linux-kernel - Re: [PATCH] splice : two smp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20061031073212.GW14055@kernel.dk>
Date:	Tue, 31 Oct 2006 08:32:12 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	Andrew Morton <akpm@...l.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] splice : two smp_mb() can be omitted

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.

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/