From: Yuxuan Shui yshui@codeweavers.com
--- dlls/kernel32/tests/sync.c | 24 ++ dlls/ntdll/sync.c | 623 ++++++++++++++++++++++++++++--------- 2 files changed, 504 insertions(+), 143 deletions(-)
diff --git a/dlls/kernel32/tests/sync.c b/dlls/kernel32/tests/sync.c index 60180194b7a..4eaec87c52f 100644 --- a/dlls/kernel32/tests/sync.c +++ b/dlls/kernel32/tests/sync.c @@ -2533,6 +2533,29 @@ static void test_srwlock_example(void) trace("number of total exclusive accesses is %ld\n", srwlock_protected_value); }
+static void test_srwlock_quirk(void) +{ + union { SRWLOCK *s; LONG *l; } u = { &srwlock_example }; + + if (!pInitializeSRWLock) { + /* function is not yet in XP, only in newer Windows */ + win_skip("no srw lock support.\n"); + return; + } + + *u.l = 0; + pReleaseSRWLockExclusive(&srwlock_example); + ok(*u.l == 0xffffffff, "expected 0xffffffff, got %lx\n", *u.l); + + *u.l = 1; + pReleaseSRWLockExclusive(&srwlock_example); + ok(*u.l == 0, "expected 0x0, got %lx\n", *u.l); + + *u.l = 0x10000; + pReleaseSRWLockExclusive(&srwlock_example); + ok(*u.l == 0xffff, "expected 0xffff, got %lx\n", *u.l); +} + static DWORD WINAPI alertable_wait_thread(void *param) { HANDLE *semaphores = param; @@ -2887,6 +2910,7 @@ START_TEST(sync) test_srwlock_base(&aligned_srwlock); test_srwlock_base(&unaligned_srwlock.lock); test_srwlock_example(); + test_srwlock_quirk(); test_alertable_wait(); test_apc_deadlock(); test_crit_section(); diff --git a/dlls/ntdll/sync.c b/dlls/ntdll/sync.c index fa64917029a..2d1ca822ecf 100644 --- a/dlls/ntdll/sync.c +++ b/dlls/ntdll/sync.c @@ -26,6 +26,8 @@ #include <stdarg.h> #include <stdio.h> #include <stdlib.h> +#include <stdint.h> +#include <assert.h> #include <time.h>
#include "ntstatus.h" @@ -471,24 +473,95 @@ DWORD WINAPI RtlRunOnceExecuteOnce( RTL_RUN_ONCE *once, PRTL_RUN_ONCE_INIT_FN fu return RtlRunOnceComplete( once, 0, context ? *context : NULL ); }
-struct srw_lock -{ - short exclusive_waiters; +/** + * The SRWLOCK is a tagged pointer, with the last 4 bits been the tag. + * The pointer part serves 2 roles: if there is no waiters on the lock, + * it counts the number of shared owners of the lock; otherwise, it + * points to the end of the waiter queue, which is a linked list of waiters. + * This also implies the pointer must be 16 byte aligned. + * + * There are a couple helper functions below to make accessing different parts + * of the SRWLOCK easier. + */
- /* Number of shared owners, or -1 if owned exclusive. - * - * Sadly Windows has no equivalent to FUTEX_WAIT_BITSET, so in order to wake - * up *only* exclusive or *only* shared waiters (and thus avoid spurious - * wakeups), we need to wait on two different addresses. - * RtlAcquireSRWLockShared() needs to know the values of "exclusive_waiters" - * and "owners", but RtlAcquireSRWLockExclusive() only needs to know the - * value of "owners", so the former can wait on the entire structure, and - * the latter waits only on the "owners" member. Note then that "owners" - * must not be the first element in the structure. +enum srwlock_tag { + SRWLOCK_TAG_LOCKED = 1 << 0, + SRWLOCK_TAG_HAS_WAITERS = 1 << 1, + /* Unknown purpose on Windows, but we use it to indicate the list + * is being modified. */ + SRWLOCK_TAG_LIST_LOCKED = 1 << 2, + /* Unclear purpose on Windows, might be indicating this lock has + * > 1 owners. */ + SRWLOCK_TAG_HAS_MULTIPLE_OWNERS = 1 << 3, +}; + +enum srwlock_waiter_state { + SRWLOCK_WAITER_STATE_IS_EXCLUSIVE = 1, + /* ???? = 2, */ + SRWLOCK_WAITER_STATE_NOTIFIED = 1 << 2, +}; +struct DECLSPEC_ALIGN(16) srwlock_waiter { + /* Note the prev pointer is uninitialized for the list head. */ + struct srwlock_waiter *prev; + struct srwlock_waiter *head; + struct srwlock_waiter *next; + ULONG_PTR thread_id; + /* When the first waiter appears, the shared owner counter store in + * SRWLOCK is transferred here, however only the lower 28 bits are kept. + * A special value 0xffffffff indicates this waiter is not at the + * head of the list, and 0xfffffffe indicates this waiter is at the head + * of the list, but the lock is held exclusively. */ - short owners; + DWORD num_owners; + + /* A bitflag of states, see `enum srwlock_waiter_state`. */ + DWORD state; }; -C_ASSERT( sizeof(struct srw_lock) == 4 ); + +#define SRWLOCK_WAITER_IS_NOT_HEAD 0xffffffff +#define SRWLOCK_WAITER_EXCLUSIVELY_LOCKED 0xfffffffe + +#ifdef _WIN64 +#define InterlockedAddPointer(ptr,val) (PVOID)InterlockedAdd64((PLONGLONG)(ptr),(LONGLONG)(val)) +#define InterlockedAndPointer(ptr,val) (PVOID)InterlockedAnd64((PLONGLONG)(ptr),(LONGLONG)(val)) +#define InterlockedOrPointer(ptr,val) (PVOID)InterlockedOr64((PLONGLONG)(ptr),(LONGLONG)(val)) +#else +#define InterlockedAddPointer(ptr,val) (PVOID)InterlockedAdd((PLONG)(ptr),(LONG)(val)) +#define InterlockedAndPointer(ptr,val) (PVOID)InterlockedAnd((PLONG)(ptr),(LONG)(val)) +#define InterlockedOrPointer(ptr,val) (PVOID)InterlockedOr((PLONG)(ptr),(LONG)(val)) +#endif + +static inline struct srwlock_waiter *srwlock_get_waiter(RTL_SRWLOCK lock) +{ + ULONG_PTR ptr = (ULONG_PTR)lock.Ptr; + return (void *)(ptr & ~(ULONG_PTR)0xf); +} + +static inline ULONG_PTR srwlock_get_shared_count(RTL_SRWLOCK lock) +{ + ULONG_PTR ptr = (ULONG_PTR)lock.Ptr; + return ((ptr & (ULONG_PTR)0xfffffff0) >> 4); +} + +static inline USHORT srwlock_get_tag(RTL_SRWLOCK lock) +{ + ULONG_PTR ptr = (ULONG_PTR)lock.Ptr; + return (USHORT)(ptr & (ULONG_PTR)0xf); +} + +static inline RTL_SRWLOCK srwlock_from_waiter(struct srwlock_waiter *waiter, USHORT tag) +{ + RTL_SRWLOCK lock; + lock.Ptr = (void *)((ULONG_PTR)waiter | (ULONG_PTR)tag); + return lock; +} + +static inline RTL_SRWLOCK srwlock_from_shared_owner_count(ULONG_PTR count, USHORT tag) +{ + RTL_SRWLOCK lock; + lock.Ptr = (void *)(((ULONG_PTR)count << 4) | (ULONG_PTR)tag); + return lock; +}
/*********************************************************************** * RtlInitializeSRWLock (NTDLL.@) @@ -496,141 +569,218 @@ C_ASSERT( sizeof(struct srw_lock) == 4 ); * NOTES * Please note that SRWLocks do not keep track of the owner of a lock. * It doesn't make any difference which thread for example unlocks an - * SRWLock (see corresponding tests). This implementation uses two - * keyed events (one for the exclusive waiters and one for the shared - * waiters) and is limited to 2^15-1 waiting threads. + * SRWLock (see corresponding tests). */ void WINAPI RtlInitializeSRWLock( RTL_SRWLOCK *lock ) { lock->Ptr = NULL; }
-/*********************************************************************** - * RtlAcquireSRWLockExclusive (NTDLL.