Reading the sched_cmdline_ref and sched_tgid_ref initial state within tracing_start_sched_switch without holding the sched_register_mutex is racy against concurrent updates, which can lead to tracepoint probes being registered more than once (and thus trigger warnings within tracepoint.c).
[ Compile-tested only. I suspect it might fix the following syzbot report: [email protected] ] Signed-off-by: Mathieu Desnoyers <[email protected]> CC: Steven Rostedt (VMware) <[email protected]> CC: Joel Fernandes (Google) <[email protected]> CC: Peter Zijlstra <[email protected]> CC: Thomas Gleixner <[email protected]> CC: Paul E. McKenney <[email protected]> --- kernel/trace/trace_sched_switch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c index e288168661e1..e304196d7c28 100644 --- a/kernel/trace/trace_sched_switch.c +++ b/kernel/trace/trace_sched_switch.c @@ -89,8 +89,10 @@ static void tracing_sched_unregister(void) static void tracing_start_sched_switch(int ops) { - bool sched_register = (!sched_cmdline_ref && !sched_tgid_ref); + bool sched_register; + mutex_lock(&sched_register_mutex); + sched_register = (!sched_cmdline_ref && !sched_tgid_ref); switch (ops) { case RECORD_CMDLINE: -- 2.11.0
