Re: [PATCH] io_uring: flush overflowed CQ events in the io_uring_poll()

From: Stefano Garzarella <sgarzare@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	io-uring@vger.kernel.org
Subject: Re: [PATCH] io_uring: flush overflowed CQ events in the io_uring_poll()
Date: Fri, 7 Feb 2020 17:38:53 +0100	[thread overview]
Message-ID: <20200207163853.bzfgn2mzpactehk3@steredhat> (raw)
In-Reply-To: <0acf040c-4b00-1647-e0c9-fc8b1c94685d@kernel.dk>

On Fri, Feb 07, 2020 at 09:12:39AM -0700, Jens Axboe wrote:
> On 2/7/20 5:18 AM, Stefano Garzarella wrote:
> > In io_uring_poll() we must flush overflowed CQ events before to
> > check if there are CQ events available, to avoid missing events.
> > 
> > We call the io_cqring_events() that checks and flushes any overflow
> > and returns the number of CQ events available.
> > 
> > We can avoid taking the 'uring_lock' since the flush is already
> > protected by 'completion_lock'.
> 
> Thanks, applied. I dropped that last sentence, as a) it doesn't
> really matter, and b) we may very well already have it held here
> if someone is doing a poll on the io_uring fd itself.

Sure, indeed I was undecided whether to put it after the three dashes
as a response to your yesterday's request.

Thanks,
Stefano