@) +/* Lock the SRWLOCK, remove then wake up the waiters at the front of the list, + * Only one thread can call this function at any given time. Must be called + * with LIST_LOCKED, and HAS_WAITERS bits set; the HAS_MULTIPLE_OWNERS bit + * must NOT be set. * - * NOTES - * Unlike RtlAcquireResourceExclusive this function doesn't allow - * nested calls from the same thread. "Upgrading" a shared access lock - * to an exclusive access lock also doesn't seem to be supported. - */ -void WINAPI RtlAcquireSRWLockExclusive( RTL_SRWLOCK *lock ) + * Returns TRUE if the operation is successful. If another thread acquired the + * lock while we are scanning the list, this aborts and returns FALSE. */ +static void srwlock_wake(RTL_SRWLOCK *lock, struct srwlock_waiter * const last) { - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; + RTL_SRWLOCK new, read; + struct srwlock_waiter *head = last->head, *new_head = NULL, *i; + UINT tag; + RTL_SRWLOCK expected = srwlock_from_waiter(last, + SRWLOCK_TAG_LIST_LOCKED | SRWLOCK_TAG_HAS_WAITERS); + ULONG shared_owner_count = 0;
- InterlockedIncrement16( &u.s->exclusive_waiters ); + TRACE("%p\n", lock);
- for (;;) - { - union { struct srw_lock s; LONG l; } old, new; - BOOL wait; +retry:
- do + head->num_owners = 0; + shared_owner_count = 0; + if (head->state & SRWLOCK_WAITER_STATE_IS_EXCLUSIVE) + { + new_head = head->next; + } + else + { + i = head; + while (i && !(i->state & SRWLOCK_WAITER_STATE_IS_EXCLUSIVE)) { - old.s = *u.s; - new.s = old.s; + shared_owner_count += 1; + new_head = i->next; + i = i->next; + } + if (!i) + new_head = NULL; + } + for (i = new_head; i; i = i->next) + i->head = new_head; + + tag = SRWLOCK_TAG_LOCKED; + if (shared_owner_count > 1) + tag |= SRWLOCK_TAG_HAS_MULTIPLE_OWNERS; + if (new_head == NULL) + new = srwlock_from_shared_owner_count(shared_owner_count, tag); + else + { + new = srwlock_from_waiter(last, tag | SRWLOCK_TAG_HAS_WAITERS); + if (shared_owner_count) + new_head->num_owners = shared_owner_count; + else + new_head->num_owners = SRWLOCK_WAITER_EXCLUSIVELY_LOCKED; + }
- if (!old.s.owners) - { - /* Not locked exclusive or shared. We can try to grab it. */ - new.s.owners = -1; - --new.s.exclusive_waiters; - wait = FALSE; - } - else - { - wait = TRUE; - } - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l); + TRACE("new = %p, #owners = %ld\n", new.Ptr, shared_owner_count); + read.Ptr = InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, expected.Ptr); + if (read.Ptr != expected.Ptr) + { + tag = srwlock_get_tag(read); + TRACE("bail, read = %p\n", read.Ptr); + assert(tag == (SRWLOCK_TAG_LOCKED | SRWLOCK_TAG_LIST_LOCKED | SRWLOCK_TAG_HAS_WAITERS)); + /* Bail, we need to restore the head pointers to their original value. */ + for (i = new_head; i; i = i->next) + i->head = head; + if (new_head) + new_head->num_owners = SRWLOCK_WAITER_IS_NOT_HEAD; + head->num_owners = 1; + new.Ptr = (PVOID)((ULONG_PTR)read.Ptr & ~(ULONG_PTR)SRWLOCK_TAG_LIST_LOCKED); + if (InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, read.Ptr) != read.Ptr) + goto retry; + + RtlWakeAddressSingle(&lock->Ptr); + return; + } + RtlWakeAddressSingle(&lock->Ptr);
- if (!wait) return; - RtlWaitOnAddress( &u.s->owners, &new.s.owners, sizeof(short), NULL ); + while (head != new_head) + { + /* waking up the waiter will invalidate the waiter's entry in + * the list. */ + struct srwlock_waiter *next = head->next; + InterlockedOr((LONG *)&head->state, SRWLOCK_WAITER_STATE_NOTIFIED); + TRACE("waking %p\n", head); + RtlWakeAddressSingle(&head->state); + head = next; } }
