s390/spinlock: avoid yield to non existent cpu

heicarst · Martin Schwidefsky · commit 8497695243f7 · 2016-04-15T18:01:48.000+02:00
arch_spin_lock_wait_flags() checks if a spinlock is not held before trying a compare and swap instruction. If the lock is unlocked it tries the compare and swap instruction, however if a different cpu grabbed the lock in the meantime the instruction will fail as expected. Subsequently the arch_spin_lock_wait_flags() incorrectly tries to figure out if the cpu that holds the lock is running. However it is using the wrong cpu number for this (-1) and then will also yield the current cpu to the wrong cpu. Fix this by adding a missing continue statement. Fixes: 470ada6 ("s390/spinlock: refactor arch_spin_lock_wait[_flags]") Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
@@ -105,6 +105,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
 			if (_raw_compare_and_swap(&lp->lock, 0, cpu))
 				return;
 			local_irq_restore(flags);
+			continue;
 		}
 		/* Check if the lock owner is running. */
 		if (first_diag && cpu_is_preempted(~owner)) {

Original file line number	Diff line number	Diff line change
`@@ -105,6 +105,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)`
`105`	`105`	`if (_raw_compare_and_swap(&lp->lock, 0, cpu))`
`106`	`106`	`return;`
`107`	`107`	`local_irq_restore(flags);`
	`108`	`+ continue;`
`108`	`109`	`}`
`109`	`110`	`/* Check if the lock owner is running. */`
`110`	`111`	`if (first_diag && cpu_is_preempted(~owner)) {`