* [PATCH v2 1/2] tracing: preserve repeated boot-time tracing parameters
2026-03-09 21:27 [PATCH v2 0/2] tracing: preserve repeated boot-time parameters and drain deferred trigger frees Wesley Atwell
@ 2026-03-09 21:27 ` Wesley Atwell
2026-03-09 21:27 ` [PATCH v2 2/2] tracing: drain deferred trigger frees if kthread startup fails Wesley Atwell
1 sibling, 0 replies; 3+ messages in thread
From: Wesley Atwell @ 2026-03-09 21:27 UTC (permalink / raw)
To: rostedt
Cc: mhiramat, mark.rutland, mathieu.desnoyers, linux-kernel,
linux-trace-kernel, Wesley Atwell
Bootconfig expands arrays into repeated param=value entries, and the
kernel command line can repeat the same tracing parameter as well.
Several tracing __setup() handlers still overwrite their boot buffers,
so only the last ftrace filter, graph filter, trace option, kprobe
event, or trace trigger entry survives boot.
Preserve repeated values in the format their existing parsers already
consume: comma-delimited lists for ftrace filters and trace options,
semicolon-delimited lists for kprobe events, and per-chunk parsing for
trace_trigger=. The trace_trigger parser tokenizes its storage in
place, so keep a running length and only parse the newly appended
chunk into bootup_triggers[].
Fixes: 2af15d6a44b8 ("ftrace: add kernel command line function filtering")
Fixes: 7bcfaf54f591 ("tracing: Add trace_options kernel command line parameter")
Fixes: a01fdc897fa5 ("tracing: Add trace_trigger kernel command line option")
Fixes: 970988e19eb0 ("tracing/kprobe: Add kprobe_event= boot parameter")
Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
---
v2:
- No changes
kernel/trace/ftrace.c | 29 +++++++++++++++++++++++++----
kernel/trace/trace.c | 23 ++++++++++++++++++++++-
kernel/trace/trace_events.c | 23 ++++++++++++++++++++---
kernel/trace/trace_kprobe.c | 23 ++++++++++++++++++++++-
4 files changed, 89 insertions(+), 9 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8df69e702706..cdd46f639333 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6835,13 +6835,34 @@ EXPORT_SYMBOL_GPL(ftrace_set_global_notrace);
static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
+static void __init append_ftrace_boot_param(char *buf, const char *str,
+ char sep)
+{
+ size_t len, str_len;
+
+ if (buf[0] == '\0') {
+ strscpy(buf, str, FTRACE_FILTER_SIZE);
+ return;
+ }
+
+ len = strlen(buf);
+ str_len = strlen(str);
+ if (!str_len)
+ return;
+ if (str_len >= FTRACE_FILTER_SIZE - len - 1)
+ return;
+
+ buf[len] = sep;
+ strscpy(buf + len + 1, str, FTRACE_FILTER_SIZE - len - 1);
+}
+
/* Used by function selftest to not test if filter is set */
bool ftrace_filter_param __initdata;
static int __init set_ftrace_notrace(char *str)
{
ftrace_filter_param = true;
- strscpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
+ append_ftrace_boot_param(ftrace_notrace_buf, str, ',');
return 1;
}
__setup("ftrace_notrace=", set_ftrace_notrace);
@@ -6849,7 +6870,7 @@ __setup("ftrace_notrace=", set_ftrace_notrace);
static int __init set_ftrace_filter(char *str)
{
ftrace_filter_param = true;
- strscpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
+ append_ftrace_boot_param(ftrace_filter_buf, str, ',');
return 1;
}
__setup("ftrace_filter=", set_ftrace_filter);
@@ -6861,14 +6882,14 @@ static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
static int __init set_graph_function(char *str)
{
- strscpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+ append_ftrace_boot_param(ftrace_graph_buf, str, ',');
return 1;
}
__setup("ftrace_graph_filter=", set_graph_function);
static int __init set_graph_notrace_function(char *str)
{
- strscpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
+ append_ftrace_boot_param(ftrace_graph_notrace_buf, str, ',');
return 1;
}
