rw_locks applied

include/sync0rw.h

@@ -328,7 +328,17 @@ rw_lock_get_x_lock_count(
 Accessor functions for rw lock. */
 UNIV_INLINE
 ulint
-rw_lock_get_waiters(
+rw_lock_get_s_waiters(
+/*==================*/
+	rw_lock_t*	lock);
+UNIV_INLINE
+ulint
+rw_lock_get_x_waiters(
+/*==================*/
+	rw_lock_t*	lock);
+UNIV_INLINE
+ulint
+rw_lock_get_wx_waiters(
 /*================*/
 	rw_lock_t*	lock);
 UNIV_INLINE
@@ -412,6 +422,11 @@ rw_lock_debug_print(
 	rw_lock_debug_t*	info);	/* in: debug struct */
 #endif /* UNIV_SYNC_DEBUG */
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+/* This value means NOT_LOCKED */
+#define RW_LOCK_BIAS		0x00100000
+#endif
+
 /* NOTE! The structure appears here only for the compiler to know its size.
 Do not use its fields directly! The structure used in the spin lock
 implementation of a read-write lock. Several threads may have a shared lock
@@ -421,9 +436,9 @@ blocked by readers, a writer may queue for the lock by setting the writer
 field. Then no new readers are allowed in. */
 
 struct rw_lock_struct {
-	os_event_t	event;	/* Used by sync0arr.c for thread queueing */
-
-#ifdef __WIN__
+			/* Used by sync0arr.c for thread queueing */
+	os_event_t	s_event;	/* Used for s_lock */
+	os_event_t	x_event;	/* Used for x_lock */
 	os_event_t	wait_ex_event;	/* This windows specific event is
 				used by the thread which has set the
 				lock state to RW_LOCK_WAIT_EX. The
@@ -431,30 +446,34 @@ struct rw_lock_struct {
 				thread will be the next one to proceed
 				once the current the event gets
 				signalled. See LEMMA 2 in sync0sync.c */
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	volatile lint	lock_word;	/* Used by using atomic builtin */
 #endif
 
-	ulint	reader_count;	/* Number of readers who have locked this
+	volatile ulint	reader_count;	/* Number of readers who have locked this
 				lock in the shared mode */
-	ulint	writer;		/* This field is set to RW_LOCK_EX if there
+	volatile ulint	writer;		/* This field is set to RW_LOCK_EX if there
 				is a writer owning the lock (in exclusive
 				mode), RW_LOCK_WAIT_EX if a writer is
 				queueing for the lock, and
 				RW_LOCK_NOT_LOCKED, otherwise. */
-	os_thread_id_t	writer_thread;
+	volatile os_thread_id_t	writer_thread;
 				/* Thread id of a possible writer thread */
-	ulint	writer_count;	/* Number of times the same thread has
+	volatile ulint	writer_count;	/* Number of times the same thread has
 				recursively locked the lock in the exclusive
 				mode */
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_t	mutex;		/* The mutex protecting rw_lock_struct */
+#endif
 	ulint	pass;		/* Default value 0. This is set to some
 				value != 0 given by the caller of an x-lock
 				operation, if the x-lock is to be passed to
 				another thread to unlock (which happens in
 				asynchronous i/o). */
-	ulint	waiters;	/* This ulint is set to 1 if there are
-				waiters (readers or writers) in the global
-				wait array, waiting for this rw_lock.
-				Otherwise, == 0. */
+	volatile ulint	s_waiters;	/* 1: there are waiters (s_lock) */
+	volatile ulint	x_waiters;	/* 1: there are waiters (x_lock) */
+	volatile ulint	wait_ex_waiters;	/* 1: there are waiters (wait_ex) */
 	UT_LIST_NODE_T(rw_lock_t) list;
 				/* All allocated rw locks are put into a
 				list */
@@ -467,7 +486,7 @@ struct rw_lock_struct {
 	const char*	cfile_name;/* File name where lock created */
 	const char*	last_s_file_name;/* File name where last s-locked */
 	const char*	last_x_file_name;/* File name where last x-locked */
-	ibool		writer_is_wait_ex;
+	volatile ibool		writer_is_wait_ex;
 				/* This is TRUE if the writer field is
 				RW_LOCK_WAIT_EX; this field is located far
 				from the memory update hotspot fields which

