Google SMP patch

storage/innobase/btr/btr0cur.c

@@ -333,7 +333,7 @@ btr_cur_search_to_nth_level(
 #ifdef UNIV_SEARCH_PERF_STAT
 	info->n_searches++;
 #endif
-	if (btr_search_latch.writer == RW_LOCK_NOT_LOCKED
+	if (rw_lock_get_writer(&btr_search_latch) == RW_LOCK_NOT_LOCKED
 	    && latch_mode <= BTR_MODIFY_LEAF && info->last_hash_succ
 	    && !estimate
 #ifdef PAGE_CUR_LE_OR_EXTENDS

storage/innobase/btr/btr0sea.c

@@ -748,8 +748,8 @@ btr_search_guess_on_hash(
 		rw_lock_s_lock(&btr_search_latch);
 	}
 
-	ut_ad(btr_search_latch.writer != RW_LOCK_EX);
+	ut_ad(rw_lock_get_writer(&btr_search_latch) != RW_LOCK_EX);
-	ut_ad(btr_search_latch.reader_count > 0);
+	ut_ad(rw_lock_get_reader_count(&btr_search_latch) > 0);
 
 	rec = ha_search_and_get_data(btr_search_sys->hash_index, fold);
 

storage/innobase/buf/buf0buf.c

@@ -1277,8 +1277,8 @@ loop:
 
 	if (mode == BUF_GET_NOWAIT) {
 		if (rw_latch == RW_S_LATCH) {
-			success = rw_lock_s_lock_func_nowait(&(block->lock),
+			success = rw_lock_s_lock_nowait(&(block->lock),
-							     file, line);
+							file, line);
 			fix_type = MTR_MEMO_PAGE_S_FIX;
 		} else {
 			ut_ad(rw_latch == RW_X_LATCH);
@@ -1403,8 +1403,8 @@ buf_page_optimistic_get_func(
 	ut_ad(!ibuf_inside() || ibuf_page(block->space, block->offset));
 
 	if (rw_latch == RW_S_LATCH) {
-		success = rw_lock_s_lock_func_nowait(&(block->lock),
+		success = rw_lock_s_lock_nowait(&(block->lock),
-						     file, line);
+						file, line);
 		fix_type = MTR_MEMO_PAGE_S_FIX;
 	} else {
 		success = rw_lock_x_lock_func_nowait(&(block->lock),
@@ -1534,8 +1534,8 @@ buf_page_get_known_nowait(
 	ut_ad(!ibuf_inside() || (mode == BUF_KEEP_OLD));
 
 	if (rw_latch == RW_S_LATCH) {
-		success = rw_lock_s_lock_func_nowait(&(block->lock),
+		success = rw_lock_s_lock_nowait(&(block->lock),
-						     file, line);
+						file, line);
 		fix_type = MTR_MEMO_PAGE_S_FIX;
 	} else {
 		success = rw_lock_x_lock_func_nowait(&(block->lock),

storage/innobase/handler/ha_innodb.cc

@@ -374,6 +374,10 @@ static SHOW_VAR innodb_status_variables[]= {
   (char*) &export_vars.innodb_dblwr_pages_written,	  SHOW_LONG},
   {"dblwr_writes",
   (char*) &export_vars.innodb_dblwr_writes,		  SHOW_LONG},
+  {"have_atomic_builtins",
+  (char*) &export_vars.innodb_have_atomic_builtins,	  SHOW_BOOL},
+  {"heap_enabled",
+  (char*) &export_vars.innodb_heap_enabled,		  SHOW_BOOL},
   {"log_waits",
   (char*) &export_vars.innodb_log_waits,		  SHOW_LONG},
   {"log_write_requests",
@@ -6878,6 +6882,7 @@ innodb_mutex_show_status(
 {
 	char buf1[IO_SIZE], buf2[IO_SIZE];
 	mutex_t*  mutex;
+	rw_lock_t* lock;
 #ifdef UNIV_DEBUG
 	ulint	  rw_lock_count= 0;
 	ulint	  rw_lock_count_spin_loop= 0;
@@ -6948,6 +6953,31 @@ innodb_mutex_show_status(
 
 	mutex_exit_noninline(&mutex_list_mutex);
 
+	mutex_enter_noninline(&rw_lock_list_mutex);
+
+	lock = UT_LIST_GET_FIRST(rw_lock_list);
+
+	while (lock != NULL)
+	{
+		if (lock->count_os_wait)
+		{
+			buf1len= my_snprintf(buf1, sizeof(buf1), "%s:%lu",
+                                    lock->cfile_name, (ulong) lock->cline);
+			buf2len= my_snprintf(buf2, sizeof(buf2),
+                                    "os_waits=%lu", lock->count_os_wait);
+
+			if (stat_print(thd, innobase_hton_name,
+				       hton_name_len, buf1, buf1len,
+				       buf2, buf2len)) {
+				mutex_exit_noninline(&rw_lock_list_mutex);
+				DBUG_RETURN(1);
+			}
+		}
+		lock = UT_LIST_GET_NEXT(list, lock);
+	}
+
+	mutex_exit_noninline(&rw_lock_list_mutex);
+
 #ifdef UNIV_DEBUG
 	buf2len= my_snprintf(buf2, sizeof(buf2),
 		"count=%lu, spin_waits=%lu, spin_rounds=%lu, "
@@ -6980,6 +7010,7 @@ bool innobase_show_status(handlerton *hton, THD* thd,
 		return FALSE;
 	}
 }
+	rw_lock_t* lock;
 
 
 /****************************************************************************

storage/innobase/include/buf0buf.ic

@@ -513,7 +513,7 @@ buf_block_buf_fix_inc_debug(
 {
 	ibool	ret;
 
-	ret = rw_lock_s_lock_func_nowait(&(block->debug_latch), file, line);
+	ret = rw_lock_s_lock_nowait(&(block->debug_latch), file, line);
 
 	ut_ad(ret == TRUE);
 	ut_ad(mutex_own(&block->mutex));

storage/innobase/include/os0sync.h

@@ -261,6 +261,29 @@ os_fast_mutex_free(
 /*===============*/
 	os_fast_mutex_t*	fast_mutex);	/* in: mutex to free */
 
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+/**************************************************************
+Atomic compare-and-swap for InnoDB. Currently requires GCC atomic builtins. */
+UNIV_INLINE
+ibool
+os_compare_and_swap(
+/*================*/
+						/* out: true if swapped */
+	volatile lint*		ptr,		/* in: pointer to target */
+	lint			oldVal,		/* in: value to compare to */
+	lint			newVal);	/* in: value to swap in */
+/**************************************************************
+Atomic increment for InnoDB. Currently requires GCC atomic builtins. */
+UNIV_INLINE
+lint
+os_atomic_increment(
+/*================*/
+						/* out: resulting value */
+	volatile lint*		ptr,		/* in: pointer to target */
+	lint			amount);	/* in: amount of increment */
+
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
+
 #ifndef UNIV_NONINL
 #include "os0sync.ic"
 #endif

storage/innobase/include/os0sync.ic

@@ -44,3 +44,38 @@ os_fast_mutex_trylock(
 #endif
 #endif
 }
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+/**************************************************************
+Atomic compare-and-swap for InnoDB. Currently requires GCC atomic builtins. */
+UNIV_INLINE
+ibool
+os_compare_and_swap(
+/*================*/
+					/* out: true if swapped */
+	volatile lint* 	ptr,		/* in: pointer to target */
+	lint		oldVal,		/* in: value to compare to */
+	lint		newVal)		/* in: value to swap in */
+{
+	if(__sync_bool_compare_and_swap(ptr, oldVal, newVal)) {
+		return(TRUE);
+	}
+
+	return(FALSE);
+}
+
+/**************************************************************
+Atomic increment for InnoDB. Currently requires GCC atomic builtins. */
+UNIV_INLINE
+lint
+os_atomic_increment(
+/*================*/
+					/* out: resulting value */
+	volatile lint*	ptr,		/* in: pointer to target */
+	lint		amount)		/* in: amount of increment */
+{
+	lint newVal = __sync_add_and_fetch(ptr, amount);
+	return newVal;
+}
+
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */

storage/innobase/include/srv0srv.h

@@ -513,6 +513,8 @@ struct export_var_struct{
 	ulint innodb_buffer_pool_read_ahead_rnd;
 	ulint innodb_dblwr_pages_written;
 	ulint innodb_dblwr_writes;
+	ibool innodb_have_atomic_builtins;
+	ibool innodb_heap_enabled;
 	ulint innodb_log_waits;
 	ulint innodb_log_write_requests;
 	ulint innodb_log_writes;
@@ -549,4 +551,3 @@ struct srv_sys_struct{
 extern ulint	srv_n_threads_active[];
 
 #endif
-

storage/innobase/include/sync0rw.h

@@ -24,6 +24,12 @@ smaller than 30 and the order of the numerical values like below! */
 #define	RW_X_LATCH	2
 #define	RW_NO_LATCH	3
 
