Re: [PATCH rdma-rc 3/5] IB/umad: Return EPOLLERR in case of when device disassociated

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, Dec 13, 2020 at 03:29:38PM +0200, Leon Romanovsky wrote:
> From: Shay Drory <shayd@nvidia.com>
> 
> Currently, polling a umad device will always works, even if the device
> was disassociated. Hence, returning EPOLLERR if device was
> disassociated.

Grammar:

    Currently, polling a umad device will always work, even if the device was
    disassociated. A disassociated device should immediately return EPOLLERR
    from poll() and EIO from any read()/write(). Otherwise userspace is
    endlessly hung on poll() with no idea that the device has been removed
    from the system.
    

> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Shay Drory <shayd@nvidia.com>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
>  drivers/infiniband/core/user_mad.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
> index b671d4aede77..6681e9cf8a18 100644
> +++ b/drivers/infiniband/core/user_mad.c
> @@ -653,10 +653,14 @@ static __poll_t ib_umad_poll(struct file *filp, struct poll_table_struct *wait)
>  	/* we will always be able to post a MAD send */
>  	__poll_t mask = EPOLLOUT | EPOLLWRNORM;
> 
> +	mutex_lock(&file->mutex);
>  	poll_wait(filp, &file->recv_wait, wait);
> 
>  	if (!list_empty(&file->recv_list))
>  		mask |= EPOLLIN | EPOLLRDNORM;
> +	if (file->agents_dead)
> +		mask = EPOLLERR;

This also needs to trigger the recv_wait when agents_dead is set in
ib_umad_kill_port()

Jason