include/sync0rw.ic

@@ -47,20 +47,52 @@ rw_lock_remove_debug_info(
 Accessor functions for rw lock. */
 UNIV_INLINE
 ulint
-rw_lock_get_waiters(
+rw_lock_get_s_waiters(
 /*================*/
 	rw_lock_t*	lock)
 {
-	return(lock->waiters);
+	return(lock->s_waiters);
+}
+UNIV_INLINE
+ulint
+rw_lock_get_x_waiters(
+/*================*/
+	rw_lock_t*	lock)
+{
+	return(lock->x_waiters);
+}
+UNIV_INLINE
+ulint
+rw_lock_get_wx_waiters(
+/*================*/
+	rw_lock_t*      lock)
+{
+	return(lock->wait_ex_waiters);
+}
+UNIV_INLINE
+void
+rw_lock_set_s_waiters(
+	rw_lock_t*	lock,
+	ulint		flag)
+{
+	lock->s_waiters = flag;
 }
 UNIV_INLINE
 void
-rw_lock_set_waiters(
+rw_lock_set_x_waiters(
+	rw_lock_t*	lock,
+	ulint		flag)
+{
+	lock->x_waiters = flag;
+}
+UNIV_INLINE
+void
+rw_lock_set_wx_waiters(
 /*================*/
 	rw_lock_t*      lock,
 	ulint           flag)
 {
-	lock->waiters = flag;
+	lock->wait_ex_waiters = flag;
 }
 UNIV_INLINE
 ulint
@@ -68,7 +100,19 @@ rw_lock_get_writer(
 /*===============*/
 	rw_lock_t*	lock)
 {
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (lock->writer == RW_LOCK_NOT_LOCKED) {
+		return(RW_LOCK_NOT_LOCKED);
+	}
+
+	if (lock->writer_is_wait_ex) {
+		return(RW_LOCK_WAIT_EX);
+	} else {
+		return(RW_LOCK_EX);
+	}
+#else
 	return(lock->writer);
+#endif
 }
 UNIV_INLINE
 void
@@ -96,6 +140,7 @@ rw_lock_set_reader_count(
 {
 	lock->reader_count = count;
 }
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 UNIV_INLINE
 mutex_t*
 rw_lock_get_mutex(
@@ -104,6 +149,7 @@ rw_lock_get_mutex(
 {
 	return(&(lock->mutex));
 }
+#endif
 
 /**********************************************************************
 Returns the value of writer_count for the lock. Does not reserve the lock
@@ -133,13 +179,27 @@ rw_lock_s_lock_low(
 	const char*	file_name, /* in: file name where lock requested */
 	ulint		line)	/* in: line where requested */
 {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	ut_ad(mutex_own(rw_lock_get_mutex(lock)));
+#endif
 
 	/* Check if the writer field is free */
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (UNIV_LIKELY(rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED)) {
+		/* try s-lock */
+		if(__sync_sub_and_fetch(&(lock->lock_word),1) <= 0) {
+			/* fail */
+			__sync_fetch_and_add(&(lock->lock_word),1);
+			return(FALSE);  /* locking did not succeed */
+		}
+		/* success */
+		__sync_fetch_and_add(&(lock->reader_count),1);
+#else
 	if (UNIV_LIKELY(lock->writer == RW_LOCK_NOT_LOCKED)) {
 		/* Set the shared lock by incrementing the reader count */
 		lock->reader_count++;
+#endif
 
 #ifdef UNIV_SYNC_DEBUG
 		rw_lock_add_debug_info(lock, pass, RW_LOCK_SHARED, file_name,
@@ -166,11 +226,15 @@ rw_lock_s_lock_direct(
 	const char*	file_name,	/* in: file name where requested */
 	ulint		line)		/* in: line where lock requested */
 {
-	ut_ad(lock->writer == RW_LOCK_NOT_LOCKED);
+	ut_ad(rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED);
 	ut_ad(rw_lock_get_reader_count(lock) == 0);
 
 	/* Set the shared lock by incrementing the reader count */
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	__sync_fetch_and_add(&(lock->reader_count),1);
+#else
 	lock->reader_count++;
+#endif
 
 	lock->last_s_file_name = file_name;
 	lock->last_s_line = line;
@@ -198,7 +262,11 @@ rw_lock_x_lock_direct(
 
 	rw_lock_set_writer(lock, RW_LOCK_EX);
 	lock->writer_thread = os_thread_get_curr_id();
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	__sync_fetch_and_add(&(lock->writer_count),1);
+#else
 	lock->writer_count++;
+#endif
 	lock->pass = 0;
 
 	lock->last_x_file_name = file_name;
@@ -240,15 +308,21 @@ rw_lock_s_lock_func(
 	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED)); /* see NOTE above */
 #endif /* UNIV_SYNC_DEBUG */
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(rw_lock_get_mutex(lock));
+#endif
 
 	if (UNIV_LIKELY(rw_lock_s_lock_low(lock, pass, file_name, line))) {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 		return; /* Success */
 	} else {
 		/* Did not succeed, try spin wait */
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 		rw_lock_s_lock_spin(lock, pass, file_name, line);
 
@@ -271,11 +345,23 @@ rw_lock_s_lock_func_nowait(
 {
 	ibool	success	= FALSE;
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
+		/* try s-lock */
+		if(__sync_sub_and_fetch(&(lock->lock_word),1) <= 0) {
+			/* fail */
+			__sync_fetch_and_add(&(lock->lock_word),1);
+			return(FALSE);	/* locking did not succeed */
+		}
+		/* success */
+		__sync_fetch_and_add(&(lock->reader_count),1);
+#else
 	mutex_enter(rw_lock_get_mutex(lock));
 
 	if (lock->writer == RW_LOCK_NOT_LOCKED) {
 		/* Set the shared lock by incrementing the reader count */
 		lock->reader_count++;
+#endif
 
