Messages in this thread Patch in this message |  | | From | lirongqing <> | | Subject | [PATCH] sched/swait: Reduce lock contention in swake_up_all | | Date | Tue, 5 May 2026 05:04:31 -0400 |
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From: Li RongQing <lirongqing@baidu.com>
The entire task list have been moved a local list under the lock, it is unnecessary to hold the lock to wake tasks, This reduces lock operations from O(n) to O(1).
Move list_del_init before wake_up_state to prevent potential use-after-free if the woken task exits immediately and releases its memory.
Signed-off-by: Li RongQing <lirongqing@baidu.com> --- kernel/sched/swait.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c index 0fef649..ee4e658 100644 --- a/kernel/sched/swait.c +++ b/kernel/sched/swait.c @@ -66,19 +66,13 @@ void swake_up_all(struct swait_queue_head *q) raw_spin_lock_irq(&q->lock); list_splice_init(&q->task_list, &tmp); + raw_spin_unlock_irq(&q->lock); while (!list_empty(&tmp)) { curr = list_first_entry(&tmp, typeof(*curr), task_list); - wake_up_state(curr->task, TASK_NORMAL); list_del_init(&curr->task_list); - - if (list_empty(&tmp)) - break; - - raw_spin_unlock_irq(&q->lock); - raw_spin_lock_irq(&q->lock); + wake_up_state(curr->task, TASK_NORMAL); } - raw_spin_unlock_irq(&q->lock); } EXPORT_SYMBOL(swake_up_all); -- 2.9.4
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