[PATCH] spinlock_debug: don't recompute (jiffies_per_loop * HZ) in spinloop

In spinlock_debug.c, the spinloops call __delay() on every iteration.
Because that is an external function, (jiffies_per_loop * HZ), the loop's
iteration limit, gets recomputed every time.  Caching it explicitly
prevents that.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

lib/spinlock_debug.c

@@ -99,11 +99,12 @@ static inline void debug_spin_unlock(spinlock_t *lock)
 
 static void __spin_lock_debug(spinlock_t *lock)
 {
-	int print_once = 1;
 	u64 i;
+	u64 loops = loops_per_jiffy * HZ;
+	int print_once = 1;
 
 	for (;;) {
-		for (i = 0; i < loops_per_jiffy * HZ; i++) {
+		for (i = 0; i < loops; i++) {
 			if (__raw_spin_trylock(&lock->raw_lock))
 				return;
 			__delay(1);
@@ -165,11 +166,12 @@ static void rwlock_bug(rwlock_t *lock, const char *msg)
 #if 0		/* __write_lock_debug() can lock up - maybe this can too? */
 static void __read_lock_debug(rwlock_t *lock)
 {
-	int print_once = 1;
 	u64 i;
+	u64 loops = loops_per_jiffy * HZ;
+	int print_once = 1;
 
 	for (;;) {
-		for (i = 0; i < loops_per_jiffy * HZ; i++) {
+		for (i = 0; i < loops; i++) {
 			if (__raw_read_trylock(&lock->raw_lock))
 				return;
 			__delay(1);
@@ -239,11 +241,12 @@ static inline void debug_write_unlock(rwlock_t *lock)
 #if 0		/* This can cause lockups */
 static void __write_lock_debug(rwlock_t *lock)
 {
-	int print_once = 1;
 	u64 i;
+	u64 loops = loops_per_jiffy * HZ;
+	int print_once = 1;
 
 	for (;;) {
-		for (i = 0; i < loops_per_jiffy * HZ; i++) {
+		for (i = 0; i < loops; i++) {
 			if (__raw_write_trylock(&lock->raw_lock))
 				return;
 			__delay(1);