 #ifdef UNIV_SYNC_DEBUG
 		rw_lock_add_debug_info(lock, 0, RW_LOCK_SHARED, file_name,
@@ -288,7 +374,9 @@ rw_lock_s_lock_func_nowait(
 		success = TRUE;
 	}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 	return(success);
 }
@@ -308,6 +396,55 @@ rw_lock_x_lock_func_nowait(
 {
 	ibool		success		= FALSE;
 	os_thread_id_t	curr_thread	= os_thread_get_curr_id();
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if ((lock->lock_word == RW_LOCK_BIAS)
+			&& rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
+		/* try x-lock */
+		if(__sync_sub_and_fetch(&(lock->lock_word),
+				RW_LOCK_BIAS) == 0) {
+			/* success */
+			/* try to lock writer */
+			if(__sync_lock_test_and_set(&(lock->writer),RW_LOCK_EX)
+					== RW_LOCK_NOT_LOCKED) {
+				/* success */
+				lock->writer_thread = curr_thread;
+				lock->pass = 0;
+				lock->writer_is_wait_ex = FALSE;
+				/* next function may work as memory barrier */
+			relock:
+				__sync_fetch_and_add(&(lock->writer_count),1);
+
+#ifdef UNIV_SYNC_DEBUG
+				rw_lock_add_debug_info(lock, 0, RW_LOCK_EX, file_name, line);
+#endif
+
+				lock->last_x_file_name = file_name;
+				lock->last_x_line = line;
+
+				ut_ad(rw_lock_validate(lock));
+
+				return(TRUE);
+			} else {
+				/* x-unlock */
+				__sync_fetch_and_add(&(lock->lock_word),
+					RW_LOCK_BIAS);
+			}
+		} else {
+			/* fail (x-lock) */
+			__sync_fetch_and_add(&(lock->lock_word),RW_LOCK_BIAS);
+		}
+	}
+
+	if (lock->pass == 0
+			&& os_thread_eq(lock->writer_thread, curr_thread)
+			&& rw_lock_get_writer(lock) == RW_LOCK_EX) {
+		goto relock;
+	}
+
+	ut_ad(rw_lock_validate(lock));
+
+	return(FALSE);
+#else
 	mutex_enter(rw_lock_get_mutex(lock));
 
 	if (UNIV_UNLIKELY(rw_lock_get_reader_count(lock) != 0)) {
@@ -338,6 +475,7 @@ relock:
 	ut_ad(rw_lock_validate(lock));
 
 	return(success);
+#endif
 }
 
 /**********************************************************************
@@ -353,16 +491,33 @@ rw_lock_s_unlock_func(
 #endif
 	)
 {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_t*	mutex	= &(lock->mutex);
-	ibool		sg	= FALSE;
+#endif
+	ibool		x_sg	= FALSE;
+	ibool		wx_sg	= FALSE;
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	ibool		last	= FALSE;
+#endif
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	/* Acquire the mutex protecting the rw-lock fields */
 	mutex_enter(mutex);
+#endif
 
 	/* Reset the shared lock by decrementing the reader count */
 
 	ut_a(lock->reader_count > 0);
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	/* unlock lock_word */
+	__sync_fetch_and_add(&(lock->lock_word),1);
+
+	if(__sync_sub_and_fetch(&(lock->reader_count),1) == 0) {
+		last = TRUE;
+	}
+#else
 	lock->reader_count--;
+#endif
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, pass, RW_LOCK_SHARED);
@@ -371,20 +526,36 @@ rw_lock_s_unlock_func(
 	/* If there may be waiters and this was the last s-lock,
 	signal the object */
 
-	if (UNIV_UNLIKELY(lock->waiters)
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (UNIV_UNLIKELY(last && lock->wait_ex_waiters)) {
+#else
+	if (UNIV_UNLIKELY(lock->wait_ex_waiters)
 	    && lock->reader_count == 0) {
-		sg = TRUE;
+#endif
+		wx_sg = TRUE;
 
-		rw_lock_set_waiters(lock, 0);
+		rw_lock_set_wx_waiters(lock, 0);
 	}
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	else if (UNIV_UNLIKELY(last && lock->x_waiters)) {
+#else
+	else if (UNIV_UNLIKELY(lock->x_waiters)
+		 && lock->reader_count == 0) {
+#endif
+		x_sg = TRUE;
 
+		rw_lock_set_x_waiters(lock, 0);
+	}
+
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(mutex);
+#endif
 
-	if (UNIV_UNLIKELY(sg)) {
-#ifdef __WIN__
+	if (UNIV_UNLIKELY(wx_sg)) {
 		os_event_set(lock->wait_ex_event);
-#endif
-		os_event_set(lock->event);
+		sync_array_object_signalled(sync_primary_wait_array);
+	} else if (UNIV_UNLIKELY(x_sg)) {
+		os_event_set(lock->x_event);
 		sync_array_object_signalled(sync_primary_wait_array);
 	}
 
@@ -408,13 +579,19 @@ rw_lock_s_unlock_direct(
 
 	ut_ad(lock->reader_count > 0);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	__sync_sub_and_fetch(&(lock->reader_count),1);
+#else
 	lock->reader_count--;
+#endif
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, 0, RW_LOCK_SHARED);
 #endif
 
-	ut_ad(!lock->waiters);
+	ut_ad(!lock->s_waiters);
+	ut_ad(!lock->x_waiters);
+	ut_ad(!lock->wait_ex_waiters);
 	ut_ad(rw_lock_validate(lock));
 #ifdef UNIV_SYNC_PERF_STAT
 	rw_s_exit_count++;
@@ -434,41 +611,81 @@ rw_lock_x_unlock_func(
 #endif
 	)
 {
-	ibool	sg	= FALSE;
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	ibool	last	= FALSE;
+#endif
+	ibool	s_sg	= FALSE;
+	ibool	x_sg	= FALSE;
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	/* Acquire the mutex protecting the rw-lock fields */
 	mutex_enter(&(lock->mutex));
+#endif
 