+/* We decrement lock_word by this amount for each x_lock. It is also the
+start value for the lock_word, meaning that it limits the maximum number
+of concurrent read locks before the rw_lock breaks. The current value of
+0x00100000 allows 1,048,575 concurrent readers and 2047 recursive writers.*/
+#define X_LOCK_DECR		0x00100000
+
 typedef struct rw_lock_struct		rw_lock_t;
 #ifdef UNIV_SYNC_DEBUG
 typedef struct rw_lock_debug_struct	rw_lock_debug_t;
@@ -47,14 +53,14 @@ extern ibool		rw_lock_debug_waiters;	/* This is set to TRUE, if
 					there may be waiters for the event */
 #endif /* UNIV_SYNC_DEBUG */
 
-extern	ulint	rw_s_system_call_count;
+extern	ib_longlong	rw_s_spin_wait_count;
-extern	ulint	rw_s_spin_wait_count;
+extern	ib_longlong	rw_s_spin_round_count;
-extern	ulint	rw_s_exit_count;
+extern	ib_longlong	rw_s_exit_count;
-extern	ulint	rw_s_os_wait_count;
+extern	ib_longlong	rw_s_os_wait_count;
-extern	ulint	rw_x_system_call_count;
+extern	ib_longlong	rw_x_spin_wait_count;
-extern	ulint	rw_x_spin_wait_count;
+extern	ib_longlong	rw_x_spin_round_count;
-extern	ulint	rw_x_os_wait_count;
+extern	ib_longlong	rw_x_os_wait_count;
-extern	ulint	rw_x_exit_count;
+extern	ib_longlong	rw_x_exit_count;
 
 /**********************************************************************
 Creates, or rather, initializes an rw-lock object in a specified memory
@@ -127,8 +133,8 @@ corresponding function. */
 NOTE! The following macros should be used in rw s-locking, not the
 corresponding function. */
 
-#define rw_lock_s_lock_nowait(M)	rw_lock_s_lock_func_nowait(\
+#define rw_lock_s_lock_nowait(M, F, L)    rw_lock_s_lock_low(\
-		(M), __FILE__, __LINE__)
+					  (M), 0, (F), (L))
 /**********************************************************************
 NOTE! Use the corresponding macro, not directly this function, except if
 you supply the file name and line number. Lock an rw-lock in shared mode
@@ -146,18 +152,6 @@ rw_lock_s_lock_func(
 	const char*	file_name,/* in: file name where lock requested */
 	ulint		line);	/* in: line where requested */
 /**********************************************************************
-NOTE! Use the corresponding macro, not directly this function, except if
-you supply the file name and line number. Lock an rw-lock in shared mode
-for the current thread if the lock can be acquired immediately. */
-UNIV_INLINE
-ibool
-rw_lock_s_lock_func_nowait(
-/*=======================*/
-				/* out: TRUE if success */
-	rw_lock_t*	lock,	/* in: pointer to rw-lock */
-	const char*	file_name,/* in: file name where lock requested */
-	ulint		line);	/* in: line where requested */
-/**********************************************************************
 NOTE! Use the corresponding macro, not directly this function! Lock an
 rw-lock in exclusive mode for the current thread if the lock can be
 obtained immediately. */
@@ -341,6 +335,23 @@ ulint
 rw_lock_get_reader_count(
 /*=====================*/
 	rw_lock_t*	lock);
+/**********************************************************************
+Decrements lock_word the specified amount if it is greater than 0.
+This is used by both s_lock and x_lock operations. */
+UNIV_INLINE
+ibool
+rw_lock_lock_word_decr(
+					/* out: TRUE if decr occurs */
+	rw_lock_t*	lock,		/* in: rw-lock */
+	ulint		amount);	/* in: amount to decrement */
+/**********************************************************************
+Increments lock_word the specified amount and returns new value. */
+UNIV_INLINE
+lint
+rw_lock_lock_word_incr(
+					/* out: TRUE if decr occurs */
+	rw_lock_t*	lock,
+	ulint		amount);	/* in: rw-lock */
 #ifdef UNIV_SYNC_DEBUG
 /**********************************************************************
 Checks if the thread has locked the rw-lock in the specified mode, with
@@ -417,44 +428,28 @@ 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
 simultaneously in this lock, but only one writer may have an exclusive lock,
 in which case no shared locks are allowed. To prevent starving of a writer
-blocked by readers, a writer may queue for the lock by setting the writer
+blocked by readers, a writer may queue for x-lock by decrementing lock_word:
-field. Then no new readers are allowed in. */
+no new readers will be let in while the thread waits for readers to exit. */
 
 struct rw_lock_struct {
-	os_event_t	event;	/* Used by sync0arr.c for thread queueing */
+	volatile lint	lock_word;
-
+				/* Holds the state of the lock. */
-#ifdef __WIN__
+	volatile ulint	waiters;/* 1: there are waiters */
-	os_event_t	wait_ex_event;	/* This windows specific event is
+	volatile ulint	pass;	/* Default value 0. This is set to some
-				used by the thread which has set the
-				lock state to RW_LOCK_WAIT_EX. The
-				rw_lock design guarantees that this
-				thread will be the next one to proceed
-				once the current the event gets
-				signalled. See LEMMA 2 in sync0sync.c */
-#endif
-
-	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
-				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;
-				/* Thread id of a possible writer thread */
-	ulint	writer_count;	/* Number of times the same thread has
-				recursively locked the lock in the exclusive
-				mode */
-	mutex_t	mutex;		/* The mutex protecting rw_lock_struct */
-	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
+	volatile os_thread_id_t	writer_thread;
-				waiters (readers or writers) in the global
+				/* Thread id of writer thread */
-				wait array, waiting for this rw_lock.
+	os_event_t	event;	/* Used by sync0arr.c for thread queueing */
-				Otherwise, == 0. */
+	os_event_t	wait_ex_event;
+				/* Event for next-writer to wait on. A thread
+				must decrement lock_word before waiting. */
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
+	mutex_t	mutex;		/* The mutex protecting rw_lock_struct */
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
+
 	UT_LIST_NODE_T(rw_lock_t) list;
 				/* All allocated rw locks are put into a
 				list */
@@ -464,7 +459,9 @@ struct rw_lock_struct {
 				info list of the lock */
 	ulint	level;		/* Level in the global latching order. */
 #endif /* UNIV_SYNC_DEBUG */
+	ulint count_os_wait;	/* Count of os_waits. May not be accurate */
 	const char*	cfile_name;/* File name where lock created */
+        /* last s-lock file/line is not guaranteed to be correct */
 	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;

storage/innobase/include/sync0rw.ic

@@ -62,40 +62,48 @@ rw_lock_set_waiters(
 {
 	lock->waiters = flag;
 }
+
+/**********************************************************************
+Returns the write-status of the lock - this function made more sense
+with the old rw_lock implementation.
+ */
 UNIV_INLINE
 ulint
 rw_lock_get_writer(
 /*===============*/
 	rw_lock_t*	lock)
 {
-	return(lock->writer);
+	lint lock_word = lock->lock_word;
-}
+	if(lock_word > 0) {
-UNIV_INLINE
+		/* return NOT_LOCKED in s-lock state, like the writer
-void
+		member of the old lock implementation. */
-rw_lock_set_writer(
+		return RW_LOCK_NOT_LOCKED;
-/*===============*/
+	} else if (((-lock_word) % X_LOCK_DECR) == 0) {
-	rw_lock_t*	lock,
+		return RW_LOCK_EX;
-	ulint		flag)
+	} else {
-{
+                ut_ad(lock_word > -X_LOCK_DECR);
-	lock->writer = flag;
+		return RW_LOCK_WAIT_EX;
+	}
 }
+
 UNIV_INLINE
 ulint
 rw_lock_get_reader_count(
 /*=====================*/
 	rw_lock_t*	lock)
 {
-	return(lock->reader_count);
+	lint lock_word = lock->lock_word;
-}
+	if(lock_word > 0) {
-UNIV_INLINE
+		/* s-locked, no x-waiters */
-void
+		return(X_LOCK_DECR - lock_word);
-rw_lock_set_reader_count(
+	} else if (lock_word < 0 && lock_word > -X_LOCK_DECR) {
-/*=====================*/
+		/* s-locked, with x-waiters */
-	rw_lock_t*	lock,
+		return (ulint)(-lock_word);
-	ulint		count)
+	}
-{
+	return 0;
-	lock->reader_count = count;
 }
+
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 UNIV_INLINE
 mutex_t*
 rw_lock_get_mutex(
@@ -104,6 +112,7 @@ rw_lock_get_mutex(
 {
 	return(&(lock->mutex));
 }
+#endif
 
