[PATCH] tracing: skip boot kprobe setup when no events were requested

[Wenwen Fu]

setup_boot_kprobe_events() calls enable_boot_kprobe_events() even when
the kprobe_event= boot parameter was not supplied. That call takes
event_mutex without any command-line probes to enable.

Asynchronous eval-map updates also hold event_mutex. A normal boot can
therefore wait in init_kprobe_trace() for this background work despite
having no boot probes to set up.

Return early when the boot-event buffer is empty. Keep the mutex
protection in trace_event_update_all() and retain setup for explicit
kprobe_event= parameters. Bootconfig handles its own probe enablement,
and the existing trace_eval_sync() still waits for background work
before init memory is freed.

Signed-off-by: Wenwen Fu <wenwfu@xxxxxxxxxxxxxxxx>
---
 kernel/trace/trace_kprobe.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ee8171b19bee..52ec16d8d838 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1995,6 +1995,9 @@ static __init void setup_boot_kprobe_events(void)
 	char *p, *cmd = kprobe_boot_events_buf;
 	int ret;
 
+	if (!kprobe_boot_events_buf[0])
+		return;
+
 	strreplace(kprobe_boot_events_buf, ',', ' ');
 
 	while (cmd && *cmd != '\0') {