Re: [PATCH] RDMA/uverbs: Make the event_queue fds return POLLERR when disassociated

[Leon Romanovsky <leon@kernel.org>]

On Mon, Apr 06, 2020 at 09:44:26PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
>
> If is_closed is set, and the event list is empty, then read() will return
> -EIO without blocking. After setting is_closed in
> ib_uverbs_free_event_queue(), we do trigger a wake_up on the poll_wait,
> but the fops->poll() function does not check it, so poll will continue to
> sleep on an empty list.
>
> Fixes: 14e23bd6d221 ("RDMA/core: Fix locking in ib_uverbs_event_read")
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
> ---
>  drivers/infiniband/core/uverbs_main.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
> index 2d4083bf4a0487..8710a3427146e7 100644
> --- a/drivers/infiniband/core/uverbs_main.c
> +++ b/drivers/infiniband/core/uverbs_main.c
> @@ -296,6 +296,8 @@ static __poll_t ib_uverbs_event_poll(struct ib_uverbs_event_queue *ev_queue,
>  	spin_lock_irq(&ev_queue->lock);
>  	if (!list_empty(&ev_queue->event_list))
>  		pollflags = EPOLLIN | EPOLLRDNORM;
> +	else if (ev_queue->is_closed)
> +		pollflags = EPOLLERR;
>  	spin_unlock_irq(&ev_queue->lock);

Don't you need to set EPOLLHUP too? Probably, it won't change anything,
just for the sake of the correctness.

Thanks,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>