linux-kernel - [PATCH 1/8] srcu: simplify __srcu_read_unlock() via this_cpu

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Message-Id: <1354178770-6028-2-git-send-email-laijs@cn.fujitsu.com>
Date:	Thu, 29 Nov 2012 16:46:02 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH 1/8] srcu: simplify __srcu_read_unlock() via this_cpu_dec()

this_cpu_dec() can do the same thing and sometimes it is better.
(avoid preempt_disable() and use more tiny instructions)

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
 kernel/srcu.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/srcu.c b/kernel/srcu.c
index b363b09..b2e4f36 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -317,10 +317,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
  */
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {
-	preempt_disable();
 	smp_mb(); /* C */  /* Avoid leaking the critical section. */
-	ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
-	preempt_enable();
+	this_cpu_dec(sp->per_cpu_ref->c[idx]);
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock);
 
-- 
1.7.4.4

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