 /**********************************************************************
 Returns the value of writer_count for the lock. Does not reserve the lock
@@ -115,7 +124,87 @@ rw_lock_get_x_lock_count(
 				/* out: value of writer_count */
 	rw_lock_t*	lock)	/* in: rw-lock */
 {
-	return(lock->writer_count);
+	lint lock_copy = lock->lock_word;
+	/* If there is a reader, lock_word is not divisible by X_LOCK_DECR */
+	if(lock_copy > 0 || (-lock_copy) % X_LOCK_DECR != 0) {
+		return 0;
+	}
+	return ((-lock_copy) / X_LOCK_DECR) + 1;
+}
+
+/**********************************************************************
+Two different implementations for decrementing the lock_word of a rw_lock:
+one for systems supporting atomic operations, one for others. This does
+does not support recusive x-locks: they should be handled by the caller and
+need not be atomic since they are performed by the current lock holder.
+Returns true if the decrement was made, false if not. */
+UNIV_INLINE
+ibool
+rw_lock_lock_word_decr(
+				/* out: TRUE if decr occurs */
+	rw_lock_t*	lock,	/* in: rw-lock */
+	ulint		amount)	/* in: amount of decrement */
+{
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+
+        lint local_lock_word = lock->lock_word;
+	while (local_lock_word > 0) {
+		if(os_compare_and_swap(&(lock->lock_word),
+                                       local_lock_word,
+                                       local_lock_word - amount)) {
+			return TRUE;
+		}
+		local_lock_word = lock->lock_word;
+	}
+	return(FALSE);
+
+#else /* HAVE_GCC_ATOMIC_BUILTINS */
+
+	ibool success = FALSE;
+	mutex_enter(&(lock->mutex));
+	if(lock->lock_word > 0) {
+		lock->lock_word -= amount;
+		success = TRUE;
+	}
+	mutex_exit(&(lock->mutex));
+	return success;
+
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
+
+}
+
+/**********************************************************************
+Two different implementations for incrementing the lock_word of a rw_lock:
+one for systems supporting atomic operations, one for others.
+Returns the value of lock_word after increment. */
+UNIV_INLINE
+lint
+rw_lock_lock_word_incr(
+				/* out: lock->lock_word after increment */
+	rw_lock_t*	lock,	/* in: rw-lock */
+	ulint		amount)	/* in: amount of increment */
+{
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+
+	return(os_atomic_increment(&(lock->lock_word), amount));
+
+#else /* HAVE_GCC_ATOMIC_BUILTINS */
+
+	lint local_lock_word;
+
+	mutex_enter(&(lock->mutex));
+
+	lock->lock_word += amount;
+	local_lock_word = lock->lock_word;
+
+	mutex_exit(&(lock->mutex));
+
+        return local_lock_word;
+
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
+
 }
 
 /**********************************************************************
@@ -133,25 +222,21 @@ rw_lock_s_lock_low(
 	const char*	file_name, /* in: file name where lock requested */
 	ulint		line)	/* in: line where requested */
 {
-	ut_ad(mutex_own(rw_lock_get_mutex(lock)));
+	/* TODO: study performance of UNIV_LIKELY branch prediction hints. */
-
+	if (!rw_lock_lock_word_decr(lock, 1)) {
-	/* Check if the writer field is free */
+		/* Locking did not succeed */
-
+		return(FALSE);
-	if (UNIV_LIKELY(lock->writer == RW_LOCK_NOT_LOCKED)) {
-		/* Set the shared lock by incrementing the reader count */
-		lock->reader_count++;
-
-#ifdef UNIV_SYNC_DEBUG
-		rw_lock_add_debug_info(lock, pass, RW_LOCK_SHARED, file_name,
-				       line);
-#endif
-		lock->last_s_file_name = file_name;
-		lock->last_s_line = line;
-
-		return(TRUE);	/* locking succeeded */
 	}
 
-	return(FALSE);	/* locking did not succeed */
+#ifdef UNIV_SYNC_DEBUG
+	rw_lock_add_debug_info(lock, pass, RW_LOCK_SHARED, file_name, line);
+#endif
+	/* These debugging values are not set safely: they may be incorrect
+        or even refer to a line that is invalid for the file name. */
+	lock->last_s_file_name = file_name;
+	lock->last_s_line = line;
+
+	return(TRUE);	/* locking succeeded */
 }
 
 /**********************************************************************
@@ -166,11 +251,10 @@ 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(lock->lock_word == X_LOCK_DECR);
-	ut_ad(rw_lock_get_reader_count(lock) == 0);
 
-	/* Set the shared lock by incrementing the reader count */
+	/* Indicate there is a new reader by decrementing lock_word */
-	lock->reader_count++;
+	lock->lock_word--;
 
 	lock->last_s_file_name = file_name;
 	lock->last_s_line = line;
@@ -193,12 +277,10 @@ rw_lock_x_lock_direct(
 	ulint		line)		/* in: line where lock requested */
 {
 	ut_ad(rw_lock_validate(lock));
-	ut_ad(rw_lock_get_reader_count(lock) == 0);
+	ut_ad(lock->lock_word == X_LOCK_DECR);
-	ut_ad(rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED);
 
-	rw_lock_set_writer(lock, RW_LOCK_EX);
+	lock->lock_word -= X_LOCK_DECR;
 	lock->writer_thread = os_thread_get_curr_id();
-	lock->writer_count++;
 	lock->pass = 0;
 
 	lock->last_x_file_name = file_name;
@@ -240,15 +322,12 @@ rw_lock_s_lock_func(
 	ut_ad(!rw_lock_own(lock, RW_LOCK_SHARED)); /* see NOTE above */
 #endif /* UNIV_SYNC_DEBUG */
 
-	mutex_enter(rw_lock_get_mutex(lock));
+	/* TODO: study performance of UNIV_LIKELY branch prediction hints. */
-
+	if (rw_lock_s_lock_low(lock, pass, file_name, line)) {
-	if (UNIV_LIKELY(rw_lock_s_lock_low(lock, pass, file_name, line))) {
-		mutex_exit(rw_lock_get_mutex(lock));
 
 		return; /* Success */
 	} else {
 		/* Did not succeed, try spin wait */
-		mutex_exit(rw_lock_get_mutex(lock));
 
 		rw_lock_s_lock_spin(lock, pass, file_name, line);
 
@@ -256,43 +335,6 @@ rw_lock_s_lock_func(
 	}
 }
 
-/**********************************************************************
-NOTE! Use the corresponding macro, not directly this function! Lock an
-rw-lock in shared mode for the current thread if the lock can be acquired
-immediately. */
-UNIV_INLINE
-ibool
-rw_lock_s_lock_func_nowait(
-/*=======================*/
-				/* out: TRUE if success */
-	rw_lock_t*	lock,	/* in: pointer to rw-lock */
-	const char*	file_name,/* in: file name where lock requested */
-	ulint		line)	/* in: line where requested */
-{
-	ibool	success	= FALSE;
-
-	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++;
-
-#ifdef UNIV_SYNC_DEBUG
-		rw_lock_add_debug_info(lock, 0, RW_LOCK_SHARED, file_name,
-				       line);
-#endif
-
-		lock->last_s_file_name = file_name;
-		lock->last_s_line = line;
-
-		success = TRUE;
-	}
-
-	mutex_exit(rw_lock_get_mutex(lock));
-
-	return(success);
-}
-
 /**********************************************************************
 NOTE! Use the corresponding macro, not directly this function! Lock an
 rw-lock in exclusive mode for the current thread if the lock can be
@@ -306,38 +348,55 @@ rw_lock_x_lock_func_nowait(
 	const char*	file_name,/* in: file name where lock requested */
 	ulint		line)	/* in: line where requested */
 {
-	ibool		success		= FALSE;
 	os_thread_id_t	curr_thread	= os_thread_get_curr_id();
-	mutex_enter(rw_lock_get_mutex(lock));
 
-	if (UNIV_UNLIKELY(rw_lock_get_reader_count(lock) != 0)) {
+	ibool success;
-	} else if (UNIV_LIKELY(rw_lock_get_writer(lock)
+
-			       == RW_LOCK_NOT_LOCKED)) {
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
-		rw_lock_set_writer(lock, RW_LOCK_EX);
+	success = os_compare_and_swap(&(lock->lock_word), X_LOCK_DECR, 0);
+#else
+
+	success = FALSE;
+	mutex_enter(&(lock->mutex));
+	if(lock->lock_word == X_LOCK_DECR) {
+		lock->lock_word = 0;
+		success = TRUE;
+	}
+	mutex_exit(&(lock->mutex));
+
+#endif
+	if(success) {
 		lock->writer_thread = curr_thread;
 		lock->pass = 0;
-relock:
-		lock->writer_count++;
 
+	} else if (!(lock->pass) &&
+		   os_thread_eq(lock->writer_thread, curr_thread)) {
+		/* Must verify pass first: otherwise another thread can
+		call move_ownership suddenly allowing recursive locks.
+		and after we have verified our thread_id matches
+		(though move_ownership has since changed it).*/
+
+		/* Relock: this lock_word modification is safe since no other
+		threads can modify (lock, unlock, or reserve) lock_word while
+		there is an exclusive writer and this is the writer thread. */
+		lock->lock_word -= X_LOCK_DECR;
+
+		ut_ad(((-lock->lock_word) % X_LOCK_DECR) == 0);
+
+	} else {
+		/* Failure */
+		return(FALSE);
+	}
 #ifdef UNIV_SYNC_DEBUG
-		rw_lock_add_debug_info(lock, 0, RW_LOCK_EX, file_name, line);
+	rw_lock_add_debug_info(lock, 0, RW_LOCK_EX, file_name, line);
 #endif
 
