[for-next][PATCH 5/8] tracing: Do not synchronize freeing of trigger filter on boot up

Steven Rostedt
2022-12-14T14:02:27Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

If a trigger filter on the kernel command line fails to apply (due to
syntax error), it will be freed. The freeing will call
tracepoint_synchronize_unregister(), but this is not needed during early
boot up, and will even trigger a lockdep splat.

Avoid calling the synchronization function when system_state is
SYSTEM_BOOTING.

Link: https://lore.kernel.org/linux-trace-kernel/20221213172429.7774f4ba@gandalf.local.home

Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_events_trigger.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 19ce9d22bfd7..e535959939d3 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1085,8 +1085,14 @@ int set_trigger_filter(char *filter_str,
rcu_assign_pointer(data->filter, filter);

if (tmp) {
- /* Make sure the call is done with the filter */
- tracepoint_synchronize_unregister();
+ /*
+ * Make sure the call is done with the filter.
+ * It is possible that a filter could fail at boot up,
+ * and then this path will be called. Avoid the synchronization
+ * in that case.
+ */
+ if (system_state != SYSTEM_BOOTING)
+ tracepoint_synchronize_unregister();
free_event_filter(tmp);
}

--
2.35.1