Re: [PATCH v2] tracing: Restore synchronize_rcu() before freeing trigger private data
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2026-07-23 17:37:38
Also in:
lkml
On Thu, 23 Jul 2026 18:02:12 +0100 David Carlier [off-list ref] wrote:
quoted hunk ↗ jump to hunk
--- kernel/trace/trace_events_hist.c | 3 +++ kernel/trace/trace_events_trigger.c | 1 + 2 files changed, 4 insertions(+)diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 82ce492ab268..ddd2f70dac4f 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c@@ -6349,6 +6349,8 @@ static void event_hist_trigger_free(struct event_trigger_data *data) trigger_data_free(data); + synchronize_rcu();
According to Sashiko[1], it appears we actually need tracepoint_synchronize_unregister(). And I believe Sashiko is actually correct.
quoted hunk ↗ jump to hunk
+ remove_hist_vars(hist_data); unregister_field_var_hists(hist_data);@@ -6388,6 +6390,7 @@ static void event_hist_trigger_named_free(structevent_trigger_data *data) del_named_trigger(data); trigger_data_free(data); + synchronize_rcu();
This needs to be changed too.
quoted hunk ↗ jump to hunk
kfree(cmd_ops); } }diff --git a/kernel/trace/trace_events_trigger.cb/kernel/trace/trace_events_trigger.c index 655db2e82513..c3f54f2540b6 100644 --- a/kernel/trace/trace_events_trigger.c+++ b/kernel/trace/trace_events_trigger.c@@ -1730,6 +1730,7 @@ void event_enable_trigger_free(structevent_trigger_data *data) trace_event_enable_disable(enable_data->file, 0, 1); trace_event_put_ref(enable_data->file->event_call); trigger_data_free(data); + synchronize_rcu();
According to Sashiko, this one basically causes a revert of the original delay. OK, let's bring back a partial part of your original patch. Have the "free_private()" again, but only apply it to this trigger, and switch the above other to synchronize_rcu() into the tracepoint_synchronize_unregister(). Thanks, -- Steve
kfree(enable_data); }
[1] https://sashiko.dev/#/patchset/20260723170212.55325-1-devnexen%40gmail.com