 	/* Reset the exclusive lock if this thread no longer has an x-mode
 	lock */
 
 	ut_ad(lock->writer_count > 0);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if(__sync_sub_and_fetch(&(lock->writer_count),1) == 0) {
+		last = TRUE;
+	}
+
+	if (last) {
+		/* unlock lock_word */
+		__sync_fetch_and_add(&(lock->lock_word),RW_LOCK_BIAS);
+
+		/* FIXME: It is a value of bad manners for pthread.
+			  But we shouldn't keep an ID of not-owner. */
+		lock->writer_thread = -1;
+
+		/* atomic operation may be safer about memory order. */
+		rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
+		__sync_synchronize();
+	}
+#else
 	lock->writer_count--;
 
 	if (lock->writer_count == 0) {
 		rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
 	}
+#endif
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, pass, RW_LOCK_EX);
 #endif
 
 	/* If there may be waiters, signal the lock */
-	if (UNIV_UNLIKELY(lock->waiters)
-	    && lock->writer_count == 0) {
-
-		sg = TRUE;
-		rw_lock_set_waiters(lock, 0);
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (last) {
+#else
+	if (lock->writer_count == 0) {
+#endif
+		if(lock->s_waiters){
+			s_sg = TRUE;
+			rw_lock_set_s_waiters(lock, 0);
+		}
+		if(lock->x_waiters){
+			x_sg = TRUE;
+			rw_lock_set_x_waiters(lock, 0);
+		}
 	}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(&(lock->mutex));
+#endif
 
-	if (UNIV_UNLIKELY(sg)) {
+	if (UNIV_UNLIKELY(s_sg)) {
+		os_event_set(lock->s_event);
+		sync_array_object_signalled(sync_primary_wait_array);
+	}
+	if (UNIV_UNLIKELY(x_sg)) {
 #ifdef __WIN__
+		/* I doubt the necessity of it. */
 		os_event_set(lock->wait_ex_event);
 #endif
-		os_event_set(lock->event);
+		os_event_set(lock->x_event);
 		sync_array_object_signalled(sync_primary_wait_array);
 	}
 
@@ -493,9 +710,13 @@ rw_lock_x_unlock_direct(
 
 	ut_ad(lock->writer_count > 0);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if(__sync_sub_and_fetch(&(lock->writer_count),1) == 0) {
+#else
 	lock->writer_count--;
 
 	if (lock->writer_count == 0) {
+#endif
 		rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
 	}
 
@@ -503,7 +724,9 @@ rw_lock_x_unlock_direct(
 	rw_lock_remove_debug_info(lock, 0, RW_LOCK_EX);
 #endif
 
-	ut_ad(!lock->waiters);
+	ut_ad(!lock->s_waiters);
+	ut_ad(!lock->x_waiters);
+	ut_ad(!lock->wait_ex_waiters);
 	ut_ad(rw_lock_validate(lock));
 
 #ifdef UNIV_SYNC_PERF_STAT

sync/sync0arr.c

@@ -307,13 +307,13 @@ sync_cell_event_reset(
 {
 	if (type == SYNC_MUTEX) {
 		return(os_event_reset(((mutex_t *) object)->event));
-#ifdef __WIN__
 	} else if (type == RW_LOCK_WAIT_EX) {
 		return(os_event_reset(
 		       ((rw_lock_t *) object)->wait_ex_event));
-#endif
-	} else {
-		return(os_event_reset(((rw_lock_t *) object)->event));
+	} else if (type == RW_LOCK_SHARED) {
+		return(os_event_reset(((rw_lock_t *) object)->s_event));
+	} else { /* RW_LOCK_EX */
+		return(os_event_reset(((rw_lock_t *) object)->x_event));
 	}
 }
 
@@ -413,15 +413,12 @@ sync_array_wait_event(
 
 	if (cell->request_type == SYNC_MUTEX) {
 		event = ((mutex_t*) cell->wait_object)->event;
-#ifdef __WIN__
-	/* On windows if the thread about to wait is the one which
-	has set the state of the rw_lock to RW_LOCK_WAIT_EX, then
-	it waits on a special event i.e.: wait_ex_event. */
 	} else if (cell->request_type == RW_LOCK_WAIT_EX) {
 		event = ((rw_lock_t*) cell->wait_object)->wait_ex_event;
-#endif
+	} else if (cell->request_type == RW_LOCK_SHARED) {
+		event = ((rw_lock_t*) cell->wait_object)->s_event;
 	} else {
-		event = ((rw_lock_t*) cell->wait_object)->event;
+		event = ((rw_lock_t*) cell->wait_object)->x_event;
 	}
 
 		cell->waiting = TRUE;
@@ -462,6 +459,7 @@ sync_array_cell_print(
 	mutex_t*	mutex;
 	rw_lock_t*	rwlock;
 	ulint		type;
+	ulint		writer;
 
 	type = cell->request_type;
 
@@ -491,12 +489,10 @@ sync_array_cell_print(
 			(ulong) mutex->waiters);
 
 	} else if (type == RW_LOCK_EX
-#ifdef __WIN__
 		   || type == RW_LOCK_WAIT_EX
-#endif
 		   || type == RW_LOCK_SHARED) {
 
-		fputs(type == RW_LOCK_EX ? "X-lock on" : "S-lock on", file);
+		fputs(type == RW_LOCK_SHARED ? "S-lock on" : "X-lock on", file);
 
 		rwlock = cell->old_wait_rw_lock;
 
