This is a note to let you know that I've just added the patch titled
tracing: Remove unneeded synth_event_mutex
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-remove-unneeded-synth_event_mutex.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable+bounces-43481-greg=kroah.com@xxxxxxxxxxxxxxx Thu May 9 04:30:22 2024
From: George Guo <dongtai.guo@xxxxxxxxx>
Date: Thu, 9 May 2024 10:29:22 +0800
Subject: tracing: Remove unneeded synth_event_mutex
To: gregkh@xxxxxxxxxxxxxxxxxxx, rostedt@xxxxxxxxxxx, mhiramat@xxxxxxxxxx, tom.zanussi@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx, George Guo <guodongtai@xxxxxxxxxx>
Message-ID: <20240509022931.3513365-5-dongtai.guo@xxxxxxxxx>
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
commit 0e2b81f7b52a1c1a8c46986f9ca01eb7b3c421f8 upstream.
Rmove unneeded synth_event_mutex. This mutex protects the reference
count in synth_event, however, those operational points are already
protected by event_mutex.
1. In __create_synth_event() and create_or_delete_synth_event(),
those synth_event_mutex clearly obtained right after event_mutex.
2. event_hist_trigger_func() is trigger_hist_cmd.func() which is
called by trigger_process_regex(), which is a part of
event_trigger_regex_write() and this function takes event_mutex.
3. hist_unreg_all() is trigger_hist_cmd.unreg_all() which is called
by event_trigger_regex_open() and it takes event_mutex.
4. onmatch_destroy() and onmatch_create() have long call tree,
but both are finally invoked from event_trigger_regex_write()
and event_trace_del_tracer(), former takes event_mutex, and latter
ensures called under event_mutex locked.
Finally, I ensured there is no resource conflict. For safety,
I added lockdep_assert_held(&event_mutex) for each function.
Link: http://lkml.kernel.org/r/154140864134.17322.4796059721306031894.stgit@devbox
Reviewed-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Tested-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: George Guo <guodongtai@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_events_hist.c | 30 +++++++-----------------------
1 file changed, 7 insertions(+), 23 deletions(-)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -443,8 +443,6 @@ static bool have_hist_err(void)
return false;
}
-static DEFINE_MUTEX(synth_event_mutex);
-
struct synth_trace_event {
struct trace_entry ent;
u64 fields[];
@@ -1097,7 +1095,6 @@ static int __create_synth_event(int argc
return -EINVAL;
mutex_lock(&event_mutex);
- mutex_lock(&synth_event_mutex);
event = find_synth_event(name);
if (event) {
@@ -1139,7 +1136,6 @@ static int __create_synth_event(int argc
else
free_synth_event(event);
out:
- mutex_unlock(&synth_event_mutex);
mutex_unlock(&event_mutex);
return ret;
@@ -1159,7 +1155,6 @@ static int create_or_delete_synth_event(
/* trace_run_command() ensures argc != 0 */
if (name[0] == '!') {
mutex_lock(&event_mutex);
- mutex_lock(&synth_event_mutex);
event = find_synth_event(name + 1);
if (event) {
if (event->ref)
@@ -1173,7 +1168,6 @@ static int create_or_delete_synth_event(
}
} else
ret = -ENOENT;
- mutex_unlock(&synth_event_mutex);
mutex_unlock(&event_mutex);
return ret;
}
@@ -3660,7 +3654,7 @@ static void onmatch_destroy(struct actio
{
unsigned int i;
- mutex_lock(&synth_event_mutex);
+ lockdep_assert_held(&event_mutex);
kfree(data->onmatch.match_event);
kfree(data->onmatch.match_event_system);
@@ -3673,8 +3667,6 @@ static void onmatch_destroy(struct actio
data->onmatch.synth_event->ref--;
kfree(data);
-
- mutex_unlock(&synth_event_mutex);
}
static void destroy_field_var(struct field_var *field_var)
@@ -3810,15 +3802,14 @@ static int onmatch_create(struct hist_tr
struct synth_event *event;
int ret = 0;
- mutex_lock(&synth_event_mutex);
+ lockdep_assert_held(&event_mutex);
+
event = find_synth_event(data->onmatch.synth_event_name);
if (!event) {
hist_err("onmatch: Couldn't find synthetic event: ", data->onmatch.synth_event_name);
- mutex_unlock(&synth_event_mutex);
return -EINVAL;
}
event->ref++;
- mutex_unlock(&synth_event_mutex);
var_ref_idx = hist_data->n_var_refs;
@@ -3892,9 +3883,7 @@ static int onmatch_create(struct hist_tr
out:
return ret;
err:
- mutex_lock(&synth_event_mutex);
event->ref--;
- mutex_unlock(&synth_event_mutex);
goto out;
}
@@ -5611,6 +5600,8 @@ static void hist_unreg_all(struct trace_
struct synth_event *se;
const char *se_name;
+ lockdep_assert_held(&event_mutex);
+
if (hist_file_check_refs(file))
return;
@@ -5620,12 +5611,10 @@ static void hist_unreg_all(struct trace_
list_del_rcu(&test->list);
trace_event_trigger_enable_disable(file, 0);
- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref--;
- mutex_unlock(&synth_event_mutex);
update_cond_flag(file);
if (hist_data->enable_timestamps)
@@ -5651,6 +5640,8 @@ static int event_hist_trigger_func(struc
char *trigger, *p;
int ret = 0;
+ lockdep_assert_held(&event_mutex);
+
if (glob && strlen(glob)) {
last_cmd_set(param);
hist_err_clear();
@@ -5741,14 +5732,10 @@ static int event_hist_trigger_func(struc
}
cmd_ops->unreg(glob+1, trigger_ops, trigger_data, file);
-
- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref--;
- mutex_unlock(&synth_event_mutex);
-
ret = 0;
goto out_free;
}
@@ -5787,13 +5774,10 @@ enable:
if (ret)
goto out_unreg;
- mutex_lock(&synth_event_mutex);
se_name = trace_event_name(file->event_call);
se = find_synth_event(se_name);
if (se)
se->ref++;
- mutex_unlock(&synth_event_mutex);
-
/* Just return zero, not the number of registered triggers */
ret = 0;
out:
Patches currently in stable-queue which might be from kroah.com@xxxxxxxxxxxxxxx are
queue-4.19/tracing-consolidate-trace_add-remove_event_call-back-to-the-nolock-functions.patch
queue-4.19/tracing-split-up-onmatch-action-data.patch
queue-4.19/tracing-remove-unnecessary-var_ref-destroy-in-track_data_destroy.patch
queue-4.19/tracing-use-str_has_prefix-helper-for-histogram-code.patch
queue-4.19/tracing-simplify-creation-and-deletion-of-synthetic-events.patch
queue-4.19/tracing-refactor-hist-trigger-action-code.patch
queue-4.19/string.h-add-str_has_prefix-helper-function.patch
queue-4.19/tracing-remove-unneeded-synth_event_mutex.patch
queue-4.19/tracing-add-unified-dynamic-event-framework.patch
queue-4.19/tracing-use-dyn_event-framework-for-synthetic-events.patch
queue-4.19/tracing-use-str_has_prefix-instead-of-using-fixed-sizes.patch
queue-4.19/tracing-generalize-hist-trigger-onmax-and-save-action.patch
queue-4.19/tracing-have-the-historgram-use-the-result-of-str_has_prefix-for-len-of-prefix.patch