-/*********************************************************************** - * RtlAcquireSRWLockShared (NTDLL.@) +/** + * Add a new waiter to the SRWLOCK, and wait on it. The wait will be interrupted + * if the value stored in `lock` changes to something other than `expected`. * - * NOTES - * Do not call this function recursively - it will only succeed when - * there are no threads waiting for an exclusive lock! + * Returns TRUE if the lock is acquired, FALSE otherwise. */ -void WINAPI RtlAcquireSRWLockShared( RTL_SRWLOCK *lock ) +#ifdef __GNUC__ +__attribute__((force_align_arg_pointer)) +#endif +static BOOLEAN srwlock_wait(RTL_SRWLOCK *lock, DWORD waiter_state, + RTL_SRWLOCK expected) { - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; + RTL_SRWLOCK new, old; + USHORT tag; + struct srwlock_waiter *prev = NULL, waiter = {0};
- for (;;) - { - union { struct srw_lock s; LONG l; } old, new; - BOOL wait; + tag = srwlock_get_tag(expected); + TRACE("%p %p %p\n", lock, &waiter, expected.Ptr);
- do - { - old.s = *u.s; - new = old; - - if (old.s.owners != -1 && !old.s.exclusive_waiters) - { - /* Not locked exclusive, and no exclusive waiters. - * We can try to grab it. */ - ++new.s.owners; - wait = FALSE; - } - else - { - wait = TRUE; - } - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l); + if (tag & SRWLOCK_TAG_LIST_LOCKED) { + /* We only ever blocking wait on &lock->Ptr for the LIST_LOCKED bit. */ + RtlWaitOnAddress(&lock->Ptr, &expected.Ptr, sizeof(expected.Ptr), NULL); + return FALSE; + }
- if (!wait) return; - RtlWaitOnAddress( u.s, &new.s, sizeof(struct srw_lock), NULL ); + waiter.state = waiter_state; + if (tag & SRWLOCK_TAG_HAS_WAITERS) + { + prev = srwlock_get_waiter(expected); + waiter.head = NULL; + waiter.prev = prev; + waiter.num_owners = SRWLOCK_WAITER_IS_NOT_HEAD; } -} + else + { + waiter.head = &waiter; + waiter.num_owners = srwlock_get_shared_count(expected); + if (waiter.num_owners > 1) + tag |= SRWLOCK_TAG_HAS_MULTIPLE_OWNERS; + if (waiter.num_owners == 0) + waiter.num_owners = SRWLOCK_WAITER_EXCLUSIVELY_LOCKED; + tag |= SRWLOCK_TAG_HAS_WAITERS; + } + waiter.next = NULL;
-/*********************************************************************** - * RtlReleaseSRWLockExclusive (NTDLL.@) - */ -void WINAPI RtlReleaseSRWLockExclusive( RTL_SRWLOCK *lock ) -{ - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; - union { struct srw_lock s; LONG l; } old, new; + new = srwlock_from_waiter(&waiter, tag | SRWLOCK_TAG_LIST_LOCKED); + if (InterlockedCompareExchangePointer((void **)&lock->Ptr, new.Ptr, expected.Ptr) != expected.Ptr) + return FALSE;
- do - { - old.s = *u.s; - new = old; + /* The linked list is locked by us now */ + if (prev) { + WritePointerNoFence((void **)&waiter.head, prev->head); + prev->next = &waiter; + } + + /* Update tail and unlock list */ + do { + old.Ptr = ReadPointerAcquire(&lock->Ptr); + tag = srwlock_get_tag(old);
- if (old.s.owners != -1) ERR("Lock %p is not owned exclusive!\n", lock); + if (tag & (SRWLOCK_TAG_LOCKED | SRWLOCK_TAG_HAS_MULTIPLE_OWNERS)) + /* If the lock is unlocked while we are holding the list lock, + * then we would have to perform the waking up duty, so we + * would still need the list lock, otherwise we can unlock + * the list. */ + tag &= ~SRWLOCK_TAG_LIST_LOCKED;
- new.s.owners = 0; - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l); + new = srwlock_from_waiter(&waiter, tag); + TRACE("new = %p, tag = %x\n", new.Ptr, tag); + } while( InterlockedCompareExchangePointer((void **)&lock->Ptr, new.Ptr, old.Ptr) != old.Ptr );
- if (new.s.exclusive_waiters) - RtlWakeAddressSingle( &u.s->owners ); + if (!(tag & (SRWLOCK_TAG_LOCKED | SRWLOCK_TAG_HAS_MULTIPLE_OWNERS))) + srwlock_wake(lock, srwlock_get_waiter(old)); else - RtlWakeAddressAll( u.s ); + RtlWakeAddressSingle(&lock->Ptr); + + TRACE("waiting: %p, %p, %lu\n", lock, &waiter, waiter.num_owners); + while (TRUE) + { + waiter_state = ReadAcquire((LONG *)&waiter.state); + if (waiter_state & SRWLOCK_WAITER_STATE_NOTIFIED) + break; + RtlWaitOnAddress(&waiter.state, &waiter_state, sizeof(DWORD), NULL); + }; + + TRACE("acquired: %p\n", lock); + return TRUE; }