@@ -504,22 +500,24 @@ sync_array_cell_print(
 			" RW-latch at %p created in file %s line %lu\n",
 			(void*) rwlock, rwlock->cfile_name,
 			(ulong) rwlock->cline);
-		if (rwlock->writer != RW_LOCK_NOT_LOCKED) {
+		writer = rw_lock_get_writer(rwlock);
+		if (writer != RW_LOCK_NOT_LOCKED) {
 			fprintf(file,
 				"a writer (thread id %lu) has"
 				" reserved it in mode %s",
 				(ulong) os_thread_pf(rwlock->writer_thread),
-				rwlock->writer == RW_LOCK_EX
+				writer == RW_LOCK_EX
 				? " exclusive\n"
 				: " wait exclusive\n");
 		}
 
 		fprintf(file,
-			"number of readers %lu, waiters flag %lu\n"
+			"number of readers %lu, s_waiters flag %lu, x_waiters flag %lu\n"
 			"Last time read locked in file %s line %lu\n"
 			"Last time write locked in file %s line %lu\n",
 			(ulong) rwlock->reader_count,
-			(ulong) rwlock->waiters,
+			(ulong) rwlock->s_waiters,
+			(ulong) (rwlock->x_waiters || rwlock->wait_ex_waiters),
 			rwlock->last_s_file_name,
 			(ulong) rwlock->last_s_line,
 			rwlock->last_x_file_name,
@@ -844,11 +842,15 @@ sync_array_object_signalled(
 /*========================*/
 	sync_array_t*	arr)	/* in: wait array */
 {
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	__sync_fetch_and_add(&(arr->sg_count),1);
+#else
 	sync_array_enter(arr);
 
 	arr->sg_count++;
 
 	sync_array_exit(arr);
+#endif
 }
 
 /**************************************************************************
@@ -889,19 +891,23 @@ sync_arr_wake_threads_if_sema_free(void)
 
 					mutex = cell->wait_object;
 					os_event_set(mutex->event);
-#ifdef __WIN__
 				} else if (cell->request_type
 					   == RW_LOCK_WAIT_EX) {
 					rw_lock_t*	lock;
 
 					lock = cell->wait_object;
 					os_event_set(lock->wait_ex_event);
-#endif
+				} else if (cell->request_type
+					   == RW_LOCK_SHARED) {
+					rw_lock_t*	lock;
+
+					lock = cell->wait_object;
+					os_event_set(lock->s_event);
 				} else {
 					rw_lock_t*      lock;
 
 					lock = cell->wait_object;
-					os_event_set(lock->event);
+					os_event_set(lock->x_event);
 				}
 			}
 		}

sync/sync0rw.c

@@ -119,6 +119,7 @@ rw_lock_create_func(
 	/* If this is the very first time a synchronization object is
 	created, then the following call initializes the sync system. */
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_create(rw_lock_get_mutex(lock), SYNC_NO_ORDER_CHECK);
 
 	lock->mutex.cfile_name = cfile_name;
@@ -128,8 +129,14 @@ rw_lock_create_func(
 	lock->mutex.cmutex_name = cmutex_name;
 	lock->mutex.mutex_type = 1;
 #endif /* UNIV_DEBUG && !UNIV_HOTBACKUP */
+#endif /* !HAVE_GCC_ATOMIC_BUILTINS */
 
-	rw_lock_set_waiters(lock, 0);
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	lock->lock_word = RW_LOCK_BIAS;
+#endif
+	rw_lock_set_s_waiters(lock, 0);
+	rw_lock_set_x_waiters(lock, 0);
+	rw_lock_set_wx_waiters(lock, 0);
 	rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
 	lock->writer_count = 0;
 	rw_lock_set_reader_count(lock, 0);
@@ -151,11 +158,9 @@ rw_lock_create_func(
 	lock->last_x_file_name = "not yet reserved";
 	lock->last_s_line = 0;
 	lock->last_x_line = 0;
-	lock->event = os_event_create(NULL);
-
-#ifdef __WIN__
+	lock->s_event = os_event_create(NULL);
+	lock->x_event = os_event_create(NULL);
 	lock->wait_ex_event = os_event_create(NULL);
-#endif
 
 	mutex_enter(&rw_lock_list_mutex);
 
@@ -181,19 +186,21 @@ rw_lock_free(
 {
 	ut_ad(rw_lock_validate(lock));
 	ut_a(rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED);
-	ut_a(rw_lock_get_waiters(lock) == 0);
+	ut_a(rw_lock_get_s_waiters(lock) == 0);
+	ut_a(rw_lock_get_x_waiters(lock) == 0);
+	ut_a(rw_lock_get_wx_waiters(lock) == 0);
 	ut_a(rw_lock_get_reader_count(lock) == 0);
 
 	lock->magic_n = 0;
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_free(rw_lock_get_mutex(lock));
+#endif
 
 	mutex_enter(&rw_lock_list_mutex);
-	os_event_free(lock->event);
-
-#ifdef __WIN__
+	os_event_free(lock->s_event);
+	os_event_free(lock->x_event);
 	os_event_free(lock->wait_ex_event);
-#endif
 
