Module: wine Branch: master Commit: 07e86d3c9df23ea18166ff89503d1dc02d1bda36 URL: https://source.winehq.org/git/wine.git/?a=commit;h=07e86d3c9df23ea18166ff895...
Author: Zebediah Figura zfigura@codeweavers.com Date: Mon Jun 10 11:07:54 2019 -0400
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
---
dlls/ntdll/sync.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c index c7a96b6..35b89df 100644 --- a/dlls/ntdll/sync.c +++ b/dlls/ntdll/sync.c @@ -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;