* [PATCH 1/2] tracing: Embed 'char comm[16]' in a structure
2026-06-26 21:23 [PATCH rfc 0/2] Improvements to ftrace comm[] handling David Laight
@ 2026-06-26 21:23 ` David Laight
2026-06-26 21:23 ` [PATCH 2/2] tracing: Keep pid and comm[] in the same structure David Laight
1 sibling, 0 replies; 3+ messages in thread
From: David Laight @ 2026-06-26 21:23 UTC (permalink / raw)
To: Steven Rostedt, Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, Michal Koutný
Cc: David Laight
Embedding the array in a stucture makes the size explicit and lets
structure copies be used.
Limit the size to 16 charatacters even if task_struct.comm is
made larger (there are plans to increase it).
Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
kernel/trace/blktrace.c | 28 +++++++++----------
kernel/trace/trace.c | 3 +-
kernel/trace/trace.h | 9 ++++--
kernel/trace/trace_events_filter.c | 2 +-
kernel/trace/trace_events_hist.c | 26 +++++++----------
kernel/trace/trace_functions_graph.c | 10 +++----
kernel/trace/trace_output.c | 24 ++++++++--------
kernel/trace/trace_sched_switch.c | 42 ++++++++++++++++------------
8 files changed, 75 insertions(+), 69 deletions(-)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 8cd2520b4c99..68ffc95548b7 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1590,20 +1590,20 @@ static void blk_log_dump_pdu(struct trace_seq *s,
static void blk_log_generic(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
{
- char cmd[TASK_COMM_LEN];
+ struct trace_comm cmd;
- trace_find_cmdline(ent->pid, cmd);
+ trace_find_cmdline(ent->pid, &cmd);
if (t_action(ent) & BLK_TC_ACT(BLK_TC_PC)) {
trace_seq_printf(s, "%u ", t_bytes(ent));
blk_log_dump_pdu(s, ent, has_cg);
- trace_seq_printf(s, "[%s]\n", cmd);
+ trace_seq_printf(s, "[%s]\n", cmd.comm);
} else {
if (t_sec(ent))
trace_seq_printf(s, "%llu + %u [%s]\n",
- t_sector(ent), t_sec(ent), cmd);
+ t_sector(ent), t_sec(ent), cmd.comm);
else
- trace_seq_printf(s, "[%s]\n", cmd);
+ trace_seq_printf(s, "[%s]\n", cmd.comm);
}
}
@@ -1637,30 +1637,30 @@ static void blk_log_remap(struct trace_seq *s, const struct trace_entry *ent, bo
static void blk_log_plug(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
{
- char cmd[TASK_COMM_LEN];
+ struct trace_comm cmd;
- trace_find_cmdline(ent->pid, cmd);
+ trace_find_cmdline(ent->pid, &cmd);
- trace_seq_printf(s, "[%s]\n", cmd);
+ trace_seq_printf(s, "[%s]\n", cmd.comm);
}
static void blk_log_unplug(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
{
- char cmd[TASK_COMM_LEN];
+ struct trace_comm cmd;
- trace_find_cmdline(ent->pid, cmd);
+ trace_find_cmdline(ent->pid, &cmd);
- trace_seq_printf(s, "[%s] %llu\n", cmd, get_pdu_int(ent, has_cg));
+ trace_seq_printf(s, "[%s] %llu\n", cmd.comm, get_pdu_int(ent, has_cg));
}
static void blk_log_split(struct trace_seq *s, const struct trace_entry *ent, bool has_cg)
{
- char cmd[TASK_COMM_LEN];
+ struct trace_comm cmd;
- trace_find_cmdline(ent->pid, cmd);
+ trace_find_cmdline(ent->pid, &cmd);
trace_seq_printf(s, "%llu / %llu [%s]\n", t_sector(ent),
- get_pdu_int(ent, has_cg), cmd);
+ get_pdu_int(ent, has_cg), cmd.comm);
}
static void blk_log_msg(struct trace_seq *s, const struct trace_entry *ent,
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6eb4d3097a4d..7de658b8ee0d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -52,6 +52,7 @@
#include <linux/sort.h>
#include <linux/io.h> /* vmap_page_range() */
#include <linux/fs_context.h>
+#include <linux/trace_printk.h>
#include <asm/setup.h> /* COMMAND_LINE_SIZE */
@@ -2972,7 +2973,7 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
seq_puts(m, "# -----------------\n");
seq_printf(m, "# | task: %.16s-%d "
"(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
- data->comm, data->pid,
+ data->comm.comm, data->pid,
from_kuid_munged(seq_user_ns(m), data->uid), data->nice,
data->policy, data->rt_priority);
seq_puts(m, "# -----------------\n");
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 80fe152af1dd..afd59d79e1fe 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -183,6 +183,11 @@ struct fexit_trace_entry_head {
