cond_snapshot ? -EBUSY : 0;
a35873a0993b4d Tom Zanussi 2019-02-13 6338 arch_spin_unlock(&tr->max_lock);
c0a581d7126c0b Waiman Long 2022-09-22 6339 local_irq_enable();
a35873a0993b4d Tom Zanussi 2019-02-13 6340 if (ret)
d33b10c0c73adc Steven Rostedt 2024-12-24 6341 return ret;
a35873a0993b4d Tom Zanussi 2019-02-13 6342 }
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6343
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6344) /* Some tracers won't work on kernel command line */
428add559b6923 Steven Rostedt 2025-11-11 6345 if (system_state < SYSTEM_RUNNING && trace->noboot) {
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6346) pr_warn("Tracer '%s' is not allowed on command line, ignored\n",
428add559b6923 Steven Rostedt 2025-11-11 6347 trace->name);
d1e27ee9c6f21c Steven Rostedt 2024-12-19 6348 return -EINVAL;
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6349) }
c7b3ae0bd2ca65 Ziqian SUN (Zamir 2017-09-11 6350)
607e2ea167e56d Steven Rostedt (Red Hat 2013-11-06 6351) /* Some tracers are only allowed for the top level buffer */
428add559b6923 Steven Rostedt 2025-11-11 6352 if (!trace_ok_for_array(trace, tr))
d33b10c0c73adc Steven Rostedt 2024-12-24 6353 return -EINVAL;
607e2ea167e56d Steven Rostedt (Red Hat 2013-11-06 6354)
cf6ab6d9143b15 Steven Rostedt (Red Hat 2014-12-15 6355) /* If trace pipe files are being read, we can't change the tracer */
d33b10c0c73adc Steven Rostedt 2024-12-24 6356 if (tr->trace_ref)
d33b10c0c73adc Steven Rostedt 2024-12-24 6357 return -EBUSY;
cf6ab6d9143b15 Steven Rostedt (Red Hat 2014-12-15 6358)
9f029e83e968e5 Steven Rostedt 2008-11-12 6359 trace_branch_disable();
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6360)
50512ab576e1ce Steven Rostedt (Red Hat 2014-01-14 6361) tr->current_trace->enabled--;
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6362)
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6363 if (tr->current_trace->reset)
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6364 tr->current_trace->reset(tr);
613f04a0f51e6e Steven Rostedt (Red Hat 2013-03-14 6365)
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6366 had_max_tr = tracer_uses_snapshot(tr->current_trace);
a541a9559bb0a8 Steven Rostedt (Google 2022-10-05 6367)
7440172974e85b Paul E. McKenney 2018-11-06 6368 /* Current trace needs to be nop_trace before synchronize_rcu */
2b6080f28c7cc3 Steven Rostedt 2012-05-11 6369 tr->current_trace = &nop_trace;
428add559b6923 Steven Rostedt 2025-11-11 6370 tr->current_trace_flags = nop_trace.flags;
34600f0e9c33c9 Steven Rostedt 2013-01-22 6371
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6372 if (had_max_tr && !tracer_uses_snapshot(trace)) {
34600f0e9c33c9 Steven Rostedt 2013-01-22 6373 /*
34600f0e9c33c9 Steven Rostedt 2013-01-22 6374 * We need to make sure that the update_max_tr sees that
34600f0e9c33c9 Steven Rostedt 2013-01-22 6375 * current_trace changed to nop_trace to keep it from
34600f0e9c33c9 Steven Rostedt 2013-01-22 6376 * swapping the buffers after we resize it.
34600f0e9c33c9 Steven Rostedt 2013-01-22 6377 * The update_max_tr is called from interrupts disabled
34600f0e9c33c9 Steven Rostedt 2013-01-22 6378 * so a synchronized_sched() is sufficient.
