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Message-ID: <20250519145235.56006-1-tmricht@linux.ibm.com>
Date: Mon, 19 May 2025 16:52:35 +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 v2] perf ftrace: Use process/session specific trace settings
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.
Fix this behavior and restore the trace setting to what
is was before the invocation of the command.
On Fedora 41 and 42 tracing is turned on by default.
This patch use 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.
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 | 105 +++++++++++++++++++++++++++++++-----
1 file changed, 91 insertions(+), 14 deletions(-)
diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 7caa18d5ffc3..3faf96e7185e 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -38,6 +38,8 @@
#include "util/units.h"
#include "util/parse-sublevel-options.h"
+#include <sys/stat.h>
+
#define DEFAULT_TRACER "function_graph"
static volatile sig_atomic_t workload_exec_errno;
@@ -45,6 +47,8 @@ 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 +104,34 @@ 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 a 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;
+
+ put_tracing_file(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 +141,7 @@ 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 +199,7 @@ 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 +241,7 @@ 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 +331,36 @@ 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)
+{
+ rmdir(tracing_instance);
+}
+
+/* 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)
+ return -1;
+ strcpy(tracing_instance, path);
+ put_tracing_file(path);
+ path = mkdtemp(tracing_instance);
+ if (!path) {
+ pr_err("failed to create tracing/instances directory\n");
+ return -1;
+ }
+ return 0;
+}
+
static int set_tracing_pid(struct perf_ftrace *ftrace)
{
int i;
@@ -629,14 +691,19 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace)
select_tracer(ftrace);
+ if (init_tracing_instance() < 0) {
+ pr_err("failed to create tracing/instances\n");
+ 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 +991,11 @@ 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) {
+ pr_err("failed to create tracing/instances\n");
+ return -1;
+ }
+
if (reset_tracing_files(ftrace) < 0) {
pr_err("failed to reset ftrace\n");
return -1;
@@ -942,7 +1014,7 @@ 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 +1065,7 @@ 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 +1376,22 @@ static int __cmd_profile(struct perf_ftrace *ftrace)
goto out;
}
+ if (init_tracing_instance() < 0) {
+ pr_err("failed to create tracing/instances\n");
+ 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 +1400,7 @@ 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 +1462,7 @@ 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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