linux-kernel - [PATCH] locking/qspinlock: Use this_cpu_ptr instead of this_cpu

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Message-Id: <1464947330-3568-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
Date:	Fri,  3 Jun 2016 17:48:50 +0800
From:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...hat.com, peterz@...radead.org, waiman.long@....com,
	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Subject: [PATCH] locking/qspinlock: Use this_cpu_ptr instead of this_cpu_dec

queued_spin_lock_slowpath should not worry about interrupt change
node->count by accident because ->count is inc and dec when we
enter/leave queued_spin_lock_slowpath.

So this_cpu_dec() does some no point things here, lets use this_cpu_ptr
for a small optimization.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
 kernel/locking/qspinlock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 99f31e4..2b4daac 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -492,7 +492,7 @@ release:
 	/*
 	 * release the node
 	 */
-	this_cpu_dec(mcs_nodes[0].count);
+	this_cpu_ptr(&mcs_nodes[0])->count--;
 }
 EXPORT_SYMBOL(queued_spin_lock_slowpath);
 
-- 
1.9.1