-/*********************************************************************** - * RtlReleaseSRWLockShared (NTDLL.@) - */ -void WINAPI RtlReleaseSRWLockShared( RTL_SRWLOCK *lock ) +static BOOLEAN srwlock_try_acquire_exclusive(RTL_SRWLOCK *lock, RTL_SRWLOCK *old) { - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; - union { struct srw_lock s; LONG l; } old, new; + RTL_SRWLOCK new; + USHORT tag; + struct srwlock_waiter *last;
do { - old.s = *u.s; - new = old; - - if (old.s.owners == -1) ERR("Lock %p is owned exclusive!\n", lock); - else if (!old.s.owners) ERR("Lock %p is not owned shared!\n", lock); - - --new.s.owners; - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l); + old->Ptr = ReadPointerAcquire(&lock->Ptr); + TRACE("old = %p\n", old->Ptr); + tag = srwlock_get_tag(*old); + last = srwlock_get_waiter(*old); + + /* We can't acquire the lock if it's locked (obviously), or if + * the MULTIPLE_OWNERS bit is set. See `RtlReleaseSRWLockShared` + * for an explanation on why this is necessary. */ + if (tag & (SRWLOCK_TAG_HAS_MULTIPLE_OWNERS | SRWLOCK_TAG_LOCKED)) + return FALSE; + + if (tag & SRWLOCK_TAG_HAS_WAITERS) + new = srwlock_from_waiter(last, tag | SRWLOCK_TAG_LOCKED); + else + new = srwlock_from_shared_owner_count(0, tag | SRWLOCK_TAG_LOCKED); + } while (InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, + old->Ptr ) != old->Ptr);
- if (!new.s.owners) - RtlWakeAddressSingle( &u.s->owners ); + return TRUE; }
/*********************************************************************** @@ -642,28 +792,61 @@ void WINAPI RtlReleaseSRWLockShared( RTL_SRWLOCK *lock ) */ BOOLEAN WINAPI RtlTryAcquireSRWLockExclusive( RTL_SRWLOCK *lock ) { - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; - union { struct srw_lock s; LONG l; } old, new; - BOOLEAN ret; + RTL_SRWLOCK old; + TRACE("%p\n", lock); + return srwlock_try_acquire_exclusive(lock, &old); +} + +/*********************************************************************** + * RtlAcquireSRWLockExclusive (NTDLL.@) + * + * NOTES + * Unlike RtlAcquireResourceExclusive this function doesn't allow + * nested calls from the same thread. "Upgrading" a shared access lock + * to an exclusive access lock also doesn't seem to be supported. + */ +void WINAPI RtlAcquireSRWLockExclusive( RTL_SRWLOCK *lock ) +{ + RTL_SRWLOCK old; + + TRACE("%p\n", lock); + + while (!srwlock_try_acquire_exclusive(lock, &old)) + if (srwlock_wait(lock, SRWLOCK_WAITER_STATE_IS_EXCLUSIVE, old)) + break; +} + +static BOOLEAN srwlock_try_acquire_shared(RTL_SRWLOCK *lock, RTL_SRWLOCK *old) +{ + RTL_SRWLOCK new; + USHORT tag; + ULONG_PTR shared_count; + struct srwlock_waiter *last;
do { - old.s = *u.s; - new.s = old.s; + old->Ptr = ReadPointerAcquire(&lock->Ptr); + TRACE("old = %p\n", old->Ptr); + tag = srwlock_get_tag(*old); + last = srwlock_get_waiter(*old); + shared_count = srwlock_get_shared_count(*old);
- if (!old.s.owners) - { - /* Not locked exclusive or shared. We can try to grab it. */ - new.s.owners = -1; - ret = TRUE; - } + if (tag & SRWLOCK_TAG_HAS_MULTIPLE_OWNERS) + return FALSE; + + if ((tag & SRWLOCK_TAG_LOCKED) && (shared_count == 0 || (tag & SRWLOCK_TAG_HAS_WAITERS))) + return FALSE; + + /* The lock is either locked shared, or not locked at all. We can try to grab it. */ + if (tag & SRWLOCK_TAG_HAS_WAITERS) + new = srwlock_from_waiter(last, tag | SRWLOCK_TAG_LOCKED); else - { - ret = FALSE; - } - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l); + new = srwlock_from_shared_owner_count(shared_count + 1, + tag | SRWLOCK_TAG_LOCKED); + } while (InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, + old->Ptr ) != old->Ptr);
