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Commit e0a60296 authored by Ingo Molnar's avatar Ingo Molnar Committed by Linus Torvalds
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[PATCH] Fix spinlock debugging delays to not time out too early 



The spinlock-debug wait-loop was using loops_per_jiffy to detect too long
spinlock waits - but on fast CPUs this led to a way too fast timeout and false
messages.

The fix is to include a __delay(1) call in the loop, to correctly approximate
the intended delay timeout of 1 second.  The code assumes that every
architecture implements __delay(1) to last around 1/(loops_per_jiffy*HZ)
seconds.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 8519fb30

lib/spinlock_debug.c

+3 −3
Original line number Diff line number Diff line
@@ -72,9 +72,9 @@ static void __spin_lock_debug(spinlock_t *lock) 


	for (;;) {

		for (i = 0; i < loops_per_jiffy * HZ; i++) {

			cpu_relax();

			if (__raw_spin_trylock(&lock->raw_lock))

				return;

			__delay(1);

		}

		/* lockup suspected: */

		if (print_once) {
@@ -144,9 +144,9 @@ static void __read_lock_debug(rwlock_t *lock) 


	for (;;) {

		for (i = 0; i < loops_per_jiffy * HZ; i++) {

			cpu_relax();

			if (__raw_read_trylock(&lock->raw_lock))

				return;

			__delay(1);

		}

		/* lockup suspected: */

		if (print_once) {
@@ -217,9 +217,9 @@ static void __write_lock_debug(rwlock_t *lock) 


	for (;;) {

		for (i = 0; i < loops_per_jiffy * HZ; i++) {

			cpu_relax();

			if (__raw_write_trylock(&lock->raw_lock))

				return;

			__delay(1);

		}

		/* lockup suspected: */

		if (print_once) {