linux-kernel - [34-longterm 059/247] fix jiffy calculations in calibrate_delay

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Date:	Thu, 23 Jun 2011 13:25:58 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Tim Deegan <Tim.Deegan@...rix.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 059/247] fix jiffy calculations in calibrate_delay_direct to handle overflow

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

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

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>
[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: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 init/calibrate.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/init/calibrate.c b/init/calibrate.c
index 6eb48e5..24fe022 100644
--- a/init/calibrate.c
+++ b/init/calibrate.c
@@ -66,7 +66,7 @@ static unsigned long __cpuinit calibrate_delay_direct(void)
 		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 @@ static unsigned long __cpuinit calibrate_delay_direct(void)
 
 		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);
 		}
-- 
1.7.4.4

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