 	if (UT_LIST_GET_PREV(list, lock)) {
 		ut_a(UT_LIST_GET_PREV(list, lock)->magic_n == RW_LOCK_MAGIC_N);
@@ -211,6 +218,8 @@ rw_lock_free(
 /**********************************************************************
 Checks that the rw-lock has been initialized and that there are no
 simultaneous shared and exclusive locks. */
+/* MEMO: If HAVE_GCC_ATOMIC_BUILTINS, we should use this function statically. */
+ 
 UNIV_INTERN
 ibool
 rw_lock_validate(
@@ -219,7 +228,9 @@ rw_lock_validate(
 {
 	ut_a(lock);
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(rw_lock_get_mutex(lock));
+#endif
 
 	ut_a(lock->magic_n == RW_LOCK_MAGIC_N);
 	ut_a((rw_lock_get_reader_count(lock) == 0)
@@ -227,11 +238,17 @@ rw_lock_validate(
 	ut_a((rw_lock_get_writer(lock) == RW_LOCK_EX)
 	     || (rw_lock_get_writer(lock) == RW_LOCK_WAIT_EX)
 	     || (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED));
-	ut_a((rw_lock_get_waiters(lock) == 0)
-	     || (rw_lock_get_waiters(lock) == 1));
+	ut_a((rw_lock_get_s_waiters(lock) == 0)
+	     || (rw_lock_get_s_waiters(lock) == 1));
+	ut_a((rw_lock_get_x_waiters(lock) == 0)
+	     || (rw_lock_get_x_waiters(lock) == 1));
+	ut_a((rw_lock_get_wx_waiters(lock) == 0)
+	     || (rw_lock_get_wx_waiters(lock) == 1));
 	ut_a((lock->writer != RW_LOCK_EX) || (lock->writer_count > 0));
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 	return(TRUE);
 }
@@ -258,13 +275,14 @@ rw_lock_s_lock_spin(
 	ut_ad(rw_lock_validate(lock));
 
 lock_loop:
+	i = 0;
+spin_loop:
 	rw_s_spin_wait_count++;
 
 	/* Spin waiting for the writer field to become free */
-	i = 0;
 
-	while (rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED
-	       && i < SYNC_SPIN_ROUNDS) {
+	while (i < SYNC_SPIN_ROUNDS
+	       && rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED) {
 		if (srv_spin_wait_delay) {
 			ut_delay(ut_rnd_interval(0, srv_spin_wait_delay));
 		}
@@ -285,15 +303,27 @@ rw_lock_s_lock_spin(
 			lock->cfile_name, (ulong) lock->cline, (ulong) i);
 	}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(rw_lock_get_mutex(lock));
+#endif
 
 	/* We try once again to obtain the lock */
 
 	if (TRUE == rw_lock_s_lock_low(lock, pass, file_name, line)) {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 		return; /* Success */
 	} else {
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+		/* like sync0sync.c doing */
+		i++;
+
+		if (i < SYNC_SPIN_ROUNDS) {
+			goto spin_loop;
+		}
+#endif
 		/* If we get here, locking did not succeed, we may
 		suspend the thread to wait in the wait array */
 
@@ -304,9 +334,19 @@ rw_lock_s_lock_spin(
 					file_name, line,
 					&index);
 
-		rw_lock_set_waiters(lock, 1);
+		rw_lock_set_s_waiters(lock, 1);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+		/* like sync0sync.c doing */
+		for (i = 0; i < 4; i++) {
+			if (TRUE == rw_lock_s_lock_low(lock, pass, file_name, line)) {
+				sync_array_free_cell(sync_primary_wait_array, index);
+				return; /* Success */
+			}
+		}
+#else
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 		if (srv_print_latch_waits) {
 			fprintf(stderr,
@@ -343,13 +383,19 @@ rw_lock_x_lock_move_ownership(
 {
 	ut_ad(rw_lock_is_locked(lock, RW_LOCK_EX));
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(&(lock->mutex));
+#endif
 
 	lock->writer_thread = os_thread_get_curr_id();
 
 	lock->pass = 0;
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(&(lock->mutex));
+#else
+	__sync_synchronize();
+#endif
 }
 
