From: Manfred Spraul <manfred@colorfullife.com>
Date: Mon, 30 Sep 2013 20:45:06 +0000 (-0700)
Subject: ipc/sem.c: optimize sem_lock()
X-Git-Tag: v3.12-rc4~35^2~17
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d07b68ce16ae9535955ba2059dedba5309c3ca1;p=pandora-kernel.git

ipc/sem.c: optimize sem_lock()

Operations that need access to the whole array must guarantee that there
are no simple operations ongoing.  Right now this is achieved by
spin_unlock_wait(sem->lock) on all semaphores.

If complex_count is nonzero, then this spin_unlock_wait() is not
necessary, because it was already performed in the past by the thread
that increased complex_count and even though sem_perm.lock was dropped
inbetween, no simple operation could have started, because simple
operations cannot start when complex_count is non-zero.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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