__setup("ftrace_graph_notrace=", set_graph_notrace_function);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ebd996f8710e..42d03d36ae39 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -327,9 +327,30 @@ __setup("trace_instance=", boot_instance);
static char trace_boot_options_buf[MAX_TRACER_SIZE] __initdata;
+static void __init append_trace_boot_options(const char *str)
+{
+ size_t len, str_len;
+
+ if (trace_boot_options_buf[0] == '\0') {
+ strscpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
+ return;
+ }
+
+ len = strlen(trace_boot_options_buf);
+ str_len = strlen(str);
+ if (!str_len)
+ return;
+ if (str_len >= MAX_TRACER_SIZE - len - 1)
+ return;
+
+ trace_boot_options_buf[len] = ',';
+ strscpy(trace_boot_options_buf + len + 1, str,
+ MAX_TRACER_SIZE - len - 1);
+}
+
static int __init set_trace_boot_options(char *str)
{
- strscpy(trace_boot_options_buf, str, MAX_TRACER_SIZE);
+ append_trace_boot_options(str);
return 1;
}
__setup("trace_options=", set_trace_boot_options);
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 249d1cba72c0..c3981f62e4bc 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3679,20 +3679,37 @@ static struct boot_triggers {
} bootup_triggers[MAX_BOOT_TRIGGERS];
static char bootup_trigger_buf[COMMAND_LINE_SIZE];
+static int bootup_trigger_buf_len;
static int nr_boot_triggers;
static __init int setup_trace_triggers(char *str)
{
char *trigger;
char *buf;
+ ssize_t copied;
int i;
+ int start;
- strscpy(bootup_trigger_buf, str, COMMAND_LINE_SIZE);
+ if (bootup_trigger_buf_len >= COMMAND_LINE_SIZE)
+ return 1;
+
+ start = bootup_trigger_buf_len;
+ if (start && !*str)
+ return 1;
+
+ copied = strscpy(bootup_trigger_buf + start, str,
+ COMMAND_LINE_SIZE - start);
+ if (copied < 0) {
+ if (start)
+ return 1;
+ copied = strlen(bootup_trigger_buf + start);
+ }
+ bootup_trigger_buf_len += copied + 1;
trace_set_ring_buffer_expanded(NULL);
disable_tracing_selftest("running event triggers");
- buf = bootup_trigger_buf;
- for (i = 0; i < MAX_BOOT_TRIGGERS; i++) {
+ buf = bootup_trigger_buf + start;
+ for (i = nr_boot_triggers; i < MAX_BOOT_TRIGGERS; i++) {
trigger = strsep(&buf, ",");
if (!trigger)
break;
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index a5dbb72528e0..a63a56b55570 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -29,9 +29,30 @@
/* Kprobe early definition from command line */
static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
+static void __init append_kprobe_boot_event(const char *str)
+{
+ size_t len, str_len;
+
+ if (kprobe_boot_events_buf[0] == '\0') {
+ strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+ return;
+ }
+
+ len = strlen(kprobe_boot_events_buf);
+ str_len = strlen(str);
+ if (!str_len)
+ return;
+ if (str_len >= COMMAND_LINE_SIZE - len - 1)
+ return;
+
+ kprobe_boot_events_buf[len] = ';';
+ strscpy(kprobe_boot_events_buf + len + 1, str,
+ COMMAND_LINE_SIZE - len - 1);
+}
+
static int __init set_kprobe_boot_events(char *str)
{
- strscpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+ append_kprobe_boot_event(str);
disable_tracing_selftest("running kprobe events");
return 1;
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH v2 2/2] tracing: drain deferred trigger frees if kthread startup fails
2026-03-09 21:27 [PATCH v2 0/2] tracing: preserve repeated boot-time parameters and drain deferred trigger frees Wesley Atwell
2026-03-09 21:27 ` [PATCH v2 1/2] tracing: preserve repeated boot-time tracing parameters Wesley Atwell
@ 2026-03-09 21:27 ` Wesley Atwell
1 sibling, 0 replies; 3+ messages in thread
From: Wesley Atwell @ 2026-03-09 21:27 UTC (permalink / raw)
To: rostedt
Cc: mhiramat, mark.rutland, mathieu.desnoyers, linux-kernel,
linux-trace-kernel, Wesley Atwell
Boot-time trigger registration can fail before the trigger-data cleanup
kthread exists. Deferring those frees until late init is fine, but the
post-boot fallback must still drain the deferred list if kthread
creation never succeeds.
