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MDEV-14529 - InnoDB rw-locks: optimize memory barriers

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Relax memory barrier for waiters: these 2 stores must be completed before
os_event_set() finishes. This is guaranteed by RELEASE barrier issued by
mutex.exit() of os_event_set().
This commit is contained in:
Sergey Vojtovich 2017-12-01 13:52:24 +04:00
parent 5b624f00fc
commit 51bb18f989
1 changed files with 4 additions and 2 deletions
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6
storage/innobase/include/sync0rw.ic
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@ -420,7 +420,8 @@ rw_lock_x_unlock_func(
exist when there is a writer. */
if (my_atomic_load32_explicit(&lock->waiters,
MY_MEMORY_ORDER_RELAXED)) {
my_atomic_store32((int32*) &lock->waiters, 0);
my_atomic_store32_explicit(&lock->waiters, 0,
MY_MEMORY_ORDER_RELAXED);
os_event_set(lock->event);
sync_array_object_signalled();
}
@ -474,7 +475,8 @@ rw_lock_sx_unlock_func(
holder. */
if (my_atomic_load32_explicit(&lock->waiters,
MY_MEMORY_ORDER_RELAXED)) {
my_atomic_store32((int32*) &lock->waiters, 0);
my_atomic_store32_explicit(&lock->waiters, 0,
MY_MEMORY_ORDER_RELAXED);
os_event_set(lock->event);
sync_array_object_signalled();
}