34600f0e9c33c9 Steven Rostedt 2013-01-22 6379 */
7440172974e85b Paul E. McKenney 2018-11-06 6380 synchronize_rcu();
3209cff4490bee Steven Rostedt (Red Hat 2013-03-12 6381) free_snapshot(tr);
180e4e390978af Vincent Donnefort 2024-02-20 6382 tracing_disarm_snapshot(tr);
ef710e100c1068 KOSAKI Motohiro 2010-07-01 6383 }
12883efb670c28 Steven Rostedt (Red Hat 2013-03-05 6384)
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6385 if (!had_max_tr && tracer_uses_snapshot(trace)) {
180e4e390978af Vincent Donnefort 2024-02-20 6386 ret = tracing_arm_snapshot_locked(tr);
180e4e390978af Vincent Donnefort 2024-02-20 6387 if (ret)
d33b10c0c73adc Steven Rostedt 2024-12-24 6388 return ret;
ef710e100c1068 KOSAKI Motohiro 2010-07-01 6389 }
577b785f55168d Steven Rostedt 2009-02-26 6390
428add559b6923 Steven Rostedt 2025-11-11 6391 tr->current_trace_flags = t->flags ? : t->tracer->flags;
428add559b6923 Steven Rostedt 2025-11-11 6392
428add559b6923 Steven Rostedt 2025-11-11 6393 if (trace->init) {
428add559b6923 Steven Rostedt 2025-11-11 6394 ret = tracer_init(trace, tr);
180e4e390978af Vincent Donnefort 2024-02-20 6395 if (ret) {
b1e5d74d04bbcf Steven Rostedt 2026-02-07 6396 if (tracer_uses_snapshot(trace))
180e4e390978af Vincent Donnefort 2024-02-20 6397 tracing_disarm_snapshot(tr);
428add559b6923 Steven Rostedt 2025-11-11 6398 tr->current_trace_flags = nop_trace.flags;
d33b10c0c73adc Steven Rostedt 2024-12-24 6399 return ret;
1c80025a49855b Frederic Weisbecker 2008-11-16 6400 }
180e4e390978af Vincent Donnefort 2024-02-20 6401 }
bc0c38d139ec7f Steven Rostedt 2008-05-12 6402
428add559b6923 Steven Rostedt 2025-11-11 6403 tr->current_trace = trace;
50512ab576e1ce Steven Rostedt (Red Hat 2014-01-14 6404) tr->current_trace->enabled++;
9f029e83e968e5 Steven Rostedt 2008-11-12 6405 trace_branch_enable(tr);
bc0c38d139ec7f Steven Rostedt 2008-05-12 6406
d33b10c0c73adc Steven Rostedt 2024-12-24 6407 return 0;
d9e540762f5cdd Peter Zijlstra 2008-11-01 6408 }
d9e540762f5cdd Peter Zijlstra 2008-11-01 6409
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply
* Re: [PATCH] tracing: Clean up use of trace_create_maxlat_file()
From: kernel test robot @ 2026-02-08 9:29 UTC (permalink / raw)
To: Steven Rostedt, LKML, Linux trace kernel
Cc: oe-kbuild-all, Masami Hiramatsu, Mathieu Desnoyers
In-Reply-To: <20260207191101.0e014abd@robin>
Hi Steven,
kernel test robot noticed the following build errors:
[auto build test ERROR on trace/for-next]
[also build test ERROR on linus/master v6.19-rc8 next-20260205]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Clean-up-use-of-trace_create_maxlat_file/20260208-081407
base: https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace for-next
patch link: https://lore.kernel.org/r/20260207191101.0e014abd%40robin
patch subject: [PATCH] tracing: Clean up use of trace_create_maxlat_file()
config: arm-randconfig-r071-20260208 (https://download.01.org/0day-ci/archive/20260208/202602081759.QQ7Yu6SK-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.5.0
smatch version: v0.5.0-8994-gd50c5a4c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260208/202602081759.QQ7Yu6SK-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602081759.QQ7Yu6SK-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/trace/trace.c: In function 'trace_create_maxlat_file':
>> kernel/trace/trace.c:1967:13: error: 'struct trace_array' has no member named 'd_max_latency'; did you mean 'max_latency'?
1967 | tr->d_max_latency = trace_create_file("tracing_max_latency",
| ^~~~~~~~~~~~~
| max_latency
vim +1967 kernel/trace/trace.c
1959
1960 static void trace_create_maxlat_file(struct trace_array *tr,
1961 struct dentry *d_tracer)
1962 {
1963 #ifdef LATENCY_FS_NOTIFY
1964 INIT_WORK(&tr->fsnotify_work, latency_fsnotify_workfn);
1965 init_irq_work(&tr->fsnotify_irqwork, latency_fsnotify_workfn_irq);
1966 #endif
> 1967 tr->d_max_latency = trace_create_file("tracing_max_latency",
1968 TRACE_MODE_WRITE,
1969 d_tracer, tr,
1970 &tracing_max_lat_fops);
1971 }
1972
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply
* Re: [PATCH v2] tracing: Clean up use of trace_create_maxlat_file()
From: Masami Hiramatsu @ 2026-02-08 4:06 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Linux trace kernel, Masami Hiramatsu, Mathieu Desnoyers
In-Reply-To: <20260206230410.4ed96e9f@robin>
On Fri, 6 Feb 2026 23:04:10 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> In trace.c, the function trace_create_maxlat_file() is defined behind the
> #ifdef CONFIG_TRACER_MAX_TRACE block. The #else part defines it as:
>
> #define trace_create_maxlat_file(tr, d_tracer) \
> trace_create_file("tracing_max_latency", TRACE_MODE_WRITE, \
> d_tracer, tr, &tracing_max_lat_fops)
>
> But the one place that it it used has:
>
> #ifdef CONFIG_TRACER_MAX_TRACE
> trace_create_maxlat_file(tr, d_tracer);
> #endif
>
> Which is pointless.
>
> Define trace_create_maxlat_file() when CONFIG_TRACER_MAX_TRACE is not
> defined as:
>
> static inline void trace_create_maxlat_file(struct trace_array *tr,
> struct dentry *d_tracer) { }
>
> And remove the #ifdef's from the code.
