Re: [PATCH] perf/core: Fix race between perf_event_exit_task and perf_pending_task

[Peter Zijlstra]

On Thu, Apr 16, 2026 at 03:34:43AM +0000, Luo Gengkun wrote:
> A race condition exists between perf_event_exit_task() and perf_pending_task().
> 
> During begin_new_exec(), perf_event_exit_task() may be called, and the
> PF_EXITING flag is not set on task. so perf_sigtrap() continues to execute
> and triggers WARN_ON_ONCE(event->ctx->task != current).
> 
> To fix this problem, also check if the event->ctx->task is TASK_TOMBSTONE.
> 
> Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events")
> Signed-off-by: Luo Gengkun <luogengkun2@xxxxxxxxxx>
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 1f5699b339ec..3422900263fa 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -7543,7 +7543,7 @@ static void perf_sigtrap(struct perf_event *event)
>  	 * Both perf_pending_task() and perf_pending_irq() can race with the
>  	 * task exiting.
>  	 */
> -	if (current->flags & PF_EXITING)
> +	if (current->flags & PF_EXITING || event->ctx->task == TASK_TOMBSTONE)
>  		return;

Since do_exit() also calls perf_event_exit_task() (albeit a little later
than exit_signals()), and task_can_queue_signal() will return false when
PF_EXITING, and we ignore the return value of
send_sig_perf()/send_sig_info(). I don't think we need to check both.

That is, I think:

	if (event->ctx->task == TASK_TOMBSTONE)

is sufficient. Also, the comment needs updating.