From: Heiko Carstens On s390 the lock value used for spinlocks consists of the lower 32 bits of the PSW that holds the lock. If this address happens to be on a four gigabyte boundary the lock is left unlocked. This allows other cpus to grab the same lock and enter a lock protected code path concurrently. In theory this can happen if the vmalloc area for the code of a module crosses a 4 GB boundary. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Andrew Morton --- include/asm-s390/spinlock.h | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff -puN include/asm-s390/spinlock.h~s390-spinlock-corner-case include/asm-s390/spinlock.h --- devel/include/asm-s390/spinlock.h~s390-spinlock-corner-case 2005-08-29 23:58:37.000000000 -0700 +++ devel-akpm/include/asm-s390/spinlock.h 2005-08-29 23:58:37.000000000 -0700 @@ -47,7 +47,7 @@ extern int _raw_spin_trylock_retry(spinl static inline void _raw_spin_lock(spinlock_t *lp) { - unsigned long pc = (unsigned long) __builtin_return_address(0); + unsigned long pc = 1 | (unsigned long) __builtin_return_address(0); if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0)) _raw_spin_lock_wait(lp, pc); @@ -55,7 +55,7 @@ static inline void _raw_spin_lock(spinlo static inline int _raw_spin_trylock(spinlock_t *lp) { - unsigned long pc = (unsigned long) __builtin_return_address(0); + unsigned long pc = 1 | (unsigned long) __builtin_return_address(0); if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0)) return 1; _