- return ret; + return TRUE; }
/*********************************************************************** @@ -671,29 +854,183 @@ BOOLEAN WINAPI RtlTryAcquireSRWLockExclusive( RTL_SRWLOCK *lock ) */ BOOLEAN WINAPI RtlTryAcquireSRWLockShared( RTL_SRWLOCK *lock ) { - union { RTL_SRWLOCK *rtl; struct srw_lock *s; LONG *l; } u = { lock }; - union { struct srw_lock s; LONG l; } old, new; - BOOLEAN ret; + RTL_SRWLOCK old; + TRACE("%p\n", lock); + return srwlock_try_acquire_shared(lock, &old); +} + +/*********************************************************************** + * RtlAcquireSRWLockShared (NTDLL.@) + * + * NOTES + * Do not call this function recursively - it will only succeed when + * there are no threads waiting for an exclusive lock! + */ +void WINAPI RtlAcquireSRWLockShared( RTL_SRWLOCK *lock ) +{ + RTL_SRWLOCK old; + + TRACE("%p\n", lock); + + while (!srwlock_try_acquire_shared(lock, &old)) + if (srwlock_wait(lock, 0, old)) + break; +} + +/* Try to acquire the list lock and start waking waiters up. + * + * This function bails in the following cases: + * + * - the lock become locked, we should not try to wake anyone up. And the + * new owner of the lock will be doing the waking when it releases the + * lock. + * - someone else acquired the list lock. In this case they will be responsible + * of waking up the waiters. + * - no waiters remain. No one to wake up. + */ +static void srwlock_maybe_wake(RTL_SRWLOCK *lock, RTL_SRWLOCK old) +{ + RTL_SRWLOCK new, read; + UINT tag = srwlock_get_tag(old); + TRACE("\n"); + + /* Try to acquire the lock on the list. If we are not able to, meaning + * there is another thread (can be either an acquirer or a releaser) + * currently holding the list lock, we give up and leave the duty of + * waking waiters up to that thread. */ + while (tag == SRWLOCK_TAG_HAS_WAITERS) + { + struct srwlock_waiter *waiter = srwlock_get_waiter(old); + new = srwlock_from_waiter(waiter, tag | SRWLOCK_TAG_LIST_LOCKED); + read.Ptr = InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, old.Ptr); + if (read.Ptr == old.Ptr) { + /* If we do succeed in locking the list, we are responsible for + * waking up the waiters. */ + srwlock_wake(lock, waiter); + break; + } + old = read; + tag = srwlock_get_tag(old); + } +} +/*********************************************************************** + * RtlReleaseSRWLockExclusive (NTDLL.@) + */ +void WINAPI RtlReleaseSRWLockExclusive( RTL_SRWLOCK *lock ) +{ + RTL_SRWLOCK old; + + TRACE("%p\n", lock); + + /* Looks weird but this is how Windows does it. */ + old.Ptr = InterlockedAddPointer(&lock->Ptr, -1); + TRACE("after = %p\n", old.Ptr); + + srwlock_maybe_wake(lock, old); +} + +/*********************************************************************** + * RtlReleaseSRWLockShared (NTDLL.@) + */ +void WINAPI RtlReleaseSRWLockShared( RTL_SRWLOCK *lock ) +{ + RTL_SRWLOCK old, new; + USHORT tag; + LONG shared_count; + struct srwlock_waiter *last, *head; + + TRACE("%p\n", lock);
do { - old.s = *u.s; - new.s = old.s; + old.Ptr = ReadPointerAcquire(&lock->Ptr); + TRACE("old = %p\n", old.Ptr); + + tag = srwlock_get_tag(old); + last = srwlock_get_waiter(old);
