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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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34
arch/s390/lib/spinlock.c
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@@ -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;