From: Thomas Hellstrom <thellstrom@vmware.com>
Date: Tue, 6 Nov 2012 11:31:51 +0000 (+0000)
Subject: drm/ttm: Optimize reservation slightly
X-Git-Tag: v3.8-rc1~82^2~147
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6c1e963cc5771c93d4ed7aa8bdd4322a7c918e9b;p=pandora-kernel.git

drm/ttm: Optimize reservation slightly

Reservation locking currently always takes place under the LRU spinlock.
Hence, strictly there is no need for an atomic_cmpxchg call; we can use
atomic_read followed by atomic_write since nobody else will ever reserve
without the lru spinlock held.
At least on Intel this should remove a locked bus cycle on successful
reserve.

Note that thit commit may be obsoleted by the cross-device reservation work.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
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