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s390/rwlock: use the interlocked-access facility 1 instructions

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Make use of the load-and-add, load-and-or and load-and-and instructions
to atomically update the read-write lock without a compare-and-swap loop.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2014-09-22 16:34:38 +02:00
parent 94232a4332
commit bbae71bf9c
2 changed files with 108 additions and 2 deletions
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76
arch/s390/include/asm/spinlock.h
View file

@ -130,8 +130,6 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
*/
#define arch_write_can_lock(x) ((x)->lock == 0)
extern void _raw_read_lock_wait(arch_rwlock_t *lp);
extern void _raw_write_lock_wait(arch_rwlock_t *lp);
extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
@ -152,6 +150,78 @@ static inline int arch_write_trylock_once(arch_rwlock_t *rw)
_raw_compare_and_swap(&rw->lock, 0, 0x80000000));
}
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
#define __RAW_OP_OR "lao"
#define __RAW_OP_AND "lan"
#define __RAW_OP_ADD "laa"
#define __RAW_LOCK(ptr, op_val, op_string) \
({ \
unsigned int old_val; \
\
typecheck(unsigned int *, ptr); \
asm volatile( \
op_string " %0,%2,%1\n" \
"bcr 14,0\n" \
: "=d" (old_val), "+Q" (*ptr) \
: "d" (op_val) \
: "cc", "memory"); \
old_val; \
})
#define __RAW_UNLOCK(ptr, op_val, op_string) \
({ \
unsigned int old_val; \
\
typecheck(unsigned int *, ptr); \
asm volatile( \
"bcr 14,0\n" \
op_string " %0,%2,%1\n" \
: "=d" (old_val), "+Q" (*ptr) \
: "d" (op_val) \
: "cc", "memory"); \
old_val; \
})
extern void _raw_read_lock_wait(arch_rwlock_t *lp);
extern void _raw_write_lock_wait(arch_rwlock_t *lp, unsigned int prev);
static inline void arch_read_lock(arch_rwlock_t *rw)
{
unsigned int old;
old = __RAW_LOCK(&rw->lock, 1, __RAW_OP_ADD);
if ((int) old < 0)
_raw_read_lock_wait(rw);
}
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
__RAW_UNLOCK(&rw->lock, -1, __RAW_OP_ADD);
}
static inline void arch_write_lock(arch_rwlock_t *rw)
{
unsigned int old;
old = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
if (old != 0)
_raw_write_lock_wait(rw, old);
rw->owner = SPINLOCK_LOCKVAL;
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
rw->owner = 0;
__RAW_UNLOCK(&rw->lock, 0x7fffffff, __RAW_OP_AND);
}
#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
extern void _raw_read_lock_wait(arch_rwlock_t *lp);
extern void _raw_write_lock_wait(arch_rwlock_t *lp);
static inline void arch_read_lock(arch_rwlock_t *rw)
{
if (!arch_read_trylock_once(rw))
@ -187,6 +257,8 @@ static inline void arch_write_unlock(arch_rwlock_t *rw)
: "cc", "memory");
}
#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
if (!arch_read_trylock_once(rw))

34
arch/s390/lib/spinlock.c
View file

@ -114,6 +114,9 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
unsigned int owner, old;
int count = spin_retry;
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
__RAW_LOCK(&rw->lock, -1, __RAW_OP_ADD);
#endif
owner = 0;
while (1) {
if (count-- <= 0) {
@ -147,6 +150,35 @@ int _raw_read_trylock_retry(arch_rwlock_t *rw)
}
EXPORT_SYMBOL(_raw_read_trylock_retry);
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
{
unsigned int owner, old;
int count = spin_retry;
owner = 0;
while (1) {
if (count-- <= 0) {
if (owner && !smp_vcpu_scheduled(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
owner = ACCESS_ONCE(rw->owner);
smp_rmb();
if ((int) old >= 0) {
prev = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
old = prev;
}
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
break;
}
}
EXPORT_SYMBOL(_raw_write_lock_wait);
#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
void _raw_write_lock_wait(arch_rwlock_t *rw)
{
unsigned int owner, old, prev;
@ -173,6 +205,8 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
}
EXPORT_SYMBOL(_raw_write_lock_wait);
#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
int _raw_write_trylock_retry(arch_rwlock_t *rw)
{
unsigned int old;