From c59d2989479d6431f4e83e2829c6cf25fc3f1184 Mon Sep 17 00:00:00 2001
From: Sumit Singh <sumsingh@nvidia.com>
Date: Mon, 21 Apr 2014 11:09:58 +0530
Subject: smp: enhance power efficiency

Here we are trying to reduce power usage through the
use of macros cpu_relaxed_read_short and cpu_relaxed_read.

Bug 1440421

Change-Id: I114d122cf58b1cf7b93b4b5f5d712360a2f1e096
Signed-off-by: Sumit Singh <sumsingh@nvidia.com>
Reviewed-on: http://git-master/r/425947
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Sri Krishna Chowdary <schowdary@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Alexander Van Brunt <avanbrunt@nvidia.com>
---
 kernel/smp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/smp.c b/kernel/smp.c
index 5221ac677e60..1acf2bd32dbe 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -2,6 +2,7 @@
  * Generic helpers for smp ipi calls
  *
  * (C) Jens Axboe <jens.axboe@oracle.com> 2008
+ * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
  */
 #include <linux/rcupdate.h>
 #include <linux/rculist.h>
@@ -12,6 +13,7 @@
 #include <linux/gfp.h>
 #include <linux/smp.h>
 #include <linux/cpu.h>
+#include <asm/relaxed.h>
 
 #include "smpboot.h"
 
@@ -101,8 +103,8 @@ void __init call_function_init(void)
  */
 static void csd_lock_wait(struct call_single_data *csd)
 {
-	while (csd->flags & CSD_FLAG_LOCK)
-		cpu_relax();
+	while (cpu_relaxed_read_short(&csd->flags) & CSD_FLAG_LOCK)
+		cpu_read_relax();
 }
 
 static void csd_lock(struct call_single_data *csd)
-- 
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