If thread is preempted before calling set_current_state(TASK_INTERRUPTIBLE), and the other thread set the condition followed with wake_up_process. After that when this thread is re-scheduled, calling set_current_state to set itself as state TASK_INTERRUPTIBLE, if it is preempted again after that and before __set_current_state(TASK_RUNNING), it triggers the invalid wakeup problem.
To solve this problem, using preempt_disable() to bound the operaion that setting the task state and the conditions(set by the wake thread) validation. Signed-off-by: Libin <[email protected]> --- kernel/workqueue.c | 92 +++++++++++++++++++++++++++++------------------------- 1 file changed, 49 insertions(+), 43 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 7f5d4be..2dcdd30 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2358,63 +2358,69 @@ static int rescuer_thread(void *__rescuer) * doesn't participate in concurrency management. */ rescuer->task->flags |= PF_WQ_WORKER; -repeat: - set_current_state(TASK_INTERRUPTIBLE); + for (;;) { - if (kthread_should_stop()) { + if (kthread_should_stop()) { + rescuer->task->flags &= ~PF_WQ_WORKER; + return 0; + } + + preempt_disable(); + set_current_state(TASK_INTERRUPTIBLE); + if (list_empty(&wq->maydays)) { + preempt_enable(); + schedule(); + preempt_disable(); + } __set_current_state(TASK_RUNNING); - rescuer->task->flags &= ~PF_WQ_WORKER; - return 0; - } + preempt_enable(); - /* see whether any pwq is asking for help */ - spin_lock_irq(&wq_mayday_lock); + /* see whether any pwq is asking for help */ + spin_lock_irq(&wq_mayday_lock); - while (!list_empty(&wq->maydays)) { - struct pool_workqueue *pwq = list_first_entry(&wq->maydays, + while (!list_empty(&wq->maydays)) { + struct pool_workqueue *pwq = list_first_entry(&wq->maydays, struct pool_workqueue, mayday_node); - struct worker_pool *pool = pwq->pool; - struct work_struct *work, *n; + struct worker_pool *pool = pwq->pool; + struct work_struct *work, *n; - __set_current_state(TASK_RUNNING); - list_del_init(&pwq->mayday_node); + list_del_init(&pwq->mayday_node); - spin_unlock_irq(&wq_mayday_lock); + spin_unlock_irq(&wq_mayday_lock); - /* migrate to the target cpu if possible */ - worker_maybe_bind_and_lock(pool); - rescuer->pool = pool; + /* migrate to the target cpu if possible */ + worker_maybe_bind_and_lock(pool); + rescuer->pool = pool; - /* - * Slurp in all works issued via this workqueue and - * process'em. - */ - WARN_ON_ONCE(!list_empty(&rescuer->scheduled)); - list_for_each_entry_safe(work, n, &pool->worklist, entry) - if (get_work_pwq(work) == pwq) - move_linked_works(work, scheduled, &n); + /* + * Slurp in all works issued via this workqueue and + * process'em. + */ + WARN_ON_ONCE(!list_empty(&rescuer->scheduled)); + list_for_each_entry_safe(work, n, &pool->worklist, entry) + if (get_work_pwq(work) == pwq) + move_linked_works(work, scheduled, &n); - process_scheduled_works(rescuer); + process_scheduled_works(rescuer); - /* - * Leave this pool. If keep_working() is %true, notify a - * regular worker; otherwise, we end up with 0 concurrency - * and stalling the execution. - */ - if (keep_working(pool)) - wake_up_worker(pool); + /* + * Leave this pool. If keep_working() is %true, notify a + * regular worker; otherwise, we end up with 0 concurrency + * and stalling the execution. + */ + if (keep_working(pool)) + wake_up_worker(pool); - rescuer->pool = NULL; - spin_unlock(&pool->lock); - spin_lock(&wq_mayday_lock); - } + rescuer->pool = NULL; + spin_unlock(&pool->lock); + spin_lock(&wq_mayday_lock); + } - spin_unlock_irq(&wq_mayday_lock); + spin_unlock_irq(&wq_mayday_lock); - /* rescuers should never participate in concurrency management */ - WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); - schedule(); - goto repeat; + /* rescuers should never participate in concurrency management */ + WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); + } } struct wq_barrier { -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