-		lock->last_x_file_name = file_name;
+	lock->last_x_file_name = file_name;
-		lock->last_x_line = line;
+	lock->last_x_line = line;
-
-		success = TRUE;
-	} else if (rw_lock_get_writer(lock) == RW_LOCK_EX
-		   && lock->pass == 0
-		   && os_thread_eq(lock->writer_thread, curr_thread)) {
-		goto relock;
-	}
-
-	mutex_exit(rw_lock_get_mutex(lock));
 
 	ut_ad(rw_lock_validate(lock));
 
-	return(success);
+	return(TRUE);
 }
 
 /**********************************************************************
@@ -353,39 +412,21 @@ rw_lock_s_unlock_func(
 #endif
 	)
 {
-	mutex_t*	mutex	= &(lock->mutex);
+	ut_ad((lock->lock_word % X_LOCK_DECR) != 0);
-	ibool		sg	= FALSE;
-
-	/* Acquire the mutex protecting the rw-lock fields */
-	mutex_enter(mutex);
-
-	/* Reset the shared lock by decrementing the reader count */
-
-	ut_a(lock->reader_count > 0);
-	lock->reader_count--;
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, pass, RW_LOCK_SHARED);
 #endif
 
-	/* If there may be waiters and this was the last s-lock,
+	/* Increment lock_word to indicate 1 less reader */
-	signal the object */
+	if(rw_lock_lock_word_incr(lock, 1) == 0) {
 
-	if (UNIV_UNLIKELY(lock->waiters)
+		/* wait_ex waiter exists. It may not be asleep, but we signal
-	    && lock->reader_count == 0) {
+                anyway. We do not wake other waiters, because they can't
-		sg = TRUE;
+                exist without wait_ex waiter and wait_ex waiter goes first.*/
-
-		rw_lock_set_waiters(lock, 0);
-	}
-
-	mutex_exit(mutex);
-
-	if (UNIV_UNLIKELY(sg)) {
-#ifdef __WIN__
 		os_event_set(lock->wait_ex_event);
-#endif
-		os_event_set(lock->event);
 		sync_array_object_signalled(sync_primary_wait_array);
+
 	}
 
 	ut_ad(rw_lock_validate(lock));
@@ -404,16 +445,15 @@ rw_lock_s_unlock_direct(
 /*====================*/
 	rw_lock_t*	lock)	/* in: rw-lock */
 {
-	/* Reset the shared lock by decrementing the reader count */
+	ut_ad(lock->lock_word < X_LOCK_DECR);
-
-	ut_ad(lock->reader_count > 0);
-
-	lock->reader_count--;
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, 0, RW_LOCK_SHARED);
 #endif
 
+	/* Decrease reader count by incrementing lock_word */
+	lock->lock_word++;
+
 	ut_ad(!lock->waiters);
 	ut_ad(rw_lock_validate(lock));
 #ifdef UNIV_SYNC_PERF_STAT
@@ -434,42 +474,32 @@ rw_lock_x_unlock_func(
 #endif
 	)
 {
-	ibool	sg	= FALSE;
+	ut_ad((lock->lock_word % X_LOCK_DECR) == 0);
 
-	/* Acquire the mutex protecting the rw-lock fields */
+	/* Must reset writer_thread while we still have the lock.
-	mutex_enter(&(lock->mutex));
+	If we are not the last unlocker, we correct it later in the function,
-
+	which is harmless since we still hold the lock. */
-	/* Reset the exclusive lock if this thread no longer has an x-mode
+	/* TODO: are there any risks of a thread id == -1 on any platform? */
-	lock */
+        os_thread_id_t local_writer_thread = lock->writer_thread;
-
+	lock->writer_thread = -1;
-	ut_ad(lock->writer_count > 0);
-
-	lock->writer_count--;
-
-	if (lock->writer_count == 0) {
-		rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
-	}
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, pass, RW_LOCK_EX);
 #endif
 
-	/* If there may be waiters, signal the lock */
+	if(rw_lock_lock_word_incr(lock, X_LOCK_DECR) == X_LOCK_DECR) {
-	if (UNIV_UNLIKELY(lock->waiters)
+		/* Lock is now free. May have to signal read/write waiters.
-	    && lock->writer_count == 0) {
+                We do not need to signal wait_ex waiters, since they cannot
+                exist when there is a writer. */
+		if(lock->waiters) {
+			rw_lock_set_waiters(lock, 0);
+			os_event_set(lock->event);
+			sync_array_object_signalled(sync_primary_wait_array);
+		}
 
-		sg = TRUE;
+	} else {
-		rw_lock_set_waiters(lock, 0);
+		/* We still hold x-lock, so we correct writer_thread. */
-	}
+		lock->writer_thread = local_writer_thread;
-
-	mutex_exit(&(lock->mutex));
-
-	if (UNIV_UNLIKELY(sg)) {
-#ifdef __WIN__
-		os_event_set(lock->wait_ex_event);
-#endif
-		os_event_set(lock->event);
-		sync_array_object_signalled(sync_primary_wait_array);
 	}
 
 	ut_ad(rw_lock_validate(lock));
@@ -491,18 +521,14 @@ rw_lock_x_unlock_direct(
 	/* Reset the exclusive lock if this thread no longer has an x-mode
 	lock */
 
-	ut_ad(lock->writer_count > 0);
+	ut_ad((lock->lock_word % X_LOCK_DECR) == 0);
-
-	lock->writer_count--;
-
-	if (lock->writer_count == 0) {
-		rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
-	}
 
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_remove_debug_info(lock, 0, RW_LOCK_EX);
 #endif
 
+	lock->lock_word += X_LOCK_DECR;
+
 	ut_ad(!lock->waiters);
 	ut_ad(rw_lock_validate(lock));
 

storage/innobase/include/sync0sync.h

@@ -252,7 +252,7 @@ mutex_n_reserved(void);
 NOT to be used outside this module except in debugging! Gets the value
 of the lock word. */
 UNIV_INLINE
-ulint
+byte
 mutex_get_lock_word(
 /*================*/
 	const mutex_t*	mutex);	/* in: mutex */
@@ -471,9 +471,13 @@ implementation of a mutual exclusion semaphore. */
 
 struct mutex_struct {
 	os_event_t	event;	/* Used by sync0arr.c for the wait queue */
-	ulint	lock_word;	/* This ulint is the target of the atomic
+
-				test-and-set instruction in Win32 */
+ 	byte	lock_word;	/* This byte is the target of the atomic
-#if !defined(_WIN32) || !defined(UNIV_CAN_USE_X86_ASSEMBLER)
+ 				test-and-set instruction in Win32 and
+ 				x86 32/64 with GCC 4.1.0 or later version */
+#if defined(_WIN32) && defined(UNIV_CAN_USE_X86_ASSEMBLER)
+#elif defined(HAVE_GCC_ATOMIC_BUILTINS)
+#else
 	os_fast_mutex_t
 		os_fast_mutex;	/* In other systems we use this OS mutex
 				in place of lock_word */
@@ -526,8 +530,7 @@ to 20 microseconds. */
 /* The number of system calls made in this module. Intended for performance
 monitoring. */
 
-extern	ulint	mutex_system_call_count;
+extern	ib_longlong	mutex_exit_count;
-extern	ulint	mutex_exit_count;
 
 #ifdef UNIV_SYNC_DEBUG
 /* Latching order checks start when this is set TRUE */

storage/innobase/include/sync0sync.ic

@@ -6,16 +6,6 @@ Mutex, the basic synchronization primitive
 Created 9/5/1995 Heikki Tuuri
 *******************************************************/
 
-#if defined(not_defined) && defined(__GNUC__) && defined(UNIV_INTEL_X86)
-/* %z0: Use the size of operand %0 which in our case is *m to determine
-instruction size, it should end up as xchgl. "1" in the input constraint,
-says that "in" has to go in the same place as "out".*/
-#define TAS(m, in, out) \
-	asm volatile ("xchg%z0 %2, %0" \
-	: "=g" (*(m)), "=r" (out) \
-	: "1" (in))	/* Note: "1" here refers to "=r" (out) */
-#endif
-
 /**********************************************************************
 Sets the waiters field in a mutex. */
 
@@ -59,7 +49,7 @@ mutex_signal_object(
 Performs an atomic test-and-set instruction to the lock_word field of a
 mutex. */
 UNIV_INLINE
-ulint
+byte
 mutex_test_and_set(
 /*===============*/
 				/* out: the previous value of lock_word: 0 or
@@ -67,18 +57,18 @@ mutex_test_and_set(
 	mutex_t*	mutex)	/* in: mutex */
 {
 #if defined(_WIN32) && defined(UNIV_CAN_USE_X86_ASSEMBLER)
-	ulint	res;
+	byte	res;
-	ulint*	lw;		/* assembler code is used to ensure that
+	byte*	lw;		/* assembler code is used to ensure that
 				lock_word is loaded from memory */
 	ut_ad(mutex);
-	ut_ad(sizeof(ulint) == 4);
+	ut_ad(sizeof(byte) == 1);
 
 	lw = &(mutex->lock_word);
 
