lock: adopt the POSIX behaviour on Windows

Ideally we would do the lazy semaphore approach that Mach does.
Unfortunately, the queue wasn't getting drained as in that case.  A
follow up should investigate and fix the lazy allocation.

Author: compnerd

src/shims/lock.c

@@ -270,8 +270,7 @@ _pop_timer_resolution(DWORD ms)
 	if (ms) timeEndPeriod(ms);
 }
 
-void
-_dispatch_sema4_create_slow(_dispatch_sema4_t *s4, int policy DISPATCH_UNUSED)
+void _dispatch_sema4_init(_dispatch_sema4_t *sema, int policy)
 {
 	HANDLE tmp;
 
@@ -281,7 +280,7 @@ _dispatch_sema4_create_slow(_dispatch_sema4_t *s4, int policy DISPATCH_UNUSED)
 		_dispatch_temporary_resource_shortage();
 	}
 
-	if (!os_atomic_cmpxchg(s4, 0, tmp, relaxed)) {
+	if (!os_atomic_cmpxchg(sema, 0, tmp, relaxed)) {
 		CloseHandle(tmp);
 	}
 }

src/shims/lock.h

@@ -205,9 +205,9 @@ typedef HANDLE _dispatch_sema4_t;
 #define _DSEMA4_POLICY_LIFO 0
 #define _DSEMA4_TIMEOUT() ((errno) = ETIMEDOUT, -1)
 
-#define _dispatch_sema4_init(sema, policy) (void)(*(sema) = 0)
-#define _dispatch_sema4_is_created(sema)   (*(sema) != 0)
-void _dispatch_sema4_create_slow(_dispatch_sema4_t *sema, int policy);
+void _dispatch_sema4_init(_dispatch_sema4_t *sema, int policy);
+#define _dispatch_sema4_is_created(sema)   ((void)sema, 1)
+#define _dispatch_sema4_create_slow(sema, policy) ((void)sema, (void)policy)
 
 #else
 #error "port has to implement _dispatch_sema4_t"
@@ -285,9 +285,6 @@ _dispatch_thread_event_init(dispatch_thread_event_t dte)
 	dte->dte_value = 0;
 #else
 	_dispatch_sema4_init(&dte->dte_sema, _DSEMA4_POLICY_FIFO);
-#if defined(_WIN32)
-	_dispatch_sema4_create(&dte->dte_sema, _DSEMA4_POLICY_FIFO);
-#endif
 #endif
 }