struct trace_array;
+/* task_struct->comm[] may be truncated to save memory/width */
+struct trace_comm {
+ char comm[16];
+};
+
/*
* The CPU trace array - it consists of thousands of trace entries
* plus some other descriptor data: (for example which task started
@@ -203,7 +208,7 @@ struct trace_array_cpu {
u64 preempt_timestamp;
pid_t pid;
kuid_t uid;
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
#ifdef CONFIG_FUNCTION_TRACER
int ftrace_ignore_pid;
@@ -906,7 +911,7 @@ void trace_last_func_repeats(struct trace_array *tr,
extern u64 ftrace_now(int cpu);
-extern void trace_find_cmdline(int pid, char comm[]);
+extern void trace_find_cmdline(int pid, struct trace_comm *comm);
extern int trace_find_tgid(int pid);
extern void trace_event_follow_fork(struct trace_array *tr, bool enable);
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 609325f57942..749887aff315 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -994,7 +994,7 @@ static int filter_pred_comm(struct filter_pred *pred, void *event)
int cmp;
cmp = pred->regex->match(current->comm, pred->regex,
- TASK_COMM_LEN);
+ sizeof(current->comm));
return cmp ^ pred->not;
}
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 0dbbf6cca9bc..1b51491b2a41 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -680,7 +680,7 @@ struct track_data {
};
struct hist_elt_data {
- char *comm;
+ struct trace_comm *comm;
u64 *var_ref_vals;
char **field_var_str;
int n_field_var_str;
@@ -756,7 +756,7 @@ static struct track_data *track_data_alloc(unsigned int key_len,
data->elt.private_data = elt_data;
- elt_data->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
+ elt_data->comm = kzalloc_obj(*elt_data->comm);
if (!elt_data->comm) {
track_data_free(data);
return ERR_PTR(-ENOMEM);
@@ -1608,19 +1608,19 @@ parse_hist_trigger_attrs(struct trace_array *tr, char *trigger_str)
return ERR_PTR(ret);
}
-static inline void save_comm(char *comm, struct task_struct *task)
+static inline void save_comm(struct trace_comm *comm, struct task_struct *task)
{
if (!task->pid) {
- strcpy(comm, "<idle>");
+ strcpy(comm->comm, "<idle>");
return;
}
if (WARN_ON_ONCE(task->pid < 0)) {
- strcpy(comm, "<XXX>");
+ strcpy(comm->comm, "<XXX>");
return;
}
- strscpy(comm, task->comm, TASK_COMM_LEN);
+ strscpy(comm->comm, task->comm);
}
static void hist_elt_data_free(struct hist_elt_data *elt_data)
@@ -1646,7 +1646,6 @@ static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
{
struct hist_trigger_data *hist_data = elt->map->private_data;
- unsigned int size = TASK_COMM_LEN;
struct hist_elt_data *elt_data;
struct hist_field *hist_field;
unsigned int i, n_str;
@@ -1659,7 +1658,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
hist_field = hist_data->fields[i];
if (hist_field->flags & HIST_FIELD_FL_EXECNAME) {
- elt_data->comm = kzalloc(size, GFP_KERNEL);
+ elt_data->comm = kzalloc_obj(*elt_data->comm);
if (!elt_data->comm) {
kfree(elt_data);
return -ENOMEM;
@@ -1677,8 +1676,6 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
BUILD_BUG_ON(STR_VAR_LEN_MAX & (sizeof(u64) - 1));
- size = STR_VAR_LEN_MAX;
-
elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL);
if (!elt_data->field_var_str) {
hist_elt_data_free(elt_data);
@@ -1687,7 +1684,7 @@ static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
elt_data->n_field_var_str = n_str;
for (i = 0; i < n_str; i++) {
- elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
+ elt_data->field_var_str[i] = kzalloc(STR_VAR_LEN_MAX, GFP_KERNEL);
if (!elt_data->field_var_str[i]) {
hist_elt_data_free(elt_data);
return -ENOMEM;
@@ -3449,7 +3446,7 @@ static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
elt_data = context->elt->private_data;
track_elt_data = track_data->elt.private_data;
if (elt_data->comm)
- strscpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
+ track_elt_data->comm = elt_data->comm;
track_data->updated = true;
