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ntdll: Implement SRWLock functions using keyed events.

This commit is contained in:
Sebastian Lackner 2014-01-11 02:18:10 +01:00 committed by Alexandre Julliard
parent 663444ccb7
commit 31a283d4da
2 changed files with 154 additions and 10 deletions
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6
dlls/kernel32/tests/sync.c
View File

@ -1890,9 +1890,6 @@ static void test_srwlock_base(void)
WaitForSingleObject(h2, 100);
WaitForSingleObject(h3, 100);
/* the current implementation just consists of stubs and all tests fail */
todo_wine
{
ok(!srwlock_base_errors.wrong_execution_order,
"thread commands were executed in the wrong order (occurred %d times).\n",
srwlock_base_errors.wrong_execution_order);
@ -1916,7 +1913,6 @@ static void test_srwlock_base(void)
ok(!srwlock_base_errors.excl_not_preferred,
"thread waiting for exclusive access to the SHMLock was not preferred (occurred %d times).\n",
srwlock_base_errors.excl_not_preferred);
}
}
static SRWLOCK srwlock_example;
@ -1994,8 +1990,6 @@ static void test_srwlock_example(void)
WaitForSingleObject(h3, 1000);
ok(!srwlock_inside, "threads didn't terminate properly, srwlock_inside is %d.\n", srwlock_inside);
todo_wine
ok(!srwlock_example_errors, "errors occured while running SRWLock example test (number of errors: %d)\n",
srwlock_example_errors);