- if (old.s.owners != -1 && !old.s.exclusive_waiters) + if (!(tag & SRWLOCK_TAG_LOCKED)) { - /* Not locked exclusive, and no exclusive waiters. - * We can try to grab it. */ - ++new.s.owners; - ret = TRUE; + /* interestingly this check is only done for shared locks. */ + EXCEPTION_RECORD record; + record.ExceptionAddress = RtlReleaseSRWLockShared; + record.ExceptionCode = STATUS_RESOURCE_NOT_OWNED; + record.ExceptionFlags = 0; + record.ExceptionRecord = NULL; + record.NumberParameters = 0; + return RtlRaiseException(&record); } - else + + if (tag & SRWLOCK_TAG_HAS_WAITERS) { - ret = FALSE; + /* We are only safe to access the list head if there are multiple owners, + * in which case only after the last owner has decremented `num_owners` + * can the list starts to be modified. OTOH when the HAS_MULTIPLE_OWNERS + * bit is not set, we know we are the sole owner without needing to + * consult the list. */ + if (tag & SRWLOCK_TAG_HAS_MULTIPLE_OWNERS) + { + /* last->head can be NULL if another thread is in the process + * of adding a waiter. If we reach this point we know the list + * head cannot change, and nodes won't be removed from the list. + * So we can safely scan backwards to find a valid head pointer.*/ + while (TRUE) { + head = ReadPointerNoFence((void **)&last->head); + if (head) + break; + last = last->prev; + } + shared_count = InterlockedDecrement((LONG *)&head->num_owners); + TRACE("shared_count in head = %ld\n", shared_count); + + /* Now, threads that got shared_count = either 1 or 0 have + * something to do here. The thread that got 1 needs to unset + * MULTIPLE_OWNERS, the other thread needs to unset LOCKED. + * + * We said earlier either of these bits being set blocks lock + * acquisition. Because otherwise would require strong ordering + * of these two unsets. If LOCKED is unset first, other threads + * would start acquiring/releasing the lock. Later when + * MULTIPLE_OWNERS is unset, it would scribble over lock state + * that has since changed, potentially making it invalid. + */ + if (shared_count > 1) + return; + + /* At most 2 threads can reach here. */ + if (shared_count == 1) + old.Ptr = InterlockedAndPointer(&lock->Ptr, ~(ULONG_PTR)SRWLOCK_TAG_HAS_MULTIPLE_OWNERS); + else + old.Ptr = InterlockedAndPointer(&lock->Ptr, ~(ULONG_PTR)SRWLOCK_TAG_LOCKED); + + TRACE("before = %p, shared_count = %ld\n", old.Ptr, shared_count); + tag = srwlock_get_tag(old); + if ((tag & SRWLOCK_TAG_LOCKED) && (tag & SRWLOCK_TAG_HAS_MULTIPLE_OWNERS)) + return; + + /* The thread that finished second will be the only one that reaches here. */ + } + else { + /* This thread is the sole owner of the lock. */ + old.Ptr = InterlockedAndPointer(&lock->Ptr, ~(ULONG_PTR)SRWLOCK_TAG_LOCKED); + TRACE("before = %p\n", old.Ptr); + } + + /* Only the last owner reaches here. */ + old.Ptr = (PVOID)((ULONG_PTR)old.Ptr & ~(ULONG_PTR)(SRWLOCK_TAG_HAS_MULTIPLE_OWNERS | SRWLOCK_TAG_LOCKED)); + return srwlock_maybe_wake(lock, old); } - } while (InterlockedCompareExchange( u.l, new.l, old.l ) != old.l);
- return ret; + shared_count = srwlock_get_shared_count(old) - 1; + if (shared_count == 0) + tag &= ~SRWLOCK_TAG_LOCKED; + if (shared_count == 1) + tag &= ~SRWLOCK_TAG_HAS_MULTIPLE_OWNERS; + + new = srwlock_from_shared_owner_count(shared_count, tag); + TRACE("new = %p\n", new.Ptr); + } while (InterlockedCompareExchangePointer(&lock->Ptr, new.Ptr, old.Ptr) != + old.Ptr); }
/***********************************************************************