Message-Id: <20101206174017.684979312@linux.com>
User-Agent: quilt/0.48-1
Date: Mon, 06 Dec 2010 11:40:06 -0600
From: Christoph Lameter <cl@linux.com>
To: Tejun Heo <tj@kernel.org>
Cc: akpm@linux-foundation.org, Richard Kennedy <richard@rsk.demon.co.uk>,
        Matt Mackall <mpm@selenic.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: linux-kernel@vger.kernel.org
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: [cpuops inc_return V1 8/9] random: Use this_cpu_inc_return
References: <20101206173958.685460926@linux.com>
Content-Disposition: inline; filename=cpuops_inc_return_random
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1151
Lines: 30

__this_cpu_inc can create a single instruction to do the same as
__get_cpu_var()++.

Cc: Richard Kennedy <richard@rsk.demon.co.uk>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Christoph Lameter <cl@linux.com>

---
 drivers/char/random.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/drivers/char/random.c
===================================================================
--- linux-2.6.orig/drivers/char/random.c	2010-12-06 11:01:06.000000000 -0600
+++ linux-2.6/drivers/char/random.c	2010-12-06 11:19:38.000000000 -0600
@@ -626,7 +626,7 @@ static void add_timer_randomness(struct
 	preempt_disable();
 	/* if over the trickle threshold, use only 1 in 4096 samples */
 	if (input_pool.entropy_count > trickle_thresh &&
-	    (__get_cpu_var(trickle_count)++ & 0xfff))
+	    ((__this_cpu_inc_return(trickle_count) - 1) & 0xfff))
 		goto out;
 
 	sample.jiffies = jiffies;

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