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ntdll: Try to avoid an unnecessary syscall in fast_release_srw_exclusive(). 

Signed-off-by: Zebediah Figura <zfigura@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
This commit is contained in:
Zebediah Figura 2019-06-10 11:07:54 -04:00 committed by Alexandre Julliard
parent e2411ebecb
commit 07e86d3c9d
1 changed files with 11 additions and 4 deletions
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15
dlls/ntdll/sync.c
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@ -1667,7 +1667,10 @@ DWORD WINAPI RtlRunOnceExecuteOnce( RTL_RUN_ONCE *once, PRTL_RUN_ONCE_INIT_FN fu
* 30-16 - Number of exclusive waiters. Unlike the fallback implementation,
* this does not include the thread owning the lock, or shared threads
* waiting on the lock.
* 15-0 - Number of shared owners. Unlike the fallback implementation, this
* 15 - Does this lock have any shared waiters? We use this as an
* optimization to avoid unnecessary FUTEX_WAKE_BITSET calls when
* releasing an exclusive lock.
* 14-0 - Number of shared owners. Unlike the fallback implementation, this
* does not include the number of shared threads waiting on the lock.
* Thus the state [1, x, >=1] will never occur.
*/
@ -1675,7 +1678,8 @@ DWORD WINAPI RtlRunOnceExecuteOnce( RTL_RUN_ONCE *once, PRTL_RUN_ONCE_INIT_FN fu
#define SRWLOCK_FUTEX_EXCLUSIVE_LOCK_BIT 0x80000000
#define SRWLOCK_FUTEX_EXCLUSIVE_WAITERS_MASK 0x7fff0000
#define SRWLOCK_FUTEX_EXCLUSIVE_WAITERS_INC 0x00010000
#define SRWLOCK_FUTEX_SHARED_OWNERS_MASK 0x0000ffff
#define SRWLOCK_FUTEX_SHARED_WAITERS_BIT 0x00008000
#define SRWLOCK_FUTEX_SHARED_OWNERS_MASK 0x00007fff
#define SRWLOCK_FUTEX_SHARED_OWNERS_INC 0x00000001
/* Futex bitmasks; these are independent from the bits in the lock itself. */
@ -1810,7 +1814,7 @@ static NTSTATUS fast_acquire_srw_shared( RTL_SRWLOCK *lock )
}
else
{
new = old;
new = old | SRWLOCK_FUTEX_SHARED_WAITERS_BIT;
wait = TRUE;
}
} while (interlocked_cmpxchg( (int *)lock, new, old ) != old);
@ -1841,11 +1845,14 @@ static NTSTATUS fast_release_srw_exclusive( RTL_SRWLOCK *lock )
}
new = old & ~SRWLOCK_FUTEX_EXCLUSIVE_LOCK_BIT;
if (!(new & SRWLOCK_FUTEX_EXCLUSIVE_WAITERS_MASK))
new &= ~SRWLOCK_FUTEX_SHARED_WAITERS_BIT;
} while (interlocked_cmpxchg( (int *)lock, new, old ) != old);
if (new & SRWLOCK_FUTEX_EXCLUSIVE_WAITERS_MASK)
futex_wake_bitset( (int *)lock, 1, SRWLOCK_FUTEX_BITSET_EXCLUSIVE );
else
else if (old & SRWLOCK_FUTEX_SHARED_WAITERS_BIT)
futex_wake_bitset( (int *)lock, INT_MAX, SRWLOCK_FUTEX_BITSET_SHARED );
return STATUS_SUCCESS;