fix

lib/isc/rwlock.c

@@ -26,6 +26,30 @@
 #include <isc/rwlock.h>
 #include <isc/util.h>
 
+#if defined(_MSC_VER)
+#include <intrin.h>
+#define isc_rwlock_pause() YieldProcessor()
+#elif defined(__x86_64__)
+#include <immintrin.h>
+#define isc_rwlock_pause() _mm_pause()
+#elif defined(__i386__)
+#define isc_rwlock_pause() __asm__ __volatile__("rep; nop")
+#elif defined(__ia64__)
+#define isc_rwlock_pause() __asm__ __volatile__("hint @pause")
+#elif defined(__arm__) && HAVE_ARM_YIELD
+#define isc_rwlock_pause() __asm__ __volatile__("yield")
+#elif defined(sun) && (defined(__sparc) || defined(__sparc__))
+#define isc_rwlock_pause() smt_pause()
+#elif (defined(__sparc) || defined(__sparc__)) && HAVE_SPARC_PAUSE
+#define isc_rwlock_pause() __asm__ __volatile__("pause")
+#elif defined(__ppc__) || defined(_ARCH_PPC) || defined(_ARCH_PWR) || \
+	defined(_ARCH_PWR2) || defined(_POWER)
+#define isc_rwlock_pause() __asm__ volatile("or 27,27,27")
+#else /* if defined(_MSC_VER) */
+#define isc_rwlock_pause()
+#endif /* if defined(_MSC_VER) */
+
+
 #if USE_PTHREAD_RWLOCK
 
 #include <errno.h>
@@ -50,15 +74,14 @@ isc_rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
 	case isc_rwlocktype_write:
 		while (true) {
 			REQUIRE(pthread_rwlock_wrlock(&rwl->rwlock) == 0);
+                        if (!atomic_load_acquire(&rwl->downgrade)) {
+                              break;
+                        }
 			/* Unlock if in middle of downgrade operation */
-			if (atomic_load_acquire(&rwl->downgrade)) {
-				REQUIRE(pthread_rwlock_unlock(&rwl->rwlock) ==
-					0);
-				while (atomic_load_acquire(&rwl->downgrade)) {
-				}
-				continue;
+                        REQUIRE(pthread_rwlock_unlock(&rwl->rwlock) == 0);
+                        while (atomic_load_acquire(&rwl->downgrade)) {
+                                isc_rwlock_pause();
 			}
-			break;
 		}
 		break;
 	default:
@@ -142,28 +165,6 @@ isc_rwlock_destroy(isc_rwlock_t *rwl) {
 #define RWLOCK_MAX_ADAPTIVE_COUNT 100
 #endif /* ifndef RWLOCK_MAX_ADAPTIVE_COUNT */
 
-#if defined(_MSC_VER)
-#include <intrin.h>
-#define isc_rwlock_pause() YieldProcessor()
-#elif defined(__x86_64__)
-#include <immintrin.h>
-#define isc_rwlock_pause() _mm_pause()
-#elif defined(__i386__)
-#define isc_rwlock_pause() __asm__ __volatile__("rep; nop")
-#elif defined(__ia64__)
-#define isc_rwlock_pause() __asm__ __volatile__("hint @pause")
-#elif defined(__arm__) && HAVE_ARM_YIELD
-#define isc_rwlock_pause() __asm__ __volatile__("yield")
-#elif defined(sun) && (defined(__sparc) || defined(__sparc__))
-#define isc_rwlock_pause() smt_pause()
-#elif (defined(__sparc) || defined(__sparc__)) && HAVE_SPARC_PAUSE
-#define isc_rwlock_pause() __asm__ __volatile__("pause")
-#elif defined(__ppc__) || defined(_ARCH_PPC) || defined(_ARCH_PWR) || \
-	defined(_ARCH_PWR2) || defined(_POWER)
-#define isc_rwlock_pause() __asm__ volatile("or 27,27,27")
-#else /* if defined(_MSC_VER) */
-#define isc_rwlock_pause()
-#endif /* if defined(_MSC_VER) */
 
 static isc_result_t
 isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type);