158
dlls/ntdll/sync.c
View File

@ -1382,8 +1382,127 @@ DWORD WINAPI RtlRunOnceExecuteOnce( RTL_RUN_ONCE *once, PRTL_RUN_ONCE_INIT_FN fu
return RtlRunOnceComplete( once, 0, context ? *context : NULL );
}
/* SRW locks implementation
*
* The memory layout used by the lock is:
*
* 32 31 16 0
* ________________ ________________
* | X| #exclusive | #shared |
* ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
* Since there is no space left for a separate counter of shared access
* threads inside the locked section the #shared field is used for multiple
* purposes. The following table lists all possible states the lock can be
* in, notation: [X, #exclusive, #shared]:
*
* [0, 0, N] -> locked by N shared access threads, if N=0 its unlocked
* [0, >=1, >=1] -> threads are requesting exclusive locks, but there are
* still shared access threads inside. #shared should not be incremented
* anymore!
* [1, >=1, >=0] -> lock is owned by an exclusive thread and the #shared
* counter can be used again to count the number of threads waiting in the
* queue for shared access.
*
* the following states are invalid and will never occur:
* [0, >=1, 0], [1, 0, >=0]
*
* The main problem arising from the fact that we have no separate counter
* of shared access threads inside the locked section is that in the state
* [0, >=1, >=1] above we cannot add additional waiting threads to the
* shared access queue - it wouldn't be possible to distinguish waiting
* threads and those that are still inside. To solve this problem the lock
* uses the following approach: A thread that isn't able to allocate a
* shared lock just uses the exclusive queue instead. As soon as the thread
* is woken up it is in the state [1, >=1, >=0]. In this state its again
* possible to use the shared access queue. The thread atomically moves
* itself to the shared access queue and releases the exclusive lock, such
* that the "real" exclusive access threads have a chance. As soon as they
* are all ready the shared access threads are processed.
*/
#define SRWLOCK_MASK_IN_EXCLUSIVE 0x80000000
#define SRWLOCK_MASK_EXCLUSIVE_QUEUE 0x7fff0000
#define SRWLOCK_MASK_SHARED_QUEUE 0x0000ffff
#define SRWLOCK_RES_EXCLUSIVE 0x00010000
#define SRWLOCK_RES_SHARED 0x00000001
#ifdef WORDS_BIGENDIAN
#define srwlock_key_exclusive(lock) (&lock->Ptr)
#define srwlock_key_shared(lock) ((void *)((char *)&lock->Ptr + 2))
#else
#define srwlock_key_exclusive(lock) ((void *)((char *)&lock->Ptr + 2))
#define srwlock_key_shared(lock) (&lock->Ptr)
#endif
static inline unsigned int srwlock_lock_exclusive( unsigned int *dest, int incr )
{
unsigned int val, tmp;
/* Atomically modifies the value of *dest by adding incr. If the shared
* queue is empty and there are threads waiting for exclusive access, then
* sets the mark SRWLOCK_MASK_IN_EXCLUSIVE to signal other threads that
* they are allowed to use again the shared queue counter. */
for (val = *dest;; val = tmp)
{
tmp = val + incr;
if ((tmp & SRWLOCK_MASK_EXCLUSIVE_QUEUE) && !(tmp & SRWLOCK_MASK_SHARED_QUEUE))
tmp |= SRWLOCK_MASK_IN_EXCLUSIVE;
if ((tmp = interlocked_cmpxchg( (int *)dest, tmp, val )) == val)
break;
}
return val;
}
static inline unsigned int srwlock_unlock_exclusive( unsigned int *dest, int incr )
{
unsigned int val, tmp;
/* Atomically modifies the value of *dest by adding incr. If the queue of
* threads waiting for exclusive access is empty, then remove the
* SRWLOCK_MASK_IN_EXCLUSIVE flag (only the shared queue counter will
* remain). */
for (val = *dest;; val = tmp)
{
tmp = val + incr;
if (!(tmp & SRWLOCK_MASK_EXCLUSIVE_QUEUE))
tmp &= SRWLOCK_MASK_SHARED_QUEUE;
if ((tmp = interlocked_cmpxchg( (int *)dest, tmp, val )) == val)
break;
}
return val;
}
static inline void srwlock_leave_exclusive( RTL_SRWLOCK *lock, unsigned int val )
{
/* Used when a thread leaves an exclusive section. If there are other
* exclusive access threads they are processed first, afterwards process
* the shared waiters. */
if (val & SRWLOCK_MASK_EXCLUSIVE_QUEUE)
NtReleaseKeyedEvent( keyed_event, srwlock_key_exclusive(lock), FALSE, NULL );
else
{
val &= SRWLOCK_MASK_SHARED_QUEUE; /* remove SRWLOCK_MASK_IN_EXCLUSIVE */
while (val--)
NtReleaseKeyedEvent( keyed_event, srwlock_key_shared(lock), FALSE, NULL );
}
}
static inline void srwlock_leave_shared( RTL_SRWLOCK *lock, unsigned int val )
{
/* Wake up one exclusive thread as soon as the last shared access thread
* has left. */
if ((val & SRWLOCK_MASK_EXCLUSIVE_QUEUE) && !(val & SRWLOCK_MASK_SHARED_QUEUE))
NtReleaseKeyedEvent( keyed_event, srwlock_key_exclusive(lock), FALSE, NULL );
}
/***********************************************************************
* RtlInitializeSRWLock (NTDLL.@)
*
* 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.
*/
void WINAPI RtlInitializeSRWLock( RTL_SRWLOCK *lock )
{
@ -1392,10 +1511,16 @@ void WINAPI RtlInitializeSRWLock( RTL_SRWLOCK *lock )
/***********************************************************************
* 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 )
{
FIXME( "%p stub\n", lock );
if (srwlock_lock_exclusive( (unsigned int *)&lock->Ptr, SRWLOCK_RES_EXCLUSIVE ))
NtWaitForKeyedEvent( keyed_event, srwlock_key_exclusive(lock), FALSE, NULL );
}
/***********************************************************************
@ -1403,7 +1528,30 @@ void WINAPI RtlAcquireSRWLockExclusive( RTL_SRWLOCK *lock )
*/
void WINAPI RtlAcquireSRWLockShared( RTL_SRWLOCK *lock )
{
FIXME( "%p stub\n", lock );
unsigned int val, tmp;
/* Acquires a shared lock. If it's currently not possible to add elements to
* the shared queue, then request exclusive access instead. */
for (val = *(unsigned int *)&lock->Ptr;; val = tmp)
{
if ((val & SRWLOCK_MASK_EXCLUSIVE_QUEUE) && !(val & SRWLOCK_MASK_IN_EXCLUSIVE))
tmp = val + SRWLOCK_RES_EXCLUSIVE;
else
tmp = val + SRWLOCK_RES_SHARED;
if ((tmp = interlocked_cmpxchg( (int *)&lock->Ptr, tmp, val )) == val)
break;
}
/* Drop exclusive access again and instead requeue for shared access. */
if ((val & SRWLOCK_MASK_EXCLUSIVE_QUEUE) && !(val & SRWLOCK_MASK_IN_EXCLUSIVE))
{
NtWaitForKeyedEvent( keyed_event, srwlock_key_exclusive(lock), FALSE, NULL );
val = srwlock_unlock_exclusive( (unsigned int *)&lock->Ptr, (SRWLOCK_RES_SHARED
- SRWLOCK_RES_EXCLUSIVE) ) - SRWLOCK_RES_EXCLUSIVE;
srwlock_leave_exclusive( lock, val );
}
if (val & SRWLOCK_MASK_EXCLUSIVE_QUEUE)
NtWaitForKeyedEvent( keyed_event, srwlock_key_shared(lock), FALSE, NULL );
}
/***********************************************************************
@ -1411,7 +1559,8 @@ void WINAPI RtlAcquireSRWLockShared( RTL_SRWLOCK *lock )
*/
void WINAPI RtlReleaseSRWLockExclusive( RTL_SRWLOCK *lock )
{
FIXME( "%p stub\n", lock );
srwlock_leave_exclusive( lock, srwlock_unlock_exclusive( (unsigned int *)&lock->Ptr,
- SRWLOCK_RES_EXCLUSIVE ) - SRWLOCK_RES_EXCLUSIVE );
}
/***********************************************************************
@ -1419,7 +1568,8 @@ void WINAPI RtlReleaseSRWLockExclusive( RTL_SRWLOCK *lock )
*/
void WINAPI RtlReleaseSRWLockShared( RTL_SRWLOCK *lock )
{
FIXME( "%p stub\n", lock );
srwlock_leave_shared( lock, srwlock_lock_exclusive( (unsigned int *)&lock->Ptr,
- SRWLOCK_RES_SHARED ) - SRWLOCK_RES_SHARED );
}
/***********************************************************************