From: David S. Miller <davem@davemloft.net>
Date: Sun, 24 Sep 2006 01:26:24 +0000 (-0700)
Subject: SPARC64: Fix serious bug in sched_clock() on sparc64
X-Git-Tag: v2.6.17.14~8
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=47ca006812200d8cdc2745bdcadc126e5b360004;p=thirdparty%2Fkernel%2Fstable.git

SPARC64: Fix serious bug in sched_clock() on sparc64

[SPARC64]: Fix sched_clock() wrapping every ~17 seconds.

Unfortunately, sparc64 doesn't have an easy way to do a "64 X 64 -->
128" bit multiply like PowerPC and IA64 do.  We were doing a
"64 X 64 --> 64" bit multiple which causes overflow very quickly with
a 30-bit quotient shift.

So use a quotientshift count of 10 instead of 30, just like x86 and
ARM do.

This also fixes the wrapping of printk timestamp values every ~17
seconds.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/arch/sparc64/kernel/time.c b/arch/sparc64/kernel/time.c
index e55b5c6ece027..2031eda88b9f7 100644
--- a/arch/sparc64/kernel/time.c
+++ b/arch/sparc64/kernel/time.c
@@ -1105,7 +1105,7 @@ static struct time_interpolator sparc64_cpu_interpolator = {
 };
 
 /* The quotient formula is taken from the IA64 port. */
-#define SPARC64_NSEC_PER_CYC_SHIFT	30UL
+#define SPARC64_NSEC_PER_CYC_SHIFT	10UL
 void __init time_init(void)
 {
 	unsigned long clock = sparc64_init_timers();