fix jiffy calculations in calibrate_delay_direct to handle overflow

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: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/init/calibrate.c b/init/calibrate.c
index 6eb48e53d61c58869bdc8aa5250397a2594ab0e3..24fe022c55f976004c7acfb1c22ed6b7f0ce0954 100644 (file)
--- 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);
                }