Merge tag 'sched_urgent_for_v6.14_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

ff3b373e · Linus Torvalds <[email protected]> · 2025-02-16 10:38:24 -08:00

Pull scheduler fix from Borislav Petkov:

 - Clarify what happens when a task is woken up from the wake queue and
   make clear its removal from that queue is atomic

* tag 'sched_urgent_for_v6.14_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Clarify wake_up_q()'s write to task->wake_q.next

Commit: ff3b373ecc88098103b6ae80d96d6527210b2e64
Parents: 592c358e · bcc6244e

Merge commit. Changes below are compared with the first parent: 592c358e.

Changes

1 files changed · +3 −2

File	Status	Add	Del	Content
kernel/sched/core.c	modified	+3	−2	View file

kernel/sched/core.c

View file

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5404a30..9aecd91 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1063,9 +1063,10 @@ void wake_up_q(struct wake_q_head *head)
 		struct task_struct *task;
 
 		task = container_of(node, struct task_struct, wake_q);
-		/* Task can safely be re-inserted now: */
 		node = node->next;
-		task->wake_q.next = NULL;
+		/* pairs with cmpxchg_relaxed() in __wake_q_add() */
+		WRITE_ONCE(task->wake_q.next, NULL);
+		/* Task can safely be re-inserted now. */
 
 		/*
 		 * wake_up_process() executes a full barrier, which pairs with