 	__asm	MOV	ECX, lw
 		__asm	MOV	EDX, 1
-		__asm	XCHG	EDX, DWORD PTR [ECX]
+		__asm	XCHG	DL, BYTE PTR [ECX]
-		__asm	MOV	res, EDX
+		__asm	MOV	res, DL
 
 		/* The fence below would prevent this thread from
 		reading the data structure protected by the mutex
@@ -98,12 +88,8 @@ mutex_test_and_set(
 		/* mutex_fence(); */
 
 		return(res);
-#elif defined(not_defined) && defined(__GNUC__) && defined(UNIV_INTEL_X86)
+#elif defined(HAVE_GCC_ATOMIC_BUILTINS)
-	ulint	res;
+	return __sync_lock_test_and_set(&(mutex->lock_word), 1);
-
-	TAS(&mutex->lock_word, 1, res);
-
-	return(res);
 #else
 	ibool	ret;
 
@@ -117,7 +103,7 @@ mutex_test_and_set(
 		mutex->lock_word = 1;
 	}
 
-	return(ret);
+	return((byte)ret);
 #endif
 }
 
@@ -131,7 +117,7 @@ mutex_reset_lock_word(
 	mutex_t*	mutex)	/* in: mutex */
 {
 #if defined(_WIN32) && defined(UNIV_CAN_USE_X86_ASSEMBLER)
-	ulint*	lw;		/* assembler code is used to ensure that
+	byte*	lw;		/* assembler code is used to ensure that
 				lock_word is loaded from memory */
 	ut_ad(mutex);
 
@@ -139,11 +125,12 @@ mutex_reset_lock_word(
 
 	__asm	MOV	EDX, 0
 		__asm	MOV	ECX, lw
-		__asm	XCHG	EDX, DWORD PTR [ECX]
+		__asm	XCHG	DL, BYTE PTR [ECX]
-#elif defined(not_defined) && defined(__GNUC__) && defined(UNIV_INTEL_X86)
+#elif defined(HAVE_GCC_ATOMIC_BUILTINS)
-	ulint	res;
+	/* In theory __sync_lock_release should be used to release the lock.
-
+	Unfortunately, it does not work properly alone. The workaround is
-	TAS(&mutex->lock_word, 0, res);
+	that more conservative __sync_lock_test_and_set is used instead. */
+	__sync_lock_test_and_set(&(mutex->lock_word), 0);
 #else
 	mutex->lock_word = 0;
 
@@ -154,12 +141,12 @@ mutex_reset_lock_word(
 /**********************************************************************
 Gets the value of the lock word. */
 UNIV_INLINE
-ulint
+byte
 mutex_get_lock_word(
 /*================*/
 	const mutex_t*	mutex)	/* in: mutex */
 {
-	const volatile ulint*	ptr;	/* declared volatile to ensure that
+	const volatile byte*	ptr;	/* declared volatile to ensure that
 					lock_word is loaded from memory */
 	ut_ad(mutex);
 

storage/innobase/include/univ.i

@@ -116,6 +116,9 @@ by one. */
 #define UNIV_SET_MEM_TO_ZERO
 #endif
 
+/* Use malloc instead of innodb additional memory pool (great with tcmalloc) */
+#define UNIV_DISABLE_MEM_POOL
+
 /*
 #define UNIV_SQL_DEBUG
 #define UNIV_LOG_DEBUG

storage/innobase/mem/mem0pool.c

@@ -329,6 +329,9 @@ mem_area_alloc(
 				minus MEM_AREA_EXTRA_SIZE */
 	mem_pool_t*	pool)	/* in: memory pool */
 {
+#ifdef UNIV_DISABLE_MEM_POOL
+        return malloc(size);
+#else /* UNIV_DISABLE_MEM_POOL */
 	mem_area_t*	area;
 	ulint		n;
 	ibool		ret;
@@ -407,6 +410,7 @@ mem_area_alloc(
 		       ut_2_exp(n) - MEM_AREA_EXTRA_SIZE);
 
 	return((void*)(MEM_AREA_EXTRA_SIZE + ((byte*)area)));
+#endif /* UNIV_DISABLE_MEM_POOL */
 }
 
 /************************************************************************
@@ -459,6 +463,9 @@ mem_area_free(
 				buffer */
 	mem_pool_t*	pool)	/* in: memory pool */
 {
+#ifdef UNIV_DISABLE_MEM_POOL
+        free(ptr);
+#else /* UNIV_DISABLE_MEM_POOL */
 	mem_area_t*	area;
 	mem_area_t*	buddy;
 	void*		new_ptr;
@@ -570,6 +577,7 @@ mem_area_free(
 	mutex_exit(&(pool->mutex));
 
 	ut_ad(mem_pool_validate(pool));
+#endif /* UNIV_DISABLE_MEM_POOL */
 }
 
 /************************************************************************

storage/innobase/row/row0sel.c

@@ -1248,7 +1248,7 @@ table_loop:
 			rw_lock_s_lock(&btr_search_latch);
 
 			search_latch_locked = TRUE;
-		} else if (btr_search_latch.writer_is_wait_ex) {
+		} else if (rw_lock_get_writer(&btr_search_latch) == RW_LOCK_WAIT_EX) {
 
 			/* There is an x-latch request waiting: release the
 			s-latch for a moment; as an s-latch here is often
@@ -3327,7 +3327,7 @@ row_search_for_mysql(
 	/* PHASE 0: Release a possible s-latch we are holding on the
 	adaptive hash index latch if there is someone waiting behind */
 
-	if (UNIV_UNLIKELY(btr_search_latch.writer != RW_LOCK_NOT_LOCKED)
+	if (UNIV_UNLIKELY(rw_lock_get_writer(&btr_search_latch) != RW_LOCK_NOT_LOCKED)
 	    && trx->has_search_latch) {
 
 		/* There is an x-latch request on the adaptive hash index:

storage/innobase/srv/srv0srv.c

@@ -1834,6 +1834,16 @@ srv_export_innodb_status(void)
 	export_vars.innodb_buffer_pool_pages_misc = buf_pool->max_size
 		- UT_LIST_GET_LEN(buf_pool->LRU)
 		- UT_LIST_GET_LEN(buf_pool->free);
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	export_vars.innodb_have_atomic_builtins = 1;
+#else
+	export_vars.innodb_have_atomic_builtins = 0;
+#endif
+#ifdef UNIV_DISABLE_MEM_POOL
+	export_vars.innodb_heap_enabled = 0;
+#else
+	export_vars.innodb_heap_enabled = 1;
+#endif
 	export_vars.innodb_page_size = UNIV_PAGE_SIZE;
 	export_vars.innodb_log_waits = srv_log_waits;
 	export_vars.innodb_os_log_written = srv_os_log_written;

storage/innobase/srv/srv0start.c

@@ -1062,6 +1062,16 @@ innobase_start_or_create_for_mysql(void)
 		return(DB_ERROR);
 	}
 
+#ifdef UNIV_DISABLE_MEM_POOL
+	fprintf(stderr,
+		"InnoDB: The InnoDB memory heap has been disabled.\n");
+#endif
+
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+	fprintf(stderr,
+		"InnoDB: Mutex and rw_lock use GCC atomic builtins.\n");
+#endif
+
 	/* Since InnoDB does not currently clean up all its internal data
 	structures in MySQL Embedded Server Library server_end(), we
 	print an error message if someone tries to start up InnoDB a

storage/innobase/sync/sync0arr.c

@@ -295,28 +295,25 @@ sync_array_validate(
 }
 
 /***********************************************************************
-Puts the cell event in reset state. */
+Returns the event that the thread owning the cell waits for. */
 static
-ib_longlong
+os_event_t
-sync_cell_event_reset(
+sync_cell_get_event(
-/*==================*/
+/*================*/
-				/* out: value of signal_count
+	sync_cell_t*   	cell) /* in: non-empty sync array cell */
-				at the time of reset. */
-	ulint		type,	/* in: lock type mutex/rw_lock */
-	void*		object) /* in: the rw_lock/mutex object */
 {
+	ulint type = cell->request_type;
+
 	if (type == SYNC_MUTEX) {
-		return(os_event_reset(((mutex_t *) object)->event));
+		return(((mutex_t *) cell->wait_object)->event);
-#ifdef __WIN__
 	} else if (type == RW_LOCK_WAIT_EX) {
-		return(os_event_reset(
+		return(((rw_lock_t *) cell->wait_object)->wait_ex_event);
-		       ((rw_lock_t *) object)->wait_ex_event));
+	} else { /* RW_LOCK_SHARED and RW_LOCK_EX wait on the same event */
-#endif
+		return(((rw_lock_t *) cell->wait_object)->event);
-	} else {
-		return(os_event_reset(((rw_lock_t *) object)->event));
 	}
 }
 
