io-uring.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>,
	Nathan Chancellor <natechancellor@gmail.com>
Cc: io-uring@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH 2/2] io_uring: optimise io_fail_links()
Date: Thu, 15 Oct 2020 07:09:11 -0600	[thread overview]
Message-ID: <01c6d077-f6fa-a8da-449a-d0c1c4d59012@kernel.dk> (raw)
In-Reply-To: <7e293894-823c-5b91-1b55-f5941c82d83e@gmail.com>

On 10/15/20 4:11 AM, Pavel Begunkov wrote:
> On 15/10/2020 09:53, Nathan Chancellor wrote:
>> On Wed, Oct 14, 2020 at 08:44:22PM +0100, Pavel Begunkov wrote:
>>> -		io_put_req_deferred(link, 2);
>>> +
>>> +		/*
>>> +		 * It's ok to free under spinlock as they're not linked anymore,
>>> +		 * but avoid REQ_F_WORK_INITIALIZED because it may deadlock on
>>> +		 * work.fs->lock.
>>> +		 */
>>> +		if (link->flags | REQ_F_WORK_INITIALIZED)
>>> +			io_put_req_deferred(link, 2);
>>> +		else
>>> +			io_double_put_req(link);
>>
>> fs/io_uring.c:1816:19: warning: bitwise or with non-zero value always
>> evaluates to true [-Wtautological-bitwise-compare]
>>                 if (link->flags | REQ_F_WORK_INITIALIZED)
>>                     ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
>> 1 warning generated.
>>
>> According to the comment, was it intended for that to be a bitwise AND
>> then negated to check for the absence of it? If so, wouldn't it be
>> clearer to flip the condition so that a negation is not necessary like
>> below? I can send a formal patch if my analysis is correct but if not,
>> feel free to fix it yourself and add
> 
> I have no idea what have happened, but yeah, there should be "&",
> though without any additional negation. That's because deferred
> version is safer. 
> 
> Nathan, thanks for letting know!
> Jens, could you please fold in the change below.

Done.

-- 
Jens Axboe


  reply	other threads:[~2020-10-15 13:09 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14 19:44 [PATCH 0/2] post F_COMP_LOCKED optimisations Pavel Begunkov
2020-10-14 19:44 ` [PATCH 1/2] io_uring: optimise COMP_LOCK-less flush_completion Pavel Begunkov
2020-10-14 19:44 ` [PATCH 2/2] io_uring: optimise io_fail_links() Pavel Begunkov
2020-10-15  8:53   ` Nathan Chancellor
2020-10-15 10:11     ` Pavel Begunkov
2020-10-15 13:09       ` Jens Axboe [this message]
2020-10-14 19:53 ` [PATCH 0/2] post F_COMP_LOCKED optimisations Jens Axboe
2020-10-14 20:00   ` Pavel Begunkov
2020-10-14 20:24     ` Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=01c6d077-f6fa-a8da-449a-d0c1c4d59012@kernel.dk \
    --to=axboe@kernel.dk \
    --cc=asml.silence@gmail.com \
    --cc=clang-built-linux@googlegroups.com \
    --cc=io-uring@vger.kernel.org \
    --cc=natechancellor@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).