From 9b0fc9c09f1b262b7fe697eba6b05095d78850e5 Mon Sep 17 00:00:00 2001
From: Michel Lespinasse <walken@google.com>
Date: Tue, 7 May 2013 06:45:57 -0700
Subject: [PATCH] rwsem: skip initial trylock in rwsem_down_write_failed

We can skip the initial trylock in rwsem_down_write_failed() if there
are known active lockers already, thus saving one likely-to-fail
cmpxchg.

Signed-off-by: Michel Lespinasse <walken@google.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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