From: Eric Dumazet <dada1@cosmosbay.com>
To: Jens Axboe <jens.axboe@oracle.com>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] splice : two smp_mb() can be omitted
Date: Tue, 31 Oct 2006 08:41:45 +0100 [thread overview]
Message-ID: <4546FE39.8000201@cosmosbay.com> (raw)
In-Reply-To: <20061031073212.GW14055@kernel.dk>
Jens Axboe a écrit :
> On Tue, Oct 31 2006, Eric Dumazet wrote:
>> This patch deletes two calls to smp_mb() that were done after
>> mutex_unlock() that contains an implicit memory barrier.
>>
>> The first one in splice_to_pipe(), where 'do_wakeup' is set to true only if
>> pipe->inode is set (and in this case the
>> if (pipe->inode)
>> mutex_unlock(&pipe->inode->i_mutex);
>> is done too)
>>
>> The second one in link_pipe(), following inode_double_unlock() that
>> contains calls to mutex_unlock() too.
>
> NAK on that patch, the smp_mb() follows the waitqueue_active(). If you
> later change the code and move the locks or whatnot, you have lost that
> connection.
>
> If you change the patch to insert a comment, then it may be more
> applicable.
>
Hum... I read fs/pipe.c and see no smp_mb() there, but I suspect same
semantics are/were used.
Should we add comments on fs/pipe.c too ?
Eric
next prev parent reply other threads:[~2006-10-31 7:41 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-30 9:03 [PATCH 1/2] lockdep: spin_lock_irqsave_nested() Peter Zijlstra
2006-10-30 9:06 ` [PATCH 2/2] lockdep: annotate bcsp driver Peter Zijlstra
2006-10-30 9:06 ` Ingo Molnar
2006-10-30 9:30 ` Marcel Holtmann
2006-10-30 9:31 ` [PATCH 2/2] lockdep: annotate bcsp driver - v2 Peter Zijlstra
2006-10-30 9:07 ` [PATCH 1/2] lockdep: spin_lock_irqsave_nested() Ingo Molnar
2006-10-30 13:12 ` Jarek Poplawski
2006-10-30 13:27 ` Jarek Poplawski
2006-10-30 13:40 ` [PATCH 1/2] lockdep: spin_lock_irqsave_nested() -v2 Peter Zijlstra
2006-10-30 14:12 ` Jarek Poplawski
2006-10-31 6:48 ` [PATCH 1/2] lockdep: spin_lock_irqsave_nested() Andrew Morton
2006-10-31 7:25 ` [PATCH] splice : two smp_mb() can be omitted Eric Dumazet
2006-10-31 7:32 ` Jens Axboe
2006-10-31 7:41 ` Eric Dumazet [this message]
2006-10-31 7:46 ` Jens Axboe
2006-10-31 9:40 ` Nick Piggin
2006-10-31 9:49 ` Jens Axboe
2006-10-31 10:51 ` Eric Dumazet
2006-10-31 22:16 ` Nick Piggin
2006-10-31 23:08 ` Eric Dumazet
2006-10-31 23:45 ` Nick Piggin
2006-11-02 17:02 ` [PATCH] splice : Must fully check for fifos Eric Dumazet
2006-11-02 17:05 ` Eric Dumazet
2006-11-02 19:07 ` Jens Axboe
2006-11-03 8:50 ` 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=4546FE39.8000201@cosmosbay.com \
--to=dada1@cosmosbay.com \
--cc=akpm@osdl.org \
--cc=jens.axboe@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
/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