tracing: Do not synchronize freeing of trigger filter on boot up

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/[email protected]

Cc: Andrew Morton <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

1 files 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);
 	}