netdev - Re: [PATCH stable 3.4 2/2] ipv4: avoid parallel route cache gc executions

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Date:	Tue, 12 Aug 2014 20:50:37 +0200
From:	Hannes Frederic Sowa <hannes@...hat.com>
To:	Marcelo Ricardo Leitner <mleitner@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH stable 3.4 2/2] ipv4: avoid parallel route cache gc
 executions

On Mo, 2014-08-11 at 19:41 -0300, Marcelo Ricardo Leitner wrote:
> When rt_intern_hash() has to deal with neighbour cache overflowing,
> it triggers the route cache garbage collector in an attempt to free
> some references on neighbour entries.
> 
> Such call cannot be done async but should also not run in parallel with
> an already-running one, so that they don't collapse fighting over the
> hash lock entries.
> 
> This patch thus blocks parallel executions by ignoring the call if
> garbage collector is already running on another CPU.
> 
> We don't use a spinlock for it because now it runs on a work queue and
> we want it to be schedulable in-between the hash indexes.
> 
> Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com>
> Cc: Hannes Frederic Sowa <hannes@...hat.com>

Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>


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