From: Tejun Heo <tj@kernel.org>
Date: Sat, 28 Jun 2014 12:10:14 +0000 (-0400)
Subject: percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero()
X-Git-Tag: omap-for-v3.17/fixes-against-rc2~191^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2d7227828e1475c7b272e55bd70c4cec8eea219a;p=pandora-kernel.git

percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero()

Now that explicit invocation of percpu_ref_exit() is necessary to free
the percpu counter, we can implement percpu_ref_reinit() which
reinitializes a released percpu_ref.  This can be used implement
scalable gating switch which can be drained and then re-opened without
worrying about memory allocation failures.

percpu_ref_is_zero() is added to be used in a sanity check in
percpu_ref_exit().  As this function will be useful for other purposes
too, make it a public interface.

v2: Use smp_read_barrier_depends() instead of smp_load_acquire().  We
    only need data dep barrier and smp_load_acquire() is stronger and
    heavier on some archs.  Spotted by Lai Jiangshan.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
---

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