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 <[email protected]>
Signed-off-by: Andi Kleen <[email protected]>
[[email protected]: !time_after() -> time_before_eq() as suggested by Jiri Slaby]
Signed-off-by: Jan Beulich <[email protected]>
Cc: Jiri Slaby <[email protected]>
Cc: Jeremy Fitzhardinge <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Tim Deegan

init/calibrate.c

@@ -66,16 +66,16 @@ 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);
 		}
 		read_current_timer(&post_start);
 
 		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);
 		}