tree d97aab24d8d0abbd8378e7c851f7a55d266bb851
parent e657e078d3dfa9f96976db7a2b5fd7d7c9f1f1a6
author Mikulas Patocka <mpatocka@redhat.com> 1350949067 -0400
committer Linus Torvalds <torvalds@linux-foundation.org> 1351447176 -0700

percpu-rw-semaphores: use light/heavy barriers

This patch introduces new barrier pair light_mb() and heavy_mb() for
percpu rw semaphores.

This patch fixes a bug in percpu-rw-semaphores where a barrier was
missing in percpu_up_write.

This patch improves performance on the read path of
percpu-rw-semaphores: on non-x86 cpus, there was a smp_mb() in
percpu_up_read. This patch changes it to a compiler barrier and removes
the "#if defined(X86) ..." condition.

From: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>