fix jiffy calculations in calibrate_delay_direct to handle overflow
Tim Deegan [Thu, 10 Feb 2011 08:50:41 +0000 (08:50 +0000)]
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>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/calibrate.c

index 6eb48e5..24fe022 100644 (file)
@@ -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);
                }