@@ -5505,16 +5502,13 @@ static void hist_trigger_print_key(struct seq_file *m,
uval, (void *)(uintptr_t)uval);
} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
struct hist_elt_data *elt_data = elt->private_data;
- char *comm;
if (WARN_ON_ONCE(!elt_data))
return;
- comm = elt_data->comm;
-
uval = *(u64 *)(key + key_field->offset);
seq_printf(m, "%s: %-16s[%10llu]", field_name,
- comm, uval);
+ elt_data->comm->comm, uval);
} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
const char *syscall_name;
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 0d2d3a2ea7dd..e46c5aa0d4e4 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -561,19 +561,19 @@ static void print_graph_cpu(struct trace_seq *s, int cpu)
static void print_graph_proc(struct trace_seq *s, pid_t pid)
{
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
/* sign + log10(MAX_INT) + '\0' */
char pid_str[12];
int spaces = 0;
int len;
int i;
- trace_find_cmdline(pid, comm);
- comm[7] = '\0';
+ trace_find_cmdline(pid, &comm);
+ comm.comm[7] = '\0';
sprintf(pid_str, "%d", pid);
/* 1 stands for the "-" character */
- len = strlen(comm) + strlen(pid_str) + 1;
+ len = strlen(comm.comm) + strlen(pid_str) + 1;
if (len < TRACE_GRAPH_PROCINFO_LENGTH)
spaces = TRACE_GRAPH_PROCINFO_LENGTH - len;
@@ -582,7 +582,7 @@ static void print_graph_proc(struct trace_seq *s, pid_t pid)
for (i = 0; i < spaces / 2; i++)
trace_seq_putc(s, ' ');
- trace_seq_printf(s, "%s-%s", comm, pid_str);
+ trace_seq_printf(s, "%s-%s", comm.comm, pid_str);
/* Last spaces to align center */
for (i = 0; i < spaces - (spaces / 2); i++)
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index a5ad76175d10..58405291b44f 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -554,12 +554,12 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
static int
lat_print_generic(struct trace_seq *s, struct trace_entry *entry, int cpu)
{
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
- trace_find_cmdline(entry->pid, comm);
+ trace_find_cmdline(entry->pid, &comm);
trace_seq_printf(s, "%8.8s-%-7d %3d",
- comm, entry->pid, cpu);
+ comm.comm, entry->pid, cpu);
return trace_print_lat_fmt(s, entry);
}
@@ -658,11 +658,11 @@ int trace_print_context(struct trace_iterator *iter)
struct trace_array *tr = iter->tr;
struct trace_seq *s = &iter->seq;
struct trace_entry *entry = iter->ent;
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
- trace_find_cmdline(entry->pid, comm);
+ trace_find_cmdline(entry->pid, &comm);
- trace_seq_printf(s, "%16s-%-7d ", comm, entry->pid);
+ trace_seq_printf(s, "%16s-%-7d ", comm.comm, entry->pid);
if (tr->trace_flags & TRACE_ITER(RECORD_TGID)) {
unsigned int tgid = trace_find_tgid(entry->pid);
@@ -700,13 +700,13 @@ int trace_print_lat_context(struct trace_iterator *iter)
entry = iter->ent;
if (verbose) {
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
- trace_find_cmdline(entry->pid, comm);
+ trace_find_cmdline(entry->pid, &comm);
trace_seq_printf(
s, "%16s %7d %3d %d %08x %08lx ",
- comm, entry->pid, iter->cpu, entry->flags,
+ comm.comm, entry->pid, iter->cpu, entry->flags,
entry->preempt_count & 0xf, iter->idx);
} else {
lat_print_generic(s, entry, iter->cpu);
@@ -1276,7 +1276,7 @@ static enum print_line_t trace_ctxwake_print(struct trace_iterator *iter,
char *delim)
{
struct ctx_switch_entry *field;
- char comm[TASK_COMM_LEN];
+ struct trace_comm comm;
int S, T;
@@ -1284,7 +1284,7 @@ static enum print_line_t trace_ctxwake_print(struct trace_iterator *iter,
T = task_index_to_char(field->next_state);
S = task_index_to_char(field->prev_state);
- trace_find_cmdline(field->next_pid, comm);
+ trace_find_cmdline(field->next_pid, &comm);
trace_seq_printf(&iter->seq,
" %7d:%3d:%c %s [%03d] %7d:%3d:%c %s\n",
field->prev_pid,
@@ -1293,7 +1293,7 @@ static enum print_line_t trace_ctxwake_print(struct trace_iterator *iter,
field->next_cpu,
field->next_pid,
field->next_prio,
- T, comm);
+ T, comm.comm);
return trace_handle_return(&iter->seq);
}
