On Tue, Sep 24, 2019 at 02:11:29PM +0300, Pavel Begunkov wrote:
> @@ -2717,15 +2757,18 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
> return ret;
> }
>
> + iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
> + prepare_to_wait_exclusive(&ctx->wait, &iowq.wq, TASK_INTERRUPTIBLE);
> + do {
> + if (io_should_wake(&iowq))
> + break;
> + schedule();
> + if (signal_pending(current))
> + break;
> + set_current_state(TASK_INTERRUPTIBLE);
> + } while (1);
> + finish_wait(&ctx->wait, &iowq.wq);
It it likely OK, but for paranoia, I'd prefer this form:
for (;;) {
prepare_to_wait_exclusive(&ctx->wait, &iowq.wq, TASK_INTERRUPTIBLE);
if (io_should_wake(&iowq))
break;
schedule();
if (signal_pending(current))
break;
}
finish_wait(&ctx->wait, &iowq.wq);
The thing is, if we ever succeed with io_wake_function() (that CPU
observes io_should_wake()), but when waking here, we do not observe
is_wake_function() and go sleep again, we might never wake up if we
don't put ourselves back on the wait-list again.
