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Message-ID: <20250520093726.2009696-1-tmricht@linux.ibm.com>
Date: Tue, 20 May 2025 11:37:26 +0200
From: Thomas Richter <tmricht@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
linux-perf-users@...r.kernel.org, acme@...nel.org, namhyung@...nel.org
Cc: agordeev@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
hca@...ux.ibm.com, Thomas Richter <tmricht@...ux.ibm.com>,
Alexander Egorenkov <egorenar@...ux.ibm.com>
Subject: [PATCH V3] perf ftrace: Use process/session specific trace settings
V2 --> V3: Use Arnaldo's proposal for the commit message.
Add Namhyung's review comments.
V1 --> V2: Add Suggestion from Arnaldo Cavalho de Melo confirmed by
Steven Rostedt. Use rmdir(../tracing/instances/dir) to stop
process/session specific tracing and delete all
process/session specific setings.
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.
Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
Suggested-by: Arnaldo Carvalho de Melo <acme@...nel.org>
Reported-by: Alexander Egorenkov <egorenar@...ux.ibm.com>
---
tools/perf/builtin-ftrace.c | 101 +++++++++++++++++++++++++++++++-----
1 file changed, 87 insertions(+), 14 deletions(-)
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 7caa18d5ffc3..bba36ebc2aa7 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -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;
}
--
2.49.0
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