 /**********************************************************************
@@ -367,6 +413,89 @@ rw_lock_x_lock_low(
 	const char*	file_name,/* in: file name where lock requested */
 	ulint		line)	/* in: line where requested */
 {
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	os_thread_id_t	curr_thread	= os_thread_get_curr_id();
+
+	/* try to lock writer */
+	if(__sync_lock_test_and_set(&(lock->writer),RW_LOCK_EX)
+			== RW_LOCK_NOT_LOCKED) {
+		/* success */
+		/* obtain RW_LOCK_WAIT_EX right */
+		lock->writer_thread = curr_thread;
+		lock->pass = pass;
+		lock->writer_is_wait_ex = TRUE;
+		/* atomic operation may be safer about memory order. */
+		__sync_synchronize();
+#ifdef UNIV_SYNC_DEBUG
+		rw_lock_add_debug_info(lock, pass, RW_LOCK_WAIT_EX,
+					file_name, line);
+#endif
+	}
+
+	if (!os_thread_eq(lock->writer_thread, curr_thread)) {
+		return(RW_LOCK_NOT_LOCKED);
+	}
+
+	switch(rw_lock_get_writer(lock)) {
+	    case RW_LOCK_WAIT_EX:
+		/* have right to try x-lock */
+		if (lock->lock_word == RW_LOCK_BIAS) {
+			/* try x-lock */
+			if(__sync_sub_and_fetch(&(lock->lock_word),
+					RW_LOCK_BIAS) == 0) {
+				/* success */
+				lock->pass = pass;
+				lock->writer_is_wait_ex = FALSE;
+				__sync_fetch_and_add(&(lock->writer_count),1);
+
+#ifdef UNIV_SYNC_DEBUG
+				rw_lock_remove_debug_info(lock, pass, RW_LOCK_WAIT_EX);
+				rw_lock_add_debug_info(lock, pass, RW_LOCK_EX,
+							file_name, line);
+#endif
+
+				lock->last_x_file_name = file_name;
+				lock->last_x_line = line;
+
+				/* Locking succeeded, we may return */
+				return(RW_LOCK_EX);
+			} else {
+				/* fail */
+				__sync_fetch_and_add(&(lock->lock_word),
+					RW_LOCK_BIAS);
+			}
+		}
+		/* There are readers, we have to wait */
+		return(RW_LOCK_WAIT_EX);
+
+		break;
+
+	    case RW_LOCK_EX:
+		/* already have x-lock */
+		if ((lock->pass == 0)&&(pass == 0)) {
+			__sync_fetch_and_add(&(lock->writer_count),1);
+
+#ifdef UNIV_SYNC_DEBUG
+			rw_lock_add_debug_info(lock, pass, RW_LOCK_EX, file_name,
+						line);
+#endif
+
+			lock->last_x_file_name = file_name;
+			lock->last_x_line = line;
+
+			/* Locking succeeded, we may return */
+			return(RW_LOCK_EX);
+		}
+
+		return(RW_LOCK_NOT_LOCKED);
+
+		break;
+
+	    default: /* ??? */
+		return(RW_LOCK_NOT_LOCKED);
+	}
+#else /* HAVE_GCC_ATOMIC_BUILTINS */
+
 	ut_ad(mutex_own(rw_lock_get_mutex(lock)));
 
 	if (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
@@ -447,6 +576,7 @@ rw_lock_x_lock_low(
 		/* Locking succeeded, we may return */
 		return(RW_LOCK_EX);
 	}
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
 
 	/* Locking did not succeed */
 	return(RW_LOCK_NOT_LOCKED);
@@ -472,19 +602,33 @@ rw_lock_x_lock_func(
 	ulint		line)	/* in: line where requested */
 {
 	ulint	index;	/* index of the reserved wait cell */
-	ulint	state;	/* lock state acquired */
+	ulint	state = RW_LOCK_NOT_LOCKED;	/* lock state acquired */
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	ulint	prev_state = RW_LOCK_NOT_LOCKED;
+#endif
 	ulint	i;	/* spin round count */
 
 	ut_ad(rw_lock_validate(lock));
 
 lock_loop:
+	i = 0;
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	prev_state = state;
+#else
 	/* Acquire the mutex protecting the rw-lock fields */
 	mutex_enter_fast(&(lock->mutex));
+#endif
 
 	state = rw_lock_x_lock_low(lock, pass, file_name, line);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (state != prev_state) i=0; /* if progress, reset counter. */
+#else
 	mutex_exit(&(lock->mutex));
+#endif
 
+spin_loop:
 	if (state == RW_LOCK_EX) {
 
 		return;	/* Locking succeeded */
@@ -492,10 +636,9 @@ rw_lock_x_lock_func(
 	} else if (state == RW_LOCK_NOT_LOCKED) {
 
 		/* Spin waiting for the writer field to become free */
-		i = 0;
 
-		while (rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED
-		       && i < SYNC_SPIN_ROUNDS) {
+		while (i < SYNC_SPIN_ROUNDS
+		       && rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED) {
 			if (srv_spin_wait_delay) {
 				ut_delay(ut_rnd_interval(0,
 							 srv_spin_wait_delay));
@@ -509,9 +652,12 @@ rw_lock_x_lock_func(
 	} else if (state == RW_LOCK_WAIT_EX) {
 
 		/* Spin waiting for the reader count field to become zero */
-		i = 0;
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+		while (lock->lock_word != RW_LOCK_BIAS
+#else
 		while (rw_lock_get_reader_count(lock) != 0
+#endif
 		       && i < SYNC_SPIN_ROUNDS) {
 			if (srv_spin_wait_delay) {
 				ut_delay(ut_rnd_interval(0,
@@ -524,7 +670,6 @@ rw_lock_x_lock_func(
 			os_thread_yield();
 		}
 	} else {
-		i = 0; /* Eliminate a compiler warning */
 		ut_error;
 	}
 
@@ -541,34 +686,69 @@ rw_lock_x_lock_func(
 	/* We try once again to obtain the lock. Acquire the mutex protecting
 	the rw-lock fields */
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	prev_state = state;
+#else
 	mutex_enter(rw_lock_get_mutex(lock));
+#endif
 
 	state = rw_lock_x_lock_low(lock, pass, file_name, line);
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	if (state != prev_state) i=0; /* if progress, reset counter. */
+#endif
+
 	if (state == RW_LOCK_EX) {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 		return;	/* Locking succeeded */
 	}
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	/* like sync0sync.c doing */
+	i++;
+
+	if (i < SYNC_SPIN_ROUNDS) {
+		goto spin_loop;
+	}
+#endif
+
 	rw_x_system_call_count++;
 
 	sync_array_reserve_cell(sync_primary_wait_array,
 				lock,
-#ifdef __WIN__
-				/* On windows RW_LOCK_WAIT_EX signifies
-				that this thread should wait on the
-				special wait_ex_event. */
 				(state == RW_LOCK_WAIT_EX)
 				 ? RW_LOCK_WAIT_EX :
-#endif
 				RW_LOCK_EX,
 				file_name, line,
 				&index);
 