+
 /**********************************************************************
 Reserves a wait array cell for waiting for an object.
 The event of the cell is reset to nonsignalled state. */
@@ -332,6 +329,7 @@ sync_array_reserve_cell(
 	ulint*		index)	/* out: index of the reserved cell */
 {
 	sync_cell_t*	cell;
+	os_event_t      event;
 	ulint		i;
 
 	ut_a(object);
@@ -370,8 +368,8 @@ sync_array_reserve_cell(
 			/* Make sure the event is reset and also store
 			the value of signal_count at which the event
 			was reset. */
-			cell->signal_count = sync_cell_event_reset(type,
+                        event = sync_cell_get_event(cell);
-								object);
+			cell->signal_count = os_event_reset(event);
 
 			cell->reservation_time = time(NULL);
 
@@ -411,19 +409,7 @@ sync_array_wait_event(
 	ut_a(!cell->waiting);
 	ut_ad(os_thread_get_curr_id() == cell->thread);
 
-	if (cell->request_type == SYNC_MUTEX) {
+	event = sync_cell_get_event(cell);
-		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 {
-		event = ((rw_lock_t*) cell->wait_object)->event;
-	}
-
 		cell->waiting = TRUE;
 
 #ifdef UNIV_SYNC_DEBUG
@@ -462,6 +448,7 @@ sync_array_cell_print(
 	mutex_t*	mutex;
 	rw_lock_t*	rwlock;
 	ulint		type;
+	ulint		writer;
 
 	type = cell->request_type;
 
@@ -491,9 +478,7 @@ 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);
@@ -504,22 +489,25 @@ 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, waiters flag %lu, "
+                        "lock_word: %ld\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) rw_lock_get_reader_count(rwlock),
 			(ulong) rwlock->waiters,
+			rwlock->lock_word,
 			rwlock->last_s_file_name,
 			(ulong) rwlock->last_s_line,
 			rwlock->last_x_file_name,
@@ -778,28 +766,30 @@ sync_arr_cell_can_wake_up(
 			return(TRUE);
 		}
 
-	} else if (cell->request_type == RW_LOCK_EX
+	} else if (cell->request_type == RW_LOCK_EX) {
-		   || cell->request_type == RW_LOCK_WAIT_EX) {
 
 		lock = cell->wait_object;
 
-		if (rw_lock_get_reader_count(lock) == 0
+                /* X_LOCK_DECR is the unlocked state */
-		    && rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
+	    	if (lock->lock_word == X_LOCK_DECR) {
 
 			return(TRUE);
 		}
 
-		if (rw_lock_get_reader_count(lock) == 0
+        } else if (cell->request_type == RW_LOCK_WAIT_EX) {
-		    && rw_lock_get_writer(lock) == RW_LOCK_WAIT_EX
+
-		    && os_thread_eq(lock->writer_thread, cell->thread)) {
+	    	lock = cell->wait_object;
+
+                /* lock_word == 0 means all readers have left */
+	    	if (lock->lock_word == 0) {
 
 			return(TRUE);
 		}
-
 	} else if (cell->request_type == RW_LOCK_SHARED) {
 		lock = cell->wait_object;
 
-		if (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
+                /* lock_word > 0 means no writer or reserved writer */
+		if (lock->lock_word > 0) {
 
 			return(TRUE);
 		}
@@ -844,11 +834,15 @@ 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
 }
 
 /**************************************************************************
@@ -868,6 +862,7 @@ sync_arr_wake_threads_if_sema_free(void)
 	sync_cell_t*	cell;
 	ulint		count;
 	ulint		i;
+	os_event_t      event;
 
 	sync_array_enter(arr);
 
@@ -877,36 +872,20 @@ sync_arr_wake_threads_if_sema_free(void)
 	while (count < arr->n_reserved) {
 
 		cell = sync_array_get_nth_cell(arr, i);
+		i++;
 
-		if (cell->wait_object != NULL) {
+		if (cell->wait_object == NULL) {
-
+			continue;
+		}
 			count++;
 
 			if (sync_arr_cell_can_wake_up(cell)) {
 
-				if (cell->request_type == SYNC_MUTEX) {
+			event = sync_cell_get_event(cell);
-					mutex_t*	mutex;
 
-					mutex = cell->wait_object;
+			os_event_set(event);
-					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 {
-					rw_lock_t*	lock;
-
-					lock = cell->wait_object;
-					os_event_set(lock->event);
-				}
-			}
 		}
 
-		i++;
 	}
 
 	sync_array_exit(arr);
@@ -1026,4 +1005,3 @@ sync_array_print_info(
 
 	sync_array_exit(arr);
 }
-

storage/innobase/sync/sync0rw.c

@@ -15,35 +15,111 @@ Created 9/11/1995 Heikki Tuuri
 #include "mem0mem.h"
 #include "srv0srv.h"
 
-/* number of system calls made during shared latching */
+/*
-ulint	rw_s_system_call_count	= 0;
+	IMPLEMENTATION OF THE RW_LOCK
+	=============================
+The status of a rw_lock is held in lock_word. The initial value of lock_word is
+X_LOCK_DECR. lock_word is decremented by 1 for each s-lock and by X_LOCK_DECR
+for each x-lock. This describes the lock state for each value of lock_word:
+ 
+lock_word == X_LOCK_DECR:      Unlocked.
+0 < lock_word < X_LOCK_DECR:   Read locked, no waiting writers.
+ 			       (X_LOCK_DECR - lock_word) is the
+ 			       number of readers that hold the lock.
+lock_word == 0:		       Write locked
+-X_LOCK_DECR < lock_word < 0:  Read locked, with a waiting writer.
+ 			       (-lock_word) is the number of readers
+ 			       that hold the lock.
+lock_word <= -X_LOCK_DECR:     Recursively write locked. lock_word has been
+ 			       decremented by X_LOCK_DECR once for each lock,
+ 			       so the number of locks is:
+ 			       ((-lock_word) / X_LOCK_DECR) + 1
+When lock_word <= -X_LOCK_DECR, we also know that lock_word % X_LOCK_DECR == 0:
+other values of lock_word are invalid.
+ 
+The lock_word is always read and updated atomically and consistently, so that
+it always represents the state of the lock, and the state of the lock changes
+with a single atomic operation. This lock_word holds all of the information
+that a thread needs in order to determine if it is eligible to gain the lock
+or if it must spin or sleep. The one exception to this is that writer_thread
+must be verified before recursive write locks: to solve this scenario, we make
+writer_thread readable by all threads, but only writeable by the x-lock holder.
+
+The other members of the lock obey the following rules to remain consistent:
+ 
+pass:		This is only set to 1 to prevent recursive x-locks. It must
+ 		be set as specified by x_lock caller after the lock_word
+ 		indicates that the thread holds the lock, but before that
+ 		thread resumes execution. It must be reset to 0 during the
+ 		final x_unlock, but before the lock_word status is updated.
+ 		When an x_lock or move_ownership call wishes to change
+ 		pass, it must first update the writer_thread appropriately.
+writer_thread:	Must be set to the writers thread_id after the lock_word
+ 		indicates that the thread holds the lock, but before that
+ 		thread resumes execution. It  must be reset to -1 during the
+ 		final x_unlock, but before the lock_word status is updated.
+ 		This ensures that when the lock_word indicates that an x_lock
+ 		is held, the only legitimate values for writer_thread are -1
+ 		(x_lock function hasn't completed) or the writer's thread_id.
+waiters:	May be set to 1 anytime, but to avoid unnecessary wake-up
+ 		signals, it should only be set to 1 when there are threads
+ 		waiting on event. Must be 1 when a writer starts waiting to
+ 		ensure the current x-locking thread sends a wake-up signal
+ 		during unlock. May only be reset to 0 immediately before a
+ 		a wake-up signal is sent to event.
+event:		Threads wait on event for read or writer lock when another
+ 		thread has an x-lock or an x-lock reservation (wait_ex). A
+ 		thread may only	wait on event after performing the following
+ 		actions in order:
+ 		   (1) Record the counter value of event (with os_event_reset).
+ 		   (2) Set waiters to 1.
+ 		   (3) Verify lock_word <= 0.
+ 		(1) must come before (2) to ensure signal is not missed.
+ 		(2) must come before (3) to ensure a signal is sent.
+ 		These restrictions force the above ordering.
+ 		Immediately before sending the wake-up signal, we should:
+ 		   (1) Verify lock_word == X_LOCK_DECR (unlocked)
+ 		   (2) Reset waiters to 0.
+wait_ex_event:	A thread may only wait on the wait_ex_event after it has
+ 		performed the following actions in order:
+ 		   (1) Decrement lock_word by X_LOCK_DECR.
+ 		   (2) Record counter value of wait_ex_event (os_event_reset,
+                        called from sync_array_reserve_cell).
+ 		   (3) Verify that lock_word < 0.
+ 		(1) must come first to ensures no other threads become reader
+                 or next writer, and notifies unlocker that signal must be sent.
+                 (2) must come before (3) to ensure the signal is not missed.
+ 		These restrictions force the above ordering.
+ 		Immediately before sending the wake-up signal, we should:
+		   Verify lock_word == 0 (waiting thread holds x_lock)
+*/
+
 
 /* number of spin waits on rw-latches,
 resulted during shared (read) locks */
-ulint	rw_s_spin_wait_count	= 0;
+ib_longlong	rw_s_spin_wait_count	= 0;
+ib_longlong	rw_s_spin_round_count	= 0;
 
