From: Eric Dumazet <edumazet@google.com>
Date: Fri, 24 Aug 2012 05:40:47 +0000 (+0000)
Subject: ipv4: take rt_uncached_lock only if needed
X-Git-Tag: v3.6-rc5~20^2~25
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78df76a065ae3b5dbcb9a29912adc02f697de498;p=pandora-kernel.git

ipv4: take rt_uncached_lock only if needed

Multicast traffic allocates dst with DST_NOCACHE, but dst is
not inserted into rt_uncached_list.

This slowdown multicast workloads on SMP because rt_uncached_lock is
contended.

Change the test before taking the lock to actually check the dst
was inserted into rt_uncached_list.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

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