Message-ID: <3F303430.1080908@aros.net>
Date: Tue, 05 Aug 2003 16:48:16 -0600
From: Lou Langholtz <ldl@aros.net>
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To: Paul Clements <Paul.Clements@SteelEye.com>
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> <3F300760.8F703814@SteelEye.com>
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Paul Clements wrote:

>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
>  
>
Except that in the error case, the send basically didn't succeed. So no 
need to worry about recieving a reply and no race possibility in that case.

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