ntdll: Implement RtlTryAcquireSRWLockShared/Exclusive commands.

dlls/ntdll/ntdll.spec

@@ -891,6 +891,8 @@
 # @ stub RtlTraceDatabaseLock
 # @ stub RtlTraceDatabaseUnlock
 # @ stub RtlTraceDatabaseValidate
+@ stdcall RtlTryAcquireSRWLockExclusive(ptr)
+@ stdcall RtlTryAcquireSRWLockShared(ptr)
 @ stdcall RtlTryEnterCriticalSection(ptr)
 @ cdecl -i386 -norelay RtlUlongByteSwap() NTDLL_RtlUlongByteSwap
 @ cdecl -ret64 RtlUlonglongByteSwap(int64)

dlls/ntdll/sync.c

@@ -1535,6 +1535,10 @@ void WINAPI RtlAcquireSRWLockExclusive( RTL_SRWLOCK *lock )
 
 /***********************************************************************
  *              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 )
 {
@@ -1583,6 +1587,35 @@ void WINAPI RtlReleaseSRWLockShared( RTL_SRWLOCK *lock )
 }
 
 /***********************************************************************
+ *              RtlTryAcquireSRWLockExclusive (NTDLL.@)
+ *
+ * NOTES
+ *  Similar to AcquireSRWLockExclusive recusive calls are not allowed
+ *  and will fail with return value FALSE.
+ */
+BOOLEAN WINAPI RtlTryAcquireSRWLockExclusive( RTL_SRWLOCK *lock )
+{
+    return interlocked_cmpxchg( (int *)&lock->Ptr, SRWLOCK_MASK_IN_EXCLUSIVE |
+                                SRWLOCK_RES_EXCLUSIVE, 0 ) == 0;
+}
+
+/***********************************************************************
+ *              RtlTryAcquireSRWLockShared (NTDLL.@)
+ */
+BOOLEAN WINAPI RtlTryAcquireSRWLockShared( RTL_SRWLOCK *lock )
+{
+    unsigned int val, tmp;
+    for (val = *(unsigned int *)&lock->Ptr;; val = tmp)
+    {
+        if (val & SRWLOCK_MASK_EXCLUSIVE_QUEUE)
+            return FALSE;
+        if ((tmp = interlocked_cmpxchg( (int *)&lock->Ptr, val + SRWLOCK_RES_SHARED, val )) == val)
+            break;
+    }
+    return TRUE;
+}
+
+/***********************************************************************
  *           RtlInitializeConditionVariable   (NTDLL.@)
  *
  * Initializes the condition variable with NULL.

include/winternl.h

@@ -2512,6 +2512,8 @@ NTSYSAPI BOOLEAN   WINAPI RtlTimeFieldsToTime(PTIME_FIELDS,PLARGE_INTEGER);
 NTSYSAPI void      WINAPI RtlTimeToElapsedTimeFields(const LARGE_INTEGER *,PTIME_FIELDS);
 NTSYSAPI BOOLEAN   WINAPI RtlTimeToSecondsSince1970(const LARGE_INTEGER *,LPDWORD);
 NTSYSAPI BOOLEAN   WINAPI RtlTimeToSecondsSince1980(const LARGE_INTEGER *,LPDWORD);
+NTSYSAPI BOOLEAN   WINAPI RtlTryAcquireSRWLockExclusive(RTL_SRWLOCK *);
+NTSYSAPI BOOLEAN   WINAPI RtlTryAcquireSRWLockShared(RTL_SRWLOCK *);
 NTSYSAPI BOOL      WINAPI RtlTryEnterCriticalSection(RTL_CRITICAL_SECTION *);
 NTSYSAPI ULONGLONG __cdecl RtlUlonglongByteSwap(ULONGLONG);
 NTSYSAPI DWORD     WINAPI RtlUnicodeStringToAnsiSize(const UNICODE_STRING*);