Pavel Begunkov <asml.silence@xxxxxxxxx> writes:
> When io_poll_check_events() collides with someone attempting to queue a
> task work, it'll spin for one more time. However, it'll continue to use
> the mask from the first iteration instead of updating it. For example,
> if the first wake up was a EPOLLIN and the second EPOLLOUT, the
> userspace will not get EPOLLOUT in time.
>
> Clear the mask for all subsequent iterations to force vfs_poll().
Do we have a reproducer for it in liburing? Either way, I checked the
code, it looks good to me.
Reviewed-by: Gabriel Krisman Bertazi <krisman@xxxxxxx>
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: aa43477b04025 ("io_uring: poll rework")
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> io_uring/poll.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/io_uring/poll.c b/io_uring/poll.c
> index f500506984ec..90920abf91ff 100644
> --- a/io_uring/poll.c
> +++ b/io_uring/poll.c
> @@ -258,6 +258,9 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
> return ret;
> }
>
> + /* force the next iteration to vfs_poll() */
> + req->cqe.res = 0;
> +
> /*
> * Release all references, retry if someone tried to restart
> * task_work while we were executing it.
--
Gabriel Krisman Bertazi