 /* number of OS waits on rw-latches,
 resulted during shared (read) locks */
-ulint	rw_s_os_wait_count	= 0;
+ib_longlong	rw_s_os_wait_count	= 0;
 
 /* number of unlocks (that unlock shared locks),
 set only when UNIV_SYNC_PERF_STAT is defined */
-ulint	rw_s_exit_count		= 0;
+ib_longlong	rw_s_exit_count		= 0;
-
-/* number of system calls made during exclusive latching */
-ulint	rw_x_system_call_count	= 0;
 
 /* number of spin waits on rw-latches,
 resulted during exclusive (write) locks */
-ulint	rw_x_spin_wait_count	= 0;
+ib_longlong	rw_x_spin_wait_count	= 0;
+ib_longlong	rw_x_spin_round_count	= 0;
 
 /* number of OS waits on rw-latches,
 resulted during exclusive (write) locks */
-ulint	rw_x_os_wait_count	= 0;
+ib_longlong	rw_x_os_wait_count	= 0;
 
 /* number of unlocks (that unlock exclusive locks),
 set only when UNIV_SYNC_PERF_STAT is defined */
-ulint	rw_x_exit_count		= 0;
+ib_longlong	rw_x_exit_count		= 0;
 
 /* The global list of rw-locks */
 rw_lock_list_t	rw_lock_list;
@@ -119,6 +195,7 @@ 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;
@@ -129,12 +206,12 @@ rw_lock_create_func(
 	lock->mutex.mutex_type = 1;
 #endif /* UNIV_DEBUG && !UNIV_HOTBACKUP */
 
-	rw_lock_set_waiters(lock, 0);
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
-	rw_lock_set_writer(lock, RW_LOCK_NOT_LOCKED);
-	lock->writer_count = 0;
-	rw_lock_set_reader_count(lock, 0);
 
-	lock->writer_is_wait_ex = FALSE;
+	lock->lock_word = X_LOCK_DECR;
+	rw_lock_set_waiters(lock, 0);
+	lock->writer_thread = -1;
+	lock->pass = 0;
 
 #ifdef UNIV_SYNC_DEBUG
 	UT_LIST_INIT(lock->debug_list);
@@ -147,15 +224,13 @@ rw_lock_create_func(
 	lock->cfile_name = cfile_name;
 	lock->cline = (unsigned int) cline;
 
+	lock->count_os_wait = 0;
 	lock->last_s_file_name = "not yet reserved";
 	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->wait_ex_event = os_event_create(NULL);
-#endif
 
 	mutex_enter(&rw_lock_list_mutex);
 
@@ -180,20 +255,19 @@ rw_lock_free(
 	rw_lock_t*	lock)	/* in: rw-lock */
 {
 	ut_ad(rw_lock_validate(lock));
-	ut_a(rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED);
+	ut_a(lock->lock_word == X_LOCK_DECR);
 	ut_a(rw_lock_get_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 /* HAVE_GCC_ATOMIC_BUILTINS */
 
 	mutex_enter(&rw_lock_list_mutex);
 	os_event_free(lock->event);
 
-#ifdef __WIN__
 	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);
@@ -219,19 +293,12 @@ rw_lock_validate(
 {
 	ut_a(lock);
 
-	mutex_enter(rw_lock_get_mutex(lock));
+	ulint waiters = rw_lock_get_waiters(lock);
+	lint lock_word = lock->lock_word;
 
 	ut_a(lock->magic_n == RW_LOCK_MAGIC_N);
-	ut_a((rw_lock_get_reader_count(lock) == 0)
+	ut_a(waiters == 0 || waiters == 1);
-	     || (rw_lock_get_writer(lock) != RW_LOCK_EX));
+	ut_a(lock_word > -X_LOCK_DECR ||(-lock_word) % X_LOCK_DECR == 0);
-	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((lock->writer != RW_LOCK_EX) || (lock->writer_count > 0));
-
-	mutex_exit(rw_lock_get_mutex(lock));
 
 	return(TRUE);
 }
@@ -253,18 +320,15 @@ rw_lock_s_lock_spin(
 	ulint		line)	/* in: line where requested */
 {
 	ulint	 index;	/* index of the reserved wait cell */
-	ulint	 i;	/* spin round count */
+	ulint	 i = 0;	/* spin round count */
 
 	ut_ad(rw_lock_validate(lock));
 
+	rw_s_spin_wait_count++;	/* Count calls to this function */
 lock_loop:
-	rw_s_spin_wait_count++;
 
 	/* Spin waiting for the writer field to become free */
-	i = 0;
+	while (i < SYNC_SPIN_ROUNDS && lock->lock_word <= 0) {
-
-	while (rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED
-	       && i < SYNC_SPIN_ROUNDS) {
 		if (srv_spin_wait_delay) {
 			ut_delay(ut_rnd_interval(0, srv_spin_wait_delay));
 		}
@@ -285,28 +349,32 @@ lock_loop:
 			lock->cfile_name, (ulong) lock->cline, (ulong) i);
 	}
 
-	mutex_enter(rw_lock_get_mutex(lock));
-
 	/* We try once again to obtain the lock */
-
 	if (TRUE == rw_lock_s_lock_low(lock, pass, file_name, line)) {
-		mutex_exit(rw_lock_get_mutex(lock));
+		rw_s_spin_round_count += i;
 
 		return; /* Success */
 	} else {
-		/* If we get here, locking did not succeed, we may
-		suspend the thread to wait in the wait array */
 
-		rw_s_system_call_count++;
+		if (i < SYNC_SPIN_ROUNDS) {
+			goto lock_loop;
+		}
+
+		rw_s_spin_round_count += i;
 
 		sync_array_reserve_cell(sync_primary_wait_array,
 					lock, RW_LOCK_SHARED,
 					file_name, line,
 					&index);
 
+		/* Set waiters before checking lock_word to ensure wake-up
+                signal is sent. This may lead to some unnecessary signals. */
 		rw_lock_set_waiters(lock, 1);
 
-		mutex_exit(rw_lock_get_mutex(lock));
+		if (TRUE == rw_lock_s_lock_low(lock, pass, file_name, line)) {
+			sync_array_free_cell(sync_primary_wait_array, index);
+			return; /* Success */
+		}
 
 		if (srv_print_latch_waits) {
 			fprintf(stderr,
@@ -317,11 +385,13 @@ lock_loop:
 				(ulong) lock->cline);
 		}
 
-		rw_s_system_call_count++;
+		/* these stats may not be accurate */
+		lock->count_os_wait++;
 		rw_s_os_wait_count++;
 
 		sync_array_wait_event(sync_primary_wait_array, index);
 
+		i = 0;
 		goto lock_loop;
 	}
 }
@@ -343,113 +413,149 @@ rw_lock_x_lock_move_ownership(
 {
 	ut_ad(rw_lock_is_locked(lock, RW_LOCK_EX));
 
-	mutex_enter(&(lock->mutex));
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
-
+        os_thread_id_t local_writer_thread = lock->writer_thread;
-	lock->writer_thread = os_thread_get_curr_id();
+        os_thread_id_t new_writer_thread = os_thread_get_curr_id();
-
+        while (TRUE) {
+                if (local_writer_thread != -1) {
+                        if(os_compare_and_swap(
+                               &(lock->writer_thread),
+                               local_writer_thread,
+                               new_writer_thread)) {
+                                break;
+                        }
+                }
+                local_writer_thread = lock->writer_thread;
+        }
+	lock->pass = 0;
+#else /* HAVE_GCC_ATOMIC_BUILTINS */
+	mutex_enter(&(lock->mutex));
+	lock->writer_thread = os_thread_get_curr_id();
 	lock->pass = 0;
-
 	mutex_exit(&(lock->mutex));
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
+}
+
+/**********************************************************************
+Function for the next writer to call. Waits for readers to exit.
+The caller must have already decremented lock_word by X_LOCK_DECR.*/
+UNIV_INLINE
+void
+rw_lock_x_lock_wait(
+/*================*/
+	rw_lock_t*	lock,	/* in: pointer to rw-lock */
+#ifdef UNIV_SYNC_DEBUG
+	ulint		pass,	/* in: pass value; != 0, if the lock will
+				be passed to another thread to unlock */
+#endif
+	const char*	file_name,/* in: file name where lock requested */
+	ulint		line)	/* in: line where requested */
+{
+	ulint index;
+	ulint i = 0;
+
+	ut_ad(lock->lock_word <= 0);
+
+	while (lock->lock_word < 0) {
+		if (srv_spin_wait_delay) {
+			ut_delay(ut_rnd_interval(0, srv_spin_wait_delay));
+		}
+		if(i < SYNC_SPIN_ROUNDS) {
+			i++;
+			continue;
+		}
+
+		/* If there is still a reader, then go to sleep.*/
+		rw_x_spin_round_count += i;
+		i = 0;
+		sync_array_reserve_cell(sync_primary_wait_array,
+					lock,
+					RW_LOCK_WAIT_EX,
+					file_name, line,
+					&index);
+		/* Check lock_word to ensure wake-up isn't missed.*/
+		if(lock->lock_word < 0) {
+
+			/* these stats may not be accurate */
+			lock->count_os_wait++;
+			rw_x_os_wait_count++;
+
+                        /* Add debug info as it is needed to detect possible
+                        deadlock. We must add info for WAIT_EX thread for
+                        deadlock detection to work properly. */
+#ifdef UNIV_SYNC_DEBUG
+			rw_lock_add_debug_info(lock, pass, RW_LOCK_WAIT_EX,
+					       file_name, line);
+#endif
+
+ 			sync_array_wait_event(sync_primary_wait_array,
+ 					      index);
+#ifdef UNIV_SYNC_DEBUG
+			rw_lock_remove_debug_info(lock, pass,
+					       RW_LOCK_WAIT_EX);
+#endif
+                        /* It is possible to wake when lock_word < 0.
+                        We must pass the while-loop check to proceed.*/
+		} else {
+			sync_array_free_cell(sync_primary_wait_array,
+					     index);
+		}
+	}
+	rw_x_spin_round_count += i;
 }
 
