Commit ba5f102e authored by Thomas Richter's avatar Thomas Richter Committed by Arnaldo Carvalho de Melo
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perf ftrace: Use process/session specific trace settings 



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: default avatarAlexander Egorenkov <egorenar@linux.ibm.com>
Suggested-by: default avatarArnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: default avatarThomas 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent e48b92f9

tools/perf/builtin-ftrace.c

+87 −14
Original line number Diff line number Diff line
@@ -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;

}