Re: [PATCH stable v3.2 v3.4] ipv4: disable bh while doing route gc

From: Ben Hutchings <ben@decadent.org.uk>
To: David Miller <davem@davemloft.net>
Cc: mleitner@redhat.com, stable@vger.kernel.org,
	netdev@vger.kernel.org, hannes@stressinduktion.org
Subject: Re: [PATCH stable v3.2 v3.4] ipv4: disable bh while doing route gc
Date: Mon, 20 Oct 2014 04:09:41 +0100	[thread overview]
Message-ID: <1413774581.31953.12.camel@decadent.org.uk> (raw)
In-Reply-To: <20141013.135127.1915115817707962111.davem@davemloft.net>

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On Mon, 2014-10-13 at 13:51 -0400, David Miller wrote:
> From: Marcelo Ricardo Leitner <mleitner@redhat.com>
> Date: Mon, 13 Oct 2014 14:03:30 -0300
> 
> > Further tests revealed that after moving the garbage collector to a work
> > queue and protecting it with a spinlock may leave the system prone to
> > soft lockups if bottom half gets very busy.
> > 
> > It was reproced with a set of firewall rules that REJECTed packets. If
> > the NIC bottom half handler ends up running on the same CPU that is
> > running the garbage collector on a very large cache, the garbage
> > collector will not be able to do its job due to the amount of work
> > needed for handling the REJECTs and also won't reschedule.
> > 
> > The fix is to disable bottom half during the garbage collecting, as it
> > already was in the first place (most calls to it came from softirqs).
> > 
> > Signed-off-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
> > Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> > Acked-by: David S. Miller <davem@davemloft.net>
> > Cc: stable@vger.kernel.org
> 
> -stable folks, please integrate this directly, thanks!

I've appplied this and the previous two patches mentioned ('ipv4: move
route garbage collector to work queue' and 'ipv4: avoid parallel route
cache gc executions').  But I didn't get the other two from you.  The
last batch of networking fixes I received and applied was dated
2014-08-07, and the next one I've seen is dated 2014-10-11 and has
nothing for 3.2 or 3.4.  Did I miss one between these?

Ben.

-- 
Ben Hutchings
[W]e found...that it wasn't as easy to get programs right as we had thought.
... I realized that a large part of my life from then on was going to be spent
in finding mistakes in my own programs. - Maurice Wilkes, 1949

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