___wait_event() doesn't really need abort_exclusive_wait(), we can simply change prepare_to_wait_event() to remove the waiter from q->task_list if it was interrupted.
This simplifies the code/logic, and this way prepare_to_wait_event() can have more users, see the next change. Signed-off-by: Oleg Nesterov <[email protected]> --- include/linux/wait.h | 7 +------ kernel/sched/wait.c | 23 ++++++++++++++++++----- 2 files changed, 19 insertions(+), 11 deletions(-) diff --git a/include/linux/wait.h b/include/linux/wait.h index 329f796..5179915 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -280,12 +280,7 @@ wait_queue_head_t *bit_waitqueue(void *, int); \ if (___wait_is_interruptible(state) && __int) { \ __ret = __int; \ - if (exclusive) { \ - abort_exclusive_wait(&wq, &__wait, \ - NULL); \ - goto __out; \ - } \ - break; \ + goto __out; \ } \ \ cmd; \ diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 2bbba01..4af0dc8 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -199,15 +199,28 @@ EXPORT_SYMBOL(prepare_to_wait_exclusive); long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state) { unsigned long flags; - - if (signal_pending_state(state, current)) - return -ERESTARTSYS; + long ret = 0; wait->private = current; wait->func = autoremove_wake_function; spin_lock_irqsave(&q->lock, flags); - if (list_empty(&wait->task_list)) { + if (unlikely(signal_pending_state(state, current))) { + /* + * Exclusive waiter must not fail if it was selected by wakeup, + * it should "consume" the condition we were waiting for. + * + * The caller will recheck the condition and return success if + * we were already woken up, we can not miss the event because + * wakeup locks/unlocks the same q->lock. + * + * But we need to ensure that set-condition + wakeup after that + * can't see us, it should wake up another exclusive waiter if + * we fail. + */ + list_del_init(&wait->task_list); + ret = -ERESTARTSYS; + } else if (list_empty(&wait->task_list)) { if (wait->flags & WQ_FLAG_EXCLUSIVE) __add_wait_queue_tail(q, wait); else @@ -216,7 +229,7 @@ long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state) set_current_state(state); spin_unlock_irqrestore(&q->lock, flags); - return 0; + return ret; } EXPORT_SYMBOL(prepare_to_wait_event); -- 2.5.0
