Commit 8feb053d authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched: Fix trace_sched_switch(.prev_state) 



Gabriele noted that in case of signal_pending_state(), the tracepoint
sees a stale task-state.

Fixes: fa2c3254 ("sched/tracing: Don't re-read p->state when emitting sched_switch event")
Reported-by: default avatarGabriele Monaco <gmonaco@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Valentin Schneider <vschneid@redhat.com>
parent 3e816361

kernel/sched/core.c

+4 −2
Original line number Diff line number Diff line
@@ -6571,12 +6571,14 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) 
 * Otherwise marks the task's __state as RUNNING

 */

static bool try_to_block_task(struct rq *rq, struct task_struct *p,

			      unsigned long task_state)

			      unsigned long *task_state_p)

{

	unsigned long task_state = *task_state_p;

	int flags = DEQUEUE_NOCLOCK;



	if (signal_pending_state(task_state, p)) {

		WRITE_ONCE(p->__state, TASK_RUNNING);

		*task_state_p = TASK_RUNNING;

		return false;

	}
@@ -6713,7 +6715,7 @@ static void __sched notrace __schedule(int sched_mode) 
			goto picked;

		}

	} else if (!preempt && prev_state) {

		try_to_block_task(rq, prev, prev_state);

		try_to_block_task(rq, prev, &prev_state);

		switch_count = &prev->nvcsw;

	}