linux-kernel - x86: udelay: Use this_cpu_read to avoid address calculation

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Date:	Thu, 16 Dec 2010 12:14:43 -0600 (CST)
From:	Christoph Lameter <cl@...ux.com>
To:	Tejun Heo <htejun@...il.com>
cc:	"H. Peter Anvin" <hpa@...or.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	akpm@...ux-foundation.org, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: x86: udelay: Use this_cpu_read to avoid address calculation

The code will use a segment prefix instead of doing the lookup and calculation.

Signed-off-by: Christoph Lameter <cl@...ux.com>

---
 arch/x86/lib/delay.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/arch/x86/lib/delay.c
===================================================================
--- linux-2.6.orig/arch/x86/lib/delay.c	2010-12-16 11:45:12.000000000 -0600
+++ linux-2.6/arch/x86/lib/delay.c	2010-12-16 11:45:37.000000000 -0600
@@ -121,7 +121,7 @@ inline void __const_udelay(unsigned long
 	asm("mull %%edx"
 		:"=d" (xloops), "=&a" (d0)
 		:"1" (xloops), "0"
-		(cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
+		(this_cpu_read(cpu_info.loops_per_jiffy) * (HZ/4)));

 	__delay(++xloops);
 }

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