Otherwise, boot-deferred nodes can accumulate on
trigger_data_free_list, later frees fall back to synchronously freeing
only the current object, and the older queued entries are leaked
forever.
Keep the deferred boot-time behavior, but when kthread creation fails,
drain the whole queued list synchronously. Do the same in the late-init
drain path so queued entries are not stranded there either.
Fixes: 61d445af0a7c ("tracing: Add bulk garbage collection of freeing event_trigger_data")
Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
---
v2:
- Restore the dropped mutex recheck comment
- Clarify the synchronous fallback drain path
kernel/trace/trace_events_trigger.c | 79 ++++++++++++++++++++++++-----
1 file changed, 66 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index d5230b759a2d..428b46272ac8 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -22,6 +22,39 @@ static struct task_struct *trigger_kthread;
static struct llist_head trigger_data_free_list;
static DEFINE_MUTEX(trigger_data_kthread_mutex);
+static int trigger_kthread_fn(void *ignore);
+
+static void trigger_start_kthread_locked(void)
+{
+ lockdep_assert_held(&trigger_data_kthread_mutex);
+
+ if (!trigger_kthread) {
+ struct task_struct *kthread;
+
+ kthread = kthread_create(trigger_kthread_fn, NULL,
+ "trigger_data_free");
+ if (!IS_ERR(kthread))
+ WRITE_ONCE(trigger_kthread, kthread);
+ }
+}
+
+static void trigger_data_free_queued_locked(void)
+{
+ struct event_trigger_data *data, *tmp;
+ struct llist_node *llnodes;
+
+ lockdep_assert_held(&trigger_data_kthread_mutex);
+
+ llnodes = llist_del_all(&trigger_data_free_list);
+ if (!llnodes)
+ return;
+
+ tracepoint_synchronize_unregister();
+
+ llist_for_each_entry_safe(data, tmp, llnodes, llist)
+ kfree(data);
+}
+
/* Bulk garbage collection of event_trigger_data elements */
static int trigger_kthread_fn(void *ignore)
{
@@ -56,30 +89,50 @@ void trigger_data_free(struct event_trigger_data *data)
if (data->cmd_ops->set_filter)
data->cmd_ops->set_filter(NULL, data, NULL);
+ /*
+ * Boot-time trigger registration can fail before kthread creation
+ * works. Keep the deferred-free semantics during boot and let late
+ * init start the kthread to drain the list.
+ */
+ if (system_state == SYSTEM_BOOTING && !trigger_kthread) {
+ llist_add(&data->llist, &trigger_data_free_list);
+ return;
+ }
+
if (unlikely(!trigger_kthread)) {
guard(mutex)(&trigger_data_kthread_mutex);
+
+ trigger_start_kthread_locked();
/* Check again after taking mutex */
if (!trigger_kthread) {
- struct task_struct *kthread;
-
- kthread = kthread_create(trigger_kthread_fn, NULL,
- "trigger_data_free");
- if (!IS_ERR(kthread))
- WRITE_ONCE(trigger_kthread, kthread);
+ llist_add(&data->llist, &trigger_data_free_list);
+ /* Drain the queued frees synchronously if startup failed. */
+ trigger_data_free_queued_locked();
+ return;
}
}
- if (!trigger_kthread) {
- /* Do it the slow way */
- tracepoint_synchronize_unregister();
- kfree(data);
- return;
- }
-
llist_add(&data->llist, &trigger_data_free_list);
wake_up_process(trigger_kthread);
}
+static int __init trigger_data_free_init(void)
+{
+ guard(mutex)(&trigger_data_kthread_mutex);
+
+ if (llist_empty(&trigger_data_free_list))
+ return 0;
+
+ trigger_start_kthread_locked();
+ if (trigger_kthread)
+ wake_up_process(trigger_kthread);
+ else
+ trigger_data_free_queued_locked();
+
+ return 0;
+}
+late_initcall(trigger_data_free_init);
+
static inline void data_ops_trigger(struct event_trigger_data *data,
struct trace_buffer *buffer, void *rec,
struct ring_buffer_event *event)
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread