linux-kernel - [PATCH] [63/275] fix jiffy calculations in calibrate_delay

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Message-Id: <20110330210500.065CC3E1A05@tassilo.jf.intel.com>
Date:	Wed, 30 Mar 2011 14:04:59 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	Tim.Deegan@...rix.com, ak@...ux.intel.com, jbeulich@...ell.com,
	jslaby@...e.cz, jeremy@...p.org, torvalds@...ux-foundation.org,
	gregkh@...e.de, linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com
Subject: [PATCH] [63/275] fix jiffy calculations in calibrate_delay_direct to handle overflow

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Tim Deegan <Tim.Deegan@...rix.com>

commit 70a062286b9dfcbd24d2e11601aecfead5cf709a upstream.

Fixes a hang when booting as dom0 under Xen, when jiffies can be
quite large by the time the kernel init gets this far.

Signed-off-by: Tim Deegan <Tim.Deegan@...rix.com>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
[jbeulich@...ell.com: !time_after() -> time_before_eq() as suggested by Jiri Slaby]
Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Jiri Slaby <jslaby@...e.cz>
Cc: Jeremy Fitzhardinge <jeremy@...p.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 init/calibrate.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-2.6.35.y/init/calibrate.c
===================================================================
--- linux-2.6.35.y.orig/init/calibrate.c	2011-03-29 22:51:44.697579468 -0700
+++ linux-2.6.35.y/init/calibrate.c	2011-03-29 23:02:59.497313032 -0700
@@ -66,7 +66,7 @@
 		pre_start = 0;
 		read_current_timer(&start);
 		start_jiffies = jiffies;
-		while (jiffies <= (start_jiffies + 1)) {
+		while (time_before_eq(jiffies, start_jiffies + 1)) {
 			pre_start = start;
 			read_current_timer(&start);
 		}
@@ -74,8 +74,8 @@
 
 		pre_end = 0;
 		end = post_start;
-		while (jiffies <=
-		       (start_jiffies + 1 + DELAY_CALIBRATION_TICKS)) {
+		while (time_before_eq(jiffies, start_jiffies + 1 +
+					       DELAY_CALIBRATION_TICKS)) {
 			pre_end = end;
 			read_current_timer(&end);
 		}
--
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