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perf ftrace: Use process/session specific trace settings

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Executing 'perf ftrace' commands 'ftrace', 'profile' and 'latency' leave
tracing disabled as can seen in this output:

 # echo 1 > /sys/kernel/debug/tracing/tracing_on
 # cat /sys/kernel/debug/tracing/tracing_on
 1
 # perf ftrace trace --graph-opts depth=5 sleep 0.1 > /dev/null
 # cat /sys/kernel/debug/tracing/tracing_on
 0
 #

The 'tracing_on' file is not restored to its value before the command.

To fix that this patch uses the .../tracing/instances/XXX subdirectory
feature.

Each 'perf ftrace' invocation creates its own session/process
specific subdirectory and does not change the global state
in the .../tracing directory itself.

Use rmdir(../tracing/instances/dir) to stop process/session specific
tracing and delete all process/session specific setings.

Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20250520093726.2009696-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Thomas Richter 2025-05-20 11:37:26 +02:00 committed by Arnaldo Carvalho de Melo
parent e48b92f9e1
commit ba5f102eec
1 changed files with 87 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

101
tools/perf/builtin-ftrace.c
View File

@ -19,6 +19,7 @@
#include <ctype.h>
#include <linux/capability.h>
#include <linux/string.h>
#include <sys/stat.h>
#include "debug.h"
#include <subcmd/pager.h>
@ -45,6 +46,8 @@ static volatile sig_atomic_t done;
static struct stats latency_stats; /* for tracepoints */
static char tracing_instance[PATH_MAX]; /* Trace instance directory */
static void sig_handler(int sig __maybe_unused)
{
done = true;
@ -100,6 +103,34 @@ static bool is_ftrace_supported(void)
return supported;
}
/*
* Wrapper to test if a file in directory .../tracing/instances/XXX
* exists. If so return the .../tracing/instances/XXX file for use.
* Otherwise the file exists only in directory .../tracing and
* is applicable to all instances, for example file available_filter_functions.
* Return that file name in this case.
*
* This functions works similar to get_tracing_file() and expects its caller
* to free the returned file name.
*
* The global variable tracing_instance is set in init_tracing_instance()
* called at the beginning to a process specific tracing subdirectory.
*/
static char *get_tracing_instance_file(const char *name)
{
char *file;
if (asprintf(&file, "%s/%s", tracing_instance, name) < 0)
return NULL;
if (!access(file, F_OK))
return file;
free(file);
file = get_tracing_file(name);
return file;
}
static int __write_tracing_file(const char *name, const char *val, bool append)
{
char *file;
@ -109,7 +140,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
char errbuf[512];
char *val_copy;
file = get_tracing_file(name);
file = get_tracing_instance_file(name);
if (!file) {
pr_debug("cannot get tracing file: %s\n", name);
return -1;
@ -167,7 +198,7 @@ static int read_tracing_file_to_stdout(const char *name)
int fd;
int ret = -1;
file = get_tracing_file(name);
file = get_tracing_instance_file(name);
if (!file) {
pr_debug("cannot get tracing file: %s\n", name);
return -1;
@ -209,7 +240,7 @@ static int read_tracing_file_by_line(const char *name,
char *file;
FILE *fp;
file = get_tracing_file(name);
file = get_tracing_instance_file(name);
if (!file) {
pr_debug("cannot get tracing file: %s\n", name);
return -1;
@ -299,6 +330,39 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
return 0;
}
/* Remove .../tracing/instances/XXX subdirectory created with
* init_tracing_instance().
*/
static void exit_tracing_instance(void)
{
if (rmdir(tracing_instance))
pr_err("failed to delete tracing/instances directory\n");
}
/* Create subdirectory within .../tracing/instances/XXX to have session
* or process specific setup. To delete this setup, simply remove the
* subdirectory.
*/
static int init_tracing_instance(void)
{
char dirname[] = "instances/perf-ftrace-XXXXXX";
char *path;
path = get_tracing_file(dirname);
if (!path)
goto error;
strncpy(tracing_instance, path, sizeof(tracing_instance) - 1);
put_tracing_file(path);
path = mkdtemp(tracing_instance);
if (!path)
goto error;
return 0;
error:
pr_err("failed to create tracing/instances directory\n");
return -1;
}
static int set_tracing_pid(struct perf_ftrace *ftrace)
{
int i;
@ -629,14 +693,17 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
select_tracer(ftrace);
if (init_tracing_instance() < 0)
goto out;
if (reset_tracing_files(ftrace) < 0) {
pr_err("failed to reset ftrace\n");
goto out;
goto out_reset;
}
/* reset ftrace buffer */
if (write_tracing_file("trace", "0") < 0)
goto out;
goto out_reset;
if (set_tracing_options(ftrace) < 0)
goto out_reset;
@ -648,7 +715,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
setup_pager();
trace_file = get_tracing_file("trace_pipe");
trace_file = get_tracing_instance_file("trace_pipe");
if (!trace_file) {
pr_err("failed to open trace_pipe\n");
goto out_reset;
@ -723,7 +790,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
out_close_fd:
close(trace_fd);
out_reset:
reset_tracing_files(ftrace);
exit_tracing_instance();
out:
return (done && !workload_exec_errno) ? 0 : -1;
}
@ -924,6 +991,9 @@ static int prepare_func_latency(struct perf_ftrace *ftrace)
if (ftrace->target.use_bpf)
return perf_ftrace__latency_prepare_bpf(ftrace);
if (init_tracing_instance() < 0)
return -1;
if (reset_tracing_files(ftrace) < 0) {
pr_err("failed to reset ftrace\n");
return -1;
@ -942,7 +1012,7 @@ static int prepare_func_latency(struct perf_ftrace *ftrace)
return -1;
}
trace_file = get_tracing_file("trace_pipe");
trace_file = get_tracing_instance_file("trace_pipe");
if (!trace_file) {
pr_err("failed to open trace_pipe\n");
return -1;
@ -993,7 +1063,7 @@ static int cleanup_func_latency(struct perf_ftrace *ftrace)
if (ftrace->target.use_bpf)
return perf_ftrace__latency_cleanup_bpf(ftrace);
reset_tracing_files(ftrace);
exit_tracing_instance();
return 0;
}
@ -1304,17 +1374,20 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
goto out;
}
if (init_tracing_instance() < 0)
goto out;
if (reset_tracing_files(ftrace) < 0) {
pr_err("failed to reset ftrace\n");
goto out;
goto out_reset;
}
/* reset ftrace buffer */
if (write_tracing_file("trace", "0") < 0)
goto out;
goto out_reset;
if (set_tracing_options(ftrace) < 0)
return -1;
goto out_reset;
if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
@ -1323,7 +1396,7 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
setup_pager();
trace_file = get_tracing_file("trace_pipe");
trace_file = get_tracing_instance_file("trace_pipe");
if (!trace_file) {
pr_err("failed to open trace_pipe\n");
goto out_reset;
@ -1385,7 +1458,7 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
out_close_fd:
close(trace_fd);
out_reset:
reset_tracing_files(ftrace);
exit_tracing_instance();
out:
return (done && !workload_exec_errno) ? 0 : -1;
}