netdev - Re: [PATCH stable 3.4 1/2] ipv4: move route garbage collector to work queue

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Date:	Wed, 13 Aug 2014 03:50:02 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	David Miller <davem@...emloft.net>
Cc:	hannes@...hat.com, eric.dumazet@...il.com, mleitner@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH stable 3.4 1/2] ipv4: move route garbage collector to work
 queue

Hi David,

On Wed, Aug 13, 2014, at 02:46, David Miller wrote:
> From: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Date: Wed, 13 Aug 2014 01:11:14 +0200
> 
> > On Wed, Aug 13, 2014, at 00:42, David Miller wrote:
> >> Just bite the bullet and put a spinlock around the GC operation.
> > 
> > We had a spinlock around the GC operation at first but still were
> > capable to cause softlockups, I don't remember if a complete lockup
> > happend.
> 
> This much I understand.
> 
> What I'm saying is retain this patch #1, in order to make the normal
> GCs run asynchronously via a work queue, but on top of that put a
> spinlock around the GC function.

I understood you correctly. ;)

The spin_lock would need to be _bh protected as it can be called from
softirq as well as in the wq. IIRC that was the problem. I'll follow up
with Marcelo to find a solution for this.

Thanks,
Hannes
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