[34-longterm 059/247] fix jiffy calculations in calibrate_delay_direct to handle overflow

Paul Gortmaker
2011-06-23T17:31:24Z

From: Tim Deegan <Tim.Deegan@citrix.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@citrix.com>
[jbeulich@novell.com: !time_after() -> time_before_eq() as suggested by Jiri Slaby]
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.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