>
Looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thanks,
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> Changes since v1: https://patch.msgid.link/20260206121242.6cb1934d@gandalf.local.home
>
> - Fix stub function missing from !CONFIG_TRACER_MAX_TRACE
>
> kernel/trace/trace.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 6815df23e5a3..b59c237f463c 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -1969,11 +1969,8 @@ void latency_fsnotify(struct trace_array *tr)
> }
>
> #else /* !LATENCY_FS_NOTIFY */
> -
> -#define trace_create_maxlat_file(tr, d_tracer) \
> - trace_create_file("tracing_max_latency", TRACE_MODE_WRITE, \
> - d_tracer, tr, &tracing_max_lat_fops)
> -
> +static inline void trace_create_maxlat_file(struct trace_array *tr,
> + struct dentry *d_tracer) { }
> #endif
>
> /*
> @@ -2109,7 +2106,9 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
> __update_max_tr(tr, tsk, cpu);
> arch_spin_unlock(&tr->max_lock);
> }
> -
> +#else
> +static inline void trace_create_maxlat_file(struct trace_array *tr,
> + struct dentry *d_tracer) { }
> #endif /* CONFIG_TRACER_MAX_TRACE */
>
> struct pipe_wait {
> @@ -10684,9 +10683,7 @@ init_tracer_tracefs(struct trace_array *tr, struct dentry *d_tracer)
>
> create_trace_options_dir(tr);
>
> -#ifdef CONFIG_TRACER_MAX_TRACE
> trace_create_maxlat_file(tr, d_tracer);
> -#endif
>
> if (ftrace_create_function_files(tr, d_tracer))
> MEM_FAIL(1, "Could not allocate function filter files");
> --
> 2.51.0
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply
* Re: [PATCH] tracing: Have all triggers expect a file parameter
From: Masami Hiramatsu @ 2026-02-08 4:06 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Linux Trace Kernel, Masami Hiramatsu, Mathieu Desnoyers,
Tom Zanussi
In-Reply-To: <20260206101351.609d8906@gandalf.local.home>
On Fri, 6 Feb 2026 10:13:51 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> When the triggers were first created, they may not have had a file
> parameter passed to them and things needed to be done generically.
>
> But today, all triggers have a file parameter passed to them. Remove the
> generic code and add a "if (WARN_ON_ONCE(!file))" to each trigger.
>
Looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thanks,
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
> kernel/trace/trace_events_trigger.c | 62 +++++++++++------------------
> 1 file changed, 24 insertions(+), 38 deletions(-)
>
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index 06b75bcfc7b8..7fa26327c9c7 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -1347,18 +1347,13 @@ traceon_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (tracer_tracing_is_on(file->tr))
> - return;
> -
> - tracer_tracing_on(file->tr);
> + if (WARN_ON_ONCE(!file))
> return;
> - }
>
> - if (tracing_is_on())
> + if (tracer_tracing_is_on(file->tr))
> return;
>
> - tracing_on();
> + tracer_tracing_on(file->tr);
> }
>
> static bool
> @@ -1368,13 +1363,11 @@ traceon_count_func(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (tracer_tracing_is_on(file->tr))
> - return false;
> - } else {
> - if (tracing_is_on())
> - return false;
> - }
> + if (WARN_ON_ONCE(!file))
> + return false;
> +
> + if (tracer_tracing_is_on(file->tr))
> + return false;
>
> if (!data->count)
> return false;
> @@ -1392,18 +1385,13 @@ traceoff_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (!tracer_tracing_is_on(file->tr))
> - return;
> -
> - tracer_tracing_off(file->tr);
> + if (WARN_ON_ONCE(!file))
> return;
> - }
>
> - if (!tracing_is_on())
> + if (!tracer_tracing_is_on(file->tr))
> return;
>
> - tracing_off();
> + tracer_tracing_off(file->tr);
> }
>
> static bool
> @@ -1413,13 +1401,11 @@ traceoff_count_func(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file) {
> - if (!tracer_tracing_is_on(file->tr))
> - return false;
> - } else {
> - if (!tracing_is_on())
> - return false;
> - }
> + if (WARN_ON_ONCE(!file))
> + return false;
> +
> + if (!tracer_tracing_is_on(file->tr))
> + return false;
>
> if (!data->count)
> return false;
> @@ -1481,10 +1467,10 @@ snapshot_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file)
> - tracing_snapshot_instance(file->tr);
> - else
> - tracing_snapshot();
> + if (WARN_ON_ONCE(!file))
> + return;
> +
> + tracing_snapshot_instance(file->tr);
> }
>
> static int
> @@ -1570,10 +1556,10 @@ stacktrace_trigger(struct event_trigger_data *data,
> {
> struct trace_event_file *file = data->private_data;
>
> - if (file)
> - __trace_stack(file->tr, tracing_gen_ctx_dec(), STACK_SKIP);
> - else
> - trace_dump_stack(STACK_SKIP);
> + if (WARN_ON_ONCE(!file))
> + return;
> +
> + __trace_stack(file->tr, tracing_gen_ctx_dec(), STACK_SKIP);
> }
>
> static int
> --
> 2.51.0
>
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply
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