-	rw_lock_set_waiters(lock, 1);
+	if (state == RW_LOCK_WAIT_EX) {
+		rw_lock_set_wx_waiters(lock, 1);
+	} else {
+		rw_lock_set_x_waiters(lock, 1);
+	}
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	/* like sync0sync.c doing */
+	for (i = 0; i < 4; i++) {
+		prev_state = state;
+		state = rw_lock_x_lock_low(lock, pass, file_name, line);
+		if (state == RW_LOCK_EX) {
+			sync_array_free_cell(sync_primary_wait_array, index);
+			return; /* Locking succeeded */
+		}
+		if (state != prev_state) {
+			/* retry! */
+			sync_array_free_cell(sync_primary_wait_array, index);
+			goto lock_loop;
+		}
+	}
+#else
 	mutex_exit(rw_lock_get_mutex(lock));
+#endif
 
 	if (srv_print_latch_waits) {
 		fprintf(stderr,
@@ -730,7 +910,9 @@ rw_lock_own(
 	ut_ad(lock);
 	ut_ad(rw_lock_validate(lock));
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(&(lock->mutex));
+#endif
 
 	info = UT_LIST_GET_FIRST(lock->debug_list);
 
@@ -740,7 +922,9 @@ rw_lock_own(
 		    && (info->pass == 0)
 		    && (info->lock_type == lock_type)) {
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 			mutex_exit(&(lock->mutex));
+#endif
 			/* Found! */
 
 			return(TRUE);
@@ -748,7 +932,9 @@ rw_lock_own(
 
 		info = UT_LIST_GET_NEXT(list, info);
 	}
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(&(lock->mutex));
+#endif
 
 	return(FALSE);
 }
@@ -770,21 +956,25 @@ rw_lock_is_locked(
 	ut_ad(lock);
 	ut_ad(rw_lock_validate(lock));
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_enter(&(lock->mutex));
+#endif
 
 	if (lock_type == RW_LOCK_SHARED) {
 		if (lock->reader_count > 0) {
 			ret = TRUE;
 		}
 	} else if (lock_type == RW_LOCK_EX) {
-		if (lock->writer == RW_LOCK_EX) {
+		if (rw_lock_get_writer(lock) == RW_LOCK_EX) {
 			ret = TRUE;
 		}
 	} else {
 		ut_error;
 	}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 	mutex_exit(&(lock->mutex));
+#endif
 
 	return(ret);
 }
@@ -814,16 +1004,26 @@ rw_lock_list_print_info(
 
 		count++;
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_enter(&(lock->mutex));
+#endif
 
 		if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
 		    || (rw_lock_get_reader_count(lock) != 0)
-		    || (rw_lock_get_waiters(lock) != 0)) {
+		    || (rw_lock_get_s_waiters(lock) != 0)
+		    || (rw_lock_get_x_waiters(lock) != 0)
+		    || (rw_lock_get_wx_waiters(lock) != 0)) {
 
 			fprintf(file, "RW-LOCK: %p ", (void*) lock);
 
-			if (rw_lock_get_waiters(lock)) {
-				fputs(" Waiters for the lock exist\n", file);
+			if (rw_lock_get_s_waiters(lock)) {
+				fputs(" s_waiters for the lock exist,", file);
+			}
+			if (rw_lock_get_x_waiters(lock)) {
+				fputs(" x_waiters for the lock exist\n", file);
+			}
+			if (rw_lock_get_wx_waiters(lock)) {
+				fputs(" wait_ex_waiters for the lock exist\n", file);
 			} else {
 				putc('\n', file);
 			}
@@ -835,7 +1035,9 @@ rw_lock_list_print_info(
 			}
 		}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(&(lock->mutex));
+#endif
 		lock = UT_LIST_GET_NEXT(list, lock);
 	}
 
@@ -860,10 +1062,18 @@ rw_lock_print(
 
 	if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
 	    || (rw_lock_get_reader_count(lock) != 0)
-	    || (rw_lock_get_waiters(lock) != 0)) {
+	    || (rw_lock_get_s_waiters(lock) != 0)
+	    || (rw_lock_get_x_waiters(lock) != 0)
+	    || (rw_lock_get_wx_waiters(lock) != 0)) {
 
-		if (rw_lock_get_waiters(lock)) {
-			fputs(" Waiters for the lock exist\n", stderr);
+		if (rw_lock_get_s_waiters(lock)) {
+			fputs(" s_waiters for the lock exist,", stderr);
+		}
+		if (rw_lock_get_x_waiters(lock)) {
+			fputs(" x_waiters for the lock exist\n", stderr);
+		}
+		if (rw_lock_get_wx_waiters(lock)) {
+			fputs(" wait_ex_waiters for the lock exist\n", stderr);
 		} else {
 			putc('\n', stderr);
 		}
@@ -922,14 +1132,18 @@ rw_lock_n_locked(void)
 	lock = UT_LIST_GET_FIRST(rw_lock_list);
 
 	while (lock != NULL) {
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_enter(rw_lock_get_mutex(lock));
+#endif
 
 		if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
 		    || (rw_lock_get_reader_count(lock) != 0)) {
 			count++;
 		}
 
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(rw_lock_get_mutex(lock));
+#endif
 		lock = UT_LIST_GET_NEXT(list, lock);
 	}