linux-kernel - Re: [PATCH] io_uring: flush overflowed CQ events in the io_uring

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Message-ID: <20200207163853.bzfgn2mzpactehk3@steredhat>
Date:   Fri, 7 Feb 2020 17:38:53 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        io-uring@...r.kernel.org
Subject: Re: [PATCH] io_uring: flush overflowed CQ events in the
 io_uring_poll()

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