From: Michel Lespinasse <walken@google.com>
Date: Tue, 7 May 2013 13:45:50 +0000 (-0700)
Subject: rwsem: shorter spinlocked section in rwsem_down_failed_common()
X-Git-Tag: omap-for-v3.10/dt-fixes-for-merge-window~14^2~12
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f7dd1cee9a4e2b1450e4a3732636dfbf28562ee4;p=pandora-kernel.git

rwsem: shorter spinlocked section in rwsem_down_failed_common()

This change reduces the size of the spinlocked and TASK_UNINTERRUPTIBLE
sections in rwsem_down_failed_common():

- We only need the sem->wait_lock to insert ourselves on the wait_list;
  the waiter node can be prepared outside of the wait_lock.

- The task state only needs to be set to TASK_UNINTERRUPTIBLE immediately
  before checking if we actually need to sleep; it doesn't need to protect
  the entire function.

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