[PATCH] tracing: Drop the synthetic event ref when clearing hist triggers
DORMANTno replies
From: David Carlier <hidden>
Date: 2026-10-22 20:54:10
Also in:
lkml, stable
Subsystem:
the rest, tracing · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
clear_event_triggers() frees a hist trigger on a synthetic event without
dropping the se->ref taken by event_hist_trigger_parse(). Removing an
instance with such a trigger leaves the synthetic event busy forever.
Fixes: 4b147936fa50 ("tracing: Add support for 'synthetic' events")
Cc: stable@vger.kernel.org
Signed-off-by: David Carlier <redacted>
---
Applies on trace/for-next, depends on 3403d9bb27eb ("tracing/histograms: Verify event_call identity when updating synth_event refcount").
kernel/trace/trace.h | 2 ++
kernel/trace/trace_events_hist.c | 20 +++++++++++++-------
kernel/trace/trace_events_trigger.c | 2 ++
3 files changed, 17 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 0f0786700f99..e108f95fd609 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h@@ -1915,9 +1915,11 @@ extern const struct file_operations event_inject_fops; #ifdef CONFIG_HIST_TRIGGERS extern int register_trigger_hist_cmd(void); extern int register_trigger_hist_enable_disable_cmds(void); +extern void hist_put_synth_event(struct trace_event_file *file); #else static inline int register_trigger_hist_cmd(void) { return 0; } static inline int register_trigger_hist_enable_disable_cmds(void) { return 0; } +static inline void hist_put_synth_event(struct trace_event_file *file) { } #endif extern int register_trigger_cmds(void);
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index f39fa8942673..9419edfd1b67 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c@@ -6756,6 +6756,17 @@ static bool hist_trigger_check_refs(struct event_trigger_data *data, return false; } +void hist_put_synth_event(struct trace_event_file *file) +{ + struct synth_event *se; + + lockdep_assert_held(&event_mutex); + + se = find_synth_event_call(file->event_call); + if (se) + se->ref--; +} + static void hist_unregister_trigger(char *glob, struct event_trigger_data *data, struct trace_event_file *file)
@@ -6811,7 +6822,6 @@ static void hist_unreg_all(struct trace_event_file *file) { struct event_trigger_data *test, *n; struct hist_trigger_data *hist_data; - struct synth_event *se; lockdep_assert_held(&event_mutex);
@@ -6824,9 +6834,7 @@ static void hist_unreg_all(struct trace_event_file *file) list_del_rcu(&test->list); trace_event_trigger_enable_disable(file, 0); - se = find_synth_event_call(file->event_call); - if (se) - se->ref--; + hist_put_synth_event(file); update_cond_flag(file); if (hist_data->enable_timestamps)
@@ -6941,9 +6949,7 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops, } event_trigger_unregister(cmd_ops, file, glob+1, trigger_data); - se = find_synth_event_call(file->event_call); - if (se) - se->ref--; + hist_put_synth_event(file); ret = 0; goto out_free; }
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 4d2fde996c0f..a2487ad7fef8 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c@@ -643,6 +643,8 @@ clear_event_triggers(struct trace_array *tr) list_for_each_entry_safe(data, n, &file->triggers, list) { trace_event_trigger_enable_disable(file, 0); list_del_rcu(&data->list); + if (data->cmd_ops->trigger_type == ETT_EVENT_HIST) + hist_put_synth_event(file); if (data->cmd_ops->free) data->cmd_ops->free(data); }
--
2.55.0