Messages in this thread | | | Date | Mon, 29 Jun 2020 16:02:46 +0200 | From | Oleg Nesterov <> | Subject | Re: wait_on_page_bit_common(TASK_KILLABLE, EXCLUSIVE) can miss wakeup? |
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On 06/29, Nicholas Piggin wrote: > > prepare_to_wait_event() has a pretty good pattern (and comment), I would > favour using that (test the signal when inserting on the waitqueue). > > @@ -1133,6 +1133,15 @@ static inline int wait_on_page_bit_common(wait_queue_head_t *q, > for (;;) { > spin_lock_irq(&q->lock); > > + if (signal_pending_state(state, current)) { > + /* Must not lose an exclusive wake up, see > + * prepare_to_wait_event comment */ > + list_del_init(&wait->entry); > + spin_unlock_irq(&q->lock); > + ret = -EINTR;
Basically this is what my patch in the 1st email does. But note that we can't just set "ret = -EINTR" here, we will need to clear "ret" if test_and_set_bit() below succeeds. That is why I used another "int intr" variable.
Oleg.
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