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index e9f0ff962660..972883643097 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -172,27 +172,33 @@ struct saved_cmdlines_buffer {
unsigned *map_cmdline_to_pid;
unsigned cmdline_num;
int cmdline_idx;
- char saved_cmdlines[];
+ struct trace_comm saved_cmdlines[];
};
static struct saved_cmdlines_buffer *savedcmd;
/* Holds the size of a cmdline and pid element */
#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
- (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
+ (sizeof(struct trace_comm) + sizeof((s)->map_cmdline_to_pid[0]))
-static inline char *get_saved_cmdlines(int idx)
+static inline struct trace_comm *get_saved_cmdlines(int idx)
{
- return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
+ return &savedcmd->saved_cmdlines[idx];
}
-static inline void set_cmdline(int idx, const char *cmdline)
+static inline void set_cmdline(int idx, const struct task_struct *tsk)
{
- strscpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
+ struct trace_comm *comm = get_saved_cmdlines(idx);
+
+ BUILD_BUG_ON(sizeof(comm->comm) > sizeof(tsk->comm));
+
+ memcpy(comm->comm, tsk->comm, sizeof comm->comm);
+ if (sizeof(comm->comm) != sizeof(tsk->comm))
+ comm->comm[ARRAY_SIZE(comm->comm) - 1] = 0;
}
static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
{
- int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
+ int order = get_order(sizeof(*s) + s->cmdline_num * sizeof(struct trace_comm));
kmemleak_free(s);
free_pages((unsigned long)s, order);
@@ -222,7 +228,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
s->cmdline_num = val;
/* Place map_cmdline_to_pid array right after saved_cmdlines */
- s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
+ s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val];
memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
sizeof(s->map_pid_to_cmdline));
@@ -273,25 +279,25 @@ int trace_save_cmdline(struct task_struct *tsk)
}
savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
- set_cmdline(idx, tsk->comm);
+ set_cmdline(idx, tsk);
arch_spin_unlock(&trace_cmdline_lock);
return 1;
}
-static void __trace_find_cmdline(int pid, char comm[])
+static void __trace_find_cmdline(int pid, struct trace_comm *comm)
{
unsigned map;
int tpid;
if (!pid) {
- strcpy(comm, "<idle>");
+ strcpy(comm->comm, "<idle>");
return;
}
if (WARN_ON_ONCE(pid < 0)) {
- strcpy(comm, "<XXX>");
+ strcpy(comm->comm, "<XXX>");
return;
}
@@ -300,14 +306,14 @@ static void __trace_find_cmdline(int pid, char comm[])
if (map != NO_CMDLINE_MAP) {
tpid = savedcmd->map_cmdline_to_pid[map];
if (tpid == pid) {
- strscpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
+ *comm = *get_saved_cmdlines(map);
return;
}
}
- strcpy(comm, "<...>");
+ strcpy(comm->comm, "<...>");
}
-void trace_find_cmdline(int pid, char comm[])
+void trace_find_cmdline(int pid, struct trace_comm *comm)
{
preempt_disable();
arch_spin_lock(&trace_cmdline_lock);
@@ -561,11 +567,11 @@ static void saved_cmdlines_stop(struct seq_file *m, void *v)
static int saved_cmdlines_show(struct seq_file *m, void *v)
{
- char buf[TASK_COMM_LEN];
+ struct trace_comm buf;
unsigned int *pid = v;
- __trace_find_cmdline(*pid, buf);
- seq_printf(m, "%d %s\n", *pid, buf);
+ __trace_find_cmdline(*pid, &buf);
+ seq_printf(m, "%d %s\n", *pid, buf.comm);
return 0;
}
--
2.39.5
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH 2/2] tracing: Keep pid and comm[] in the same structure
2026-06-26 21:23 [PATCH rfc 0/2] Improvements to ftrace comm[] handling David Laight
2026-06-26 21:23 ` [PATCH 1/2] tracing: Embed 'char comm[16]' in a structure David Laight
@ 2026-06-26 21:23 ` David Laight
1 sibling, 0 replies; 3+ messages in thread
From: David Laight @ 2026-06-26 21:23 UTC (permalink / raw)
To: Steven Rostedt, Masami Hiramatsu, Mathieu Desnoyers, linux-kernel,
linux-trace-kernel, Michal Koutný
Cc: David Laight
Rather than have two separate dynamic arrays on the end of struct
saved_commandlines_buffer have a single dynamic array where each
entry contains the pid and associated task->comm[].
