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[PATCH] s390: spinlock corner case

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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 <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Heiko Carstens 2005-09-03 15:58:05 -07:00 committed by Linus Torvalds
parent c563077e52
commit 9513e5e3f5
1 changed files with 2 additions and 2 deletions
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4
include/asm-s390/spinlock.h
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@ -47,7 +47,7 @@ extern int _raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc);
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(spinlock_t *lp)
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;