netdev - Re: [PATCH] net/flow: remove sleeping and deferral mechanism from flow_cache

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Message-Id: <20111221.164836.1819643617176570312.davem@davemloft.net>
Date:	Wed, 21 Dec 2011 16:48:36 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	timo.teras@....fi
Cc:	steffen.klassert@...unet.com, madalin.bucur@...escale.com,
	eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net/flow: remove sleeping and deferral mechanism from
 flow_cache_flush

From: Timo Teräs <timo.teras@....fi>
Date: Tue, 20 Dec 2011 10:41:40 +0200

> On 12/20/2011 10:23 AM, Steffen Klassert wrote:
>> On Tue, Sep 27, 2011 at 03:31:32PM -0400, David Miller wrote:
>>> From: David Miller <davem@...emloft.net>
>>> Date: Tue, 27 Sep 2011 15:28:36 -0400 (EDT)
>>>
>>>> afinfo->garbage_collect is the only other place __xfrm_garbage_collect
>>>> is referenced, and that is completely unused and should thus be deleted
>>>> (I'll take care of that in net-next).
>>>
>>> Nevermind I see how these are referenced directly via xfrm4_policy.c
>>> and xfrm6_policy.c, sigh...
>> 
>> Is there any progress in fixing this issue? I've seen this occasionally
>> on some of our production systems, so I fixed it for us in the meantime
>> with the patch below. I could submit this for inclusion if noone else
>> wants to fix it in a different manner.
>> 
>> ------
>> net: Add a flow_cache_flush_deferred function
>> 
>> flow_cach_flush() might sleep but can be called from
>> atomic context via the xfrm garbage collector. So add
>> a flow_cache_flush_deferred() function and use this if
>> the xfrm garbage colector is invoked from within the
>> packet path.
>> 
>> Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> 
> Acked-by: Timo Teräs <timo.teras@....fi>
> 
> I was first thinking if it made sense to run the local CPUs task
> immediately on gc. But since all it does is queue the removed nodes to
> the second gc that actually frees the dst's, it doesn't really make a
> difference.
> 
> So this is probably as good as it gets.

Applied, thanks everyone.
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