This simplifies the initialisation and lookup.
Don't bother trying to initialise the pid field no a non-zero value,
it only matters in the tracing_saved_cmdlines_seq_ops code.
Allocate entry [0] first so that the tracing_saved_cmdlines_seq_ops
code can just index the array with the file offset.
The code now uses the correct size when determining the page 'order'
to free the structure. The smaller size will always give the same
'order'.
Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
Is there any reason why this code uses alloc_pages() rather
than vmalloc()?
map_pid_to_cmdline[] is 64k*sizeof(int) so the whole structure
expands to 512k with about 64k/20 (about 3200) pid entries even
though the default is 128.
AFAICT there is only one copy of the data - so it could be static.
Perhaps with pointers to map_pid_cmdline[] and (after this patch)
pid_comm[], both of which could be separately resized.
I also noticed that map_pid_to_cmdline[] contains indexes into
pid_comm[], restricting these to 16bits would half the data area.
kernel/trace/trace_sched_switch.c | 97 +++++++++++++------------------
1 file changed, 39 insertions(+), 58 deletions(-)
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index 972883643097..5e7c8cf444b8 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -167,27 +167,21 @@ static size_t tgid_map_max;
* where interrupt is disabled.
*/
static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+struct pid_comm {
+ pid_t pid;
+ struct trace_comm comm;
+};
struct saved_cmdlines_buffer {
unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
- unsigned *map_cmdline_to_pid;
unsigned cmdline_num;
int cmdline_idx;
- struct trace_comm saved_cmdlines[];
+ struct pid_comm pid_comm[];
};
static struct saved_cmdlines_buffer *savedcmd;
-/* Holds the size of a cmdline and pid element */
-#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
- (sizeof(struct trace_comm) + sizeof((s)->map_cmdline_to_pid[0]))
-
-static inline struct trace_comm *get_saved_cmdlines(int idx)
-{
- return &savedcmd->saved_cmdlines[idx];
-}
-
-static inline void set_cmdline(int idx, const struct task_struct *tsk)
+static inline void set_cmdline(struct pid_comm *pid_comm, const struct task_struct *tsk)
{
- struct trace_comm *comm = get_saved_cmdlines(idx);
+ struct trace_comm *comm = &pid_comm->comm;
BUILD_BUG_ON(sizeof(comm->comm) > sizeof(tsk->comm));
@@ -212,7 +206,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
int order;
/* Figure out how much is needed to hold the given number of cmdlines */
- orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
+ orig_size = sizeof(*s) + val * sizeof(s->pid_comm[0]);
order = get_order(orig_size);
size = 1 << (order + PAGE_SHIFT);
page = alloc_pages(GFP_KERNEL, order);
@@ -224,16 +218,11 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
memset(s, 0, sizeof(*s));
/* Round up to actual allocation */
- val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
+ val = (size - sizeof(*s)) / sizeof(s->pid_comm[0]);
s->cmdline_num = val;
- /* Place map_cmdline_to_pid array right after saved_cmdlines */
- s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val];
-
memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
sizeof(s->map_pid_to_cmdline));
- memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
- val * sizeof(*s->map_cmdline_to_pid));
return s;
}
@@ -247,6 +236,7 @@ int trace_create_savedcmd(void)
int trace_save_cmdline(struct task_struct *tsk)
{
+ struct pid_comm *pid_comm;
unsigned tpid, idx;
/* treat recording of idle task as a success */
@@ -272,14 +262,16 @@ int trace_save_cmdline(struct task_struct *tsk)
idx = savedcmd->map_pid_to_cmdline[tpid];
if (idx == NO_CMDLINE_MAP) {
- idx = (savedcmd->cmdline_idx + 1) % savedcmd->cmdline_num;
-
+ idx = savedcmd->cmdline_idx;
savedcmd->map_pid_to_cmdline[tpid] = idx;
+ if (++idx >= savedcmd->cmdline_num)
+ idx = 0;
savedcmd->cmdline_idx = idx;
}
- savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
- set_cmdline(idx, tsk);
+ pid_comm = savedcmd->pid_comm + idx;
+ pid_comm->pid = tsk->pid;
+ set_cmdline(pid_comm, tsk);
arch_spin_unlock(&trace_cmdline_lock);
@@ -288,8 +280,8 @@ int trace_save_cmdline(struct task_struct *tsk)
static void __trace_find_cmdline(int pid, struct trace_comm *comm)
{
+ struct pid_comm *pid_comm;
unsigned map;
- int tpid;
if (!pid) {
strcpy(comm->comm, "<idle>");
@@ -301,12 +293,11 @@ static void __trace_find_cmdline(int pid, struct trace_comm *comm)
return;
}
- tpid = pid & (PID_MAX_DEFAULT - 1);
- map = savedcmd->map_pid_to_cmdline[tpid];
+ map = savedcmd->map_pid_to_cmdline[pid & (PID_MAX_DEFAULT - 1)];
if (map != NO_CMDLINE_MAP) {
- tpid = savedcmd->map_cmdline_to_pid[map];
- if (tpid == pid) {
- *comm = *get_saved_cmdlines(map);
+ pid_comm = savedcmd->pid_comm + map;
+ if (pid_comm->pid == pid) {
+ *comm = pid_comm->comm;;
return;
}
}
@@ -521,42 +512,34 @@ const struct file_operations tracing_saved_tgids_fops = {
.release = seq_release,
};
-static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
+static struct pid_comm *saved_cmdlines_entry(loff_t off)
{
- unsigned int *ptr = v;
+ struct pid_comm *pid_comm;
- if (*pos || m->count)
- ptr++;
-
- (*pos)++;
+ if (off >= savedcmd->cmdline_num)
+ return NULL;
- for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
- ptr++) {
- if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
- continue;
+ /* Entries are used in sequence and never freed */
+ pid_comm = &savedcmd->pid_comm[off];
+ return pid_comm->pid ? pid_comm : NULL;
+}
- return ptr;
- }
+static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ loff_t off = *pos;
- return NULL;
+ v = saved_cmdlines_entry(off);
+ if (v)
+ *pos = off + 1;
+ return v;
}
static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
{
- void *v;
- loff_t l = 0;
-
preempt_disable();
arch_spin_lock(&trace_cmdline_lock);
- v = &savedcmd->map_cmdline_to_pid[0];
- while (l <= *pos) {
- v = saved_cmdlines_next(m, v, &l);
- if (!v)
- return NULL;
- }
-
- return v;
+ return saved_cmdlines_entry(*pos);
}
static void saved_cmdlines_stop(struct seq_file *m, void *v)
@@ -567,11 +550,9 @@ static void saved_cmdlines_stop(struct seq_file *m, void *v)
static int saved_cmdlines_show(struct seq_file *m, void *v)
{
- struct trace_comm buf;
- unsigned int *pid = v;
+ struct pid_comm *ptr = v;
- __trace_find_cmdline(*pid, &buf);
- seq_printf(m, "%d %s\n", *pid, buf.comm);
+ seq_printf(m, "%d %s\n", ptr->pid, ptr->comm.comm);
return 0;
}
--
2.39.5
^ permalink raw reply related [flat|nested] 3+ messages in thread