[tip: sched/core] sched: Be more strict about p->is_blocked

["tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     708024b575b4ea58c5956e7c09f2d2f48facd478
Gitweb:        https://git.kernel.org/tip/708024b575b4ea58c5956e7c09f2d2f48facd478
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Tue, 26 May 2026 11:32:34 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 02 Jun 2026 12:26:08 +02:00

sched: Be more strict about p->is_blocked

Upon entry to try_to_block_task(), p->is_blocked should be false. After all,
the prior wakeup would have made it so per ttwu_do_wakeup().

Ensure this is the case, rather than clearing it in the path that doesn't set
it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260526113322.364017314%40infradead.org
---
 kernel/sched/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a06d5a5..8b7eb12 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6676,8 +6676,9 @@ static bool try_to_block_task(struct rq *rq, struct task_struct *p,
 {
 	unsigned long task_state = *task_state_p;
 
+	WARN_ON_ONCE(p->is_blocked);
+
 	if (signal_pending_state(task_state, p)) {
-		p->is_blocked = 0;
 		WRITE_ONCE(p->__state, TASK_RUNNING);
 		*task_state_p = TASK_RUNNING;
 		clear_task_blocked_on(p, NULL);