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

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Message-ID: <0acf040c-4b00-1647-e0c9-fc8b1c94685d@kernel.dk>
Date:   Fri, 7 Feb 2020 09:12:39 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Stefano Garzarella <sgarzare@...hat.com>
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 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.

-- 
Jens Axboe