linux-kernel - [PATCH v2] locking/qspinlock: Use __this_cpu

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Message-Id: <1465886247-3773-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
Date:	Tue, 14 Jun 2016 14:37:27 +0800
From:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	peterz@...radead.org, mingo@...hat.com, Waiman.Long@....com,
	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Subject: [PATCH v2] locking/qspinlock: Use __this_cpu_dec instead

queued_spin_lock_slowpath should not worry about another
queued_spin_lock_slowpath which runs in interrupt changes node->count by
accident because node->count keeps the same value everytime we
enter/leave queued_spin_lock_slowpath.

On some archs this_cpu_dec will save/restore irq flags, this will give a
heavy work load. Lets use __this_cpu_dec instead.

Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
---
change from v1:
	replace this_cpu_ptr with __this_cpu_dec
---
 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..9fd1a1e 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_dec(mcs_nodes[0].count);
 }
 EXPORT_SYMBOL(queued_spin_lock_slowpath);
 
-- 
1.9.1