fixes #1409 reader/writer lock desired

This provides the initial implementation, and converts the
transport lookup routines to use it.  This is probably of limited
performance benefit, but rwlock's may be useful in further future work.

2 files changed, 60 insertions, 19 deletions

diff --git a/src/platform/windows/win_impl.h b/src/platform/windows/win_impl.h
index 17260676..de4f8e5b 100644
--- a/src/platform/windows/win_impl.h
+++ b/src/platform/windows/win_impl.h
@@ -41,6 +41,11 @@ struct nni_plat_mtx {
 	int     init;
 };
 
+struct nni_rwlock {
+	SRWLOCK rwl;
+	BOOLEAN exclusive;
+};
+
 struct nni_plat_cv {
 	CONDITION_VARIABLE cv;
 	PSRWLOCK           srl;
diff --git a/src/platform/windows/win_thread.c b/src/platform/windows/win_thread.c
index 7cc87eb3..c069d3c9 100644
--- a/src/platform/windows/win_thread.c
+++ b/src/platform/windows/win_thread.c
@@ -77,6 +77,42 @@ nni_plat_mtx_unlock(nni_plat_mtx *mtx)
 }
 
 void
+nni_rwlock_init(nni_rwlock *rwl)
+{
+	InitializeSRWLock(&rwl->rwl);
+}
+
+void
+nni_rwlock_fini(nni_rwlock *rwl)
+{
+	rwl->exclusive = FALSE;
+}
+
+void
+nni_rwlock_rdlock(nni_rwlock *rwl)
+{
+	AcquireSRWLockShared(&rwl->rwl);
+}
+
+void
+nni_rwlock_wrlock(nni_rwlock *rwl)
+{
+	AcquireSRWLockExclusive(&rwl->rwl);
+	rwl->exclusive = TRUE;
+}
+
+void
+nni_rwlock_unlock(nni_rwlock *rwl)
+{
+	if (rwl->exclusive) {
+		rwl->exclusive = FALSE;
+		ReleaseSRWLockExclusive(&rwl->rwl);
+	} else {
+		ReleaseSRWLockShared(&rwl->rwl);
+	}
+}
+
+void
 nni_plat_cv_init(nni_plat_cv *cv, nni_plat_mtx *mtx)
 {
 	InitializeConditionVariable(&cv->cv);
@@ -112,7 +148,7 @@ nni_plat_cv_until(nni_plat_cv *cv, nni_time until)
 	if (now > until) {
 		msec = 0;
 	} else {
-		msec = (DWORD)(until - now);
+		msec = (DWORD) (until - now);
 	}
 
 	ok = SleepConditionVariableSRW(&cv->cv, cv->srl, msec, 0);
@@ -178,7 +214,7 @@ uint64_t
 nni_atomic_get64(nni_atomic_u64 *v)
 {
 
-	return ((uint64_t)(InterlockedExchangeAdd64(&v->v, 0)));
+	return ((uint64_t) (InterlockedExchangeAdd64(&v->v, 0)));
 }
 
 void
@@ -190,7 +226,7 @@ nni_atomic_set64(nni_atomic_u64 *v, uint64_t u)
 uint64_t
 nni_atomic_swap64(nni_atomic_u64 *v, uint64_t u)
 {
-	return ((uint64_t)(InterlockedExchange64(&v->v, (LONGLONG) u)));
+	return ((uint64_t) (InterlockedExchange64(&v->v, (LONGLONG) u)));
 }
 
 void
@@ -213,9 +249,9 @@ uint64_t
 nni_atomic_dec64_nv(nni_atomic_u64 *v)
 {
 #ifdef _WIN64
-	return ((uint64_t)(InterlockedDecrementRelease64(&v->v)));
+	return ((uint64_t) (InterlockedDecrementRelease64(&v->v)));
 #else
-	return ((uint64_t)(InterlockedDecrement64(&v->v)));
+	return ((uint64_t) (InterlockedDecrement64(&v->v)));
 #endif
 }
 
@@ -331,9 +367,9 @@ void
 nni_plat_thr_set_name(nni_plat_thr *thr, const char *name)
 {
 	if (set_thread_desc != NULL) {
-                wchar_t *wcs;
-                size_t len;
-		HANDLE h;
+		wchar_t *wcs;
+		size_t   len;
+		HANDLE   h;
 
 		if (thr == NULL) {
 			h = GetCurrentThread();
@@ -341,7 +377,7 @@ nni_plat_thr_set_name(nni_plat_thr *thr, const char *name)
 			h = thr->handle;
 		}
 
-                len = strlen(name) + 1;
+		len = strlen(name) + 1;
 		if ((wcs = nni_alloc(len * 2)) == NULL) {
 			return;
 		}
@@ -372,18 +408,18 @@ nni_plat_init(int (*helper)(void))
 		return (0); // fast path
 	}
 
-
-        AcquireSRWLockExclusive(&lock);
+	AcquireSRWLockExclusive(&lock);
 
 	if (!plat_inited) {
-                // Let's look up the function to set thread descriptions.
-                hKernel32 = LoadLibrary(TEXT("kernel32.dll"));
-                if (hKernel32 != NULL) {
-                        set_thread_desc = (pfnSetThreadDescription)
-                            GetProcAddress(hKernel32, "SetThreadDescription");
-                }
-
-                if (((rv = nni_win_io_sysinit()) != 0) ||
+		// Let's look up the function to set thread descriptions.
+		hKernel32 = LoadLibrary(TEXT("kernel32.dll"));
+		if (hKernel32 != NULL) {
+			set_thread_desc =
+			    (pfnSetThreadDescription) GetProcAddress(
+			        hKernel32, "SetThreadDescription");
+		}
+
+		if (((rv = nni_win_io_sysinit()) != 0) ||
 		    ((rv = nni_win_ipc_sysinit()) != 0) ||
 		    ((rv = nni_win_tcp_sysinit()) != 0) ||
 		    ((rv = nni_win_udp_sysinit()) != 0) ||