Message-ID: <3F300760.8F703814@SteelEye.com>
Date: Tue, 05 Aug 2003 15:37:04 -0400
From: Paul Clements <Paul.Clements@SteelEye.com>
MIME-Version: 1.0
To: Lou Langholtz <ldl@aros.net>
CC: linux-kernel <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] 2.6.0 NBD driver: remove send/recieve race for request
References: <3F2FE078.6020305@aros.net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1032
Lines: 24

Lou Langholtz wrote:
> 
> The following patch removes a race condition in the network block device
> driver in 2.6.0*. Without this patch, the reply receiving thread could
> end (and free up the memory for) the request structure before the
> request sending thread is completely done accessing it and would then
> access invalid memory.

Indeed, there is a race condition here. It's a very small window, but it
looks like it could possibly be trouble on SMP/preempt kernels.

This patch looks OK, but it appears to still leave the race window open
in the error case (it seems to fix the non-error case, though). We
probably could actually use the ref_count field of struct request to
better fix this problem. I'll take a look at doing this, and send a
patch out in a while.

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