 /**********************************************************************
 Low-level function for acquiring an exclusive lock. */
 UNIV_INLINE
-ulint
+ibool
 rw_lock_x_lock_low(
 /*===============*/
 				/* out: RW_LOCK_NOT_LOCKED if did
-				not succeed, RW_LOCK_EX if success,
+				not succeed, RW_LOCK_EX if success. */
-				RW_LOCK_WAIT_EX, if got wait reservation */
 	rw_lock_t*	lock,	/* in: pointer to rw-lock */
 	ulint		pass,	/* in: pass value; != 0, if the lock will
 				be passed to another thread to unlock */
 	const char*	file_name,/* in: file name where lock requested */
 	ulint		line)	/* in: line where requested */
 {
-	ut_ad(mutex_own(rw_lock_get_mutex(lock)));
+	os_thread_id_t	curr_thread	= os_thread_get_curr_id();
+	ut_ad(curr_thread != -1); /* We use -1 as the unlocked value. */
 
-	if (rw_lock_get_writer(lock) == RW_LOCK_NOT_LOCKED) {
+	if(rw_lock_lock_word_decr(lock, X_LOCK_DECR)) {
-
+		ut_ad(lock->writer_thread == -1);
-		if (rw_lock_get_reader_count(lock) == 0) {
-
-			rw_lock_set_writer(lock, RW_LOCK_EX);
-			lock->writer_thread = os_thread_get_curr_id();
-			lock->writer_count++;
-			lock->pass = pass;
 
+		/* Decrement occurred: we are writer or next-writer. */
+		lock->writer_thread = curr_thread;
+		lock->pass = pass;
+		rw_lock_x_lock_wait(lock,
 #ifdef UNIV_SYNC_DEBUG
-			rw_lock_add_debug_info(lock, pass, RW_LOCK_EX,
+				    pass,
-					       file_name, line);
 #endif
-			lock->last_x_file_name = file_name;
+                                    file_name, line);
-			lock->last_x_line = (unsigned int) line;
 
-			/* Locking succeeded, we may return */
+	} else {
-			return(RW_LOCK_EX);
+		/* Decrement failed: relock or failed lock */
+		/* Must verify pass first: otherwise another thread can
+		call move_ownership suddenly allowing recursive locks.
+		and after we have verified our thread_id matches
+		(though move_ownership has since changed it).*/
+		if(!pass && !(lock->pass) &&
+                   os_thread_eq(lock->writer_thread, curr_thread)) {
+			/* Relock */
+                        lock->lock_word -= X_LOCK_DECR;
 		} else {
-			/* There are readers, we have to wait */
+			/* Another thread locked before us */
-			rw_lock_set_writer(lock, RW_LOCK_WAIT_EX);
+			return(FALSE);
-			lock->writer_thread = os_thread_get_curr_id();
-			lock->pass = pass;
-			lock->writer_is_wait_ex = TRUE;
-
-#ifdef UNIV_SYNC_DEBUG
-			rw_lock_add_debug_info(lock, pass, RW_LOCK_WAIT_EX,
-					       file_name, line);
-#endif
-
-			return(RW_LOCK_WAIT_EX);
 		}
-
-	} else if ((rw_lock_get_writer(lock) == RW_LOCK_WAIT_EX)
-		   && os_thread_eq(lock->writer_thread,
-				   os_thread_get_curr_id())) {
-
-		if (rw_lock_get_reader_count(lock) == 0) {
-
-			rw_lock_set_writer(lock, RW_LOCK_EX);
-			lock->writer_count++;
-			lock->pass = pass;
-			lock->writer_is_wait_ex = FALSE;
-
-#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 = (unsigned int) line;
-
-			/* Locking succeeded, we may return */
-			return(RW_LOCK_EX);
-		}
-
-		return(RW_LOCK_WAIT_EX);
-
-	} else if ((rw_lock_get_writer(lock) == RW_LOCK_EX)
-		   && os_thread_eq(lock->writer_thread,
-				   os_thread_get_curr_id())
-		   && (lock->pass == 0)
-		   && (pass == 0)) {
-
-		lock->writer_count++;
-
-#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 = (unsigned int) line;
-
-		/* Locking succeeded, we may return */
-		return(RW_LOCK_EX);
 	}
+#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 = (unsigned int) line;
 
-	/* Locking did not succeed */
+	return(TRUE);
-	return(RW_LOCK_NOT_LOCKED);
 }
 
 /**********************************************************************
@@ -472,62 +578,46 @@ 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	i;	/* spin round count */
+	ibool   spinning = FALSE;
 
 	ut_ad(rw_lock_validate(lock));
 
+	i = 0;
+
 lock_loop:
-	/* Acquire the mutex protecting the rw-lock fields */
-	mutex_enter_fast(&(lock->mutex));
 
-	state = rw_lock_x_lock_low(lock, pass, file_name, line);
+	if (rw_lock_x_lock_low(lock, pass, file_name, line)) {
-
+		rw_x_spin_round_count += i;
-	mutex_exit(&(lock->mutex));
-
-	if (state == RW_LOCK_EX) {
 
 		return;	/* Locking succeeded */
 
-	} 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) {
-			if (srv_spin_wait_delay) {
-				ut_delay(ut_rnd_interval(0,
-							 srv_spin_wait_delay));
-			}
-
-			i++;
-		}
-		if (i == SYNC_SPIN_ROUNDS) {
-			os_thread_yield();
-		}
-	} else if (state == RW_LOCK_WAIT_EX) {
-
-		/* Spin waiting for the reader count field to become zero */
-		i = 0;
-
-		while (rw_lock_get_reader_count(lock) != 0
-		       && i < SYNC_SPIN_ROUNDS) {
-			if (srv_spin_wait_delay) {
-				ut_delay(ut_rnd_interval(0,
-							 srv_spin_wait_delay));
-			}
-
-			i++;
-		}
-		if (i == SYNC_SPIN_ROUNDS) {
-			os_thread_yield();
-		}
 	} else {
-		i = 0; /* Eliminate a compiler warning */
+
-		ut_error;
+                if (!spinning) {
+                        spinning = TRUE;
+                        rw_x_spin_wait_count++;
+		}
+
+		/* Spin waiting for the lock_word to become free */
+		while (i < SYNC_SPIN_ROUNDS
+		       && lock->lock_word <= 0) {
+			if (srv_spin_wait_delay) {
+				ut_delay(ut_rnd_interval(0,
+							 srv_spin_wait_delay));
+			}
+
+			i++;
+		}
+		if (i == SYNC_SPIN_ROUNDS) {
+			os_thread_yield();
+		} else {
+			goto lock_loop;
+		}
 	}
 
+	rw_x_spin_round_count += i;
+
 	if (srv_print_latch_waits) {
 		fprintf(stderr,
 			"Thread %lu spin wait rw-x-lock at %p"
@@ -536,39 +626,20 @@ lock_loop:
 			lock->cfile_name, (ulong) lock->cline, (ulong) i);
 	}
 
-	rw_x_spin_wait_count++;
-
-	/* We try once again to obtain the lock. Acquire the mutex protecting
-	the rw-lock fields */
-
-	mutex_enter(rw_lock_get_mutex(lock));
-
-	state = rw_lock_x_lock_low(lock, pass, file_name, line);
-
-	if (state == RW_LOCK_EX) {
-		mutex_exit(rw_lock_get_mutex(lock));
-
-		return;	/* Locking succeeded */
-	}
-
-	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);
 
+	/* Waiters must be set before checking lock_word, to ensure signal
+	is sent. This could lead to a few unnecessary wake-up signals. */
 	rw_lock_set_waiters(lock, 1);
 
-	mutex_exit(rw_lock_get_mutex(lock));
+	if (rw_lock_x_lock_low(lock, pass, file_name, line)) {
+		sync_array_free_cell(sync_primary_wait_array, index);
+		return; /* Locking succeeded */
+	}
 
 	if (srv_print_latch_waits) {
 		fprintf(stderr,
@@ -578,11 +649,13 @@ lock_loop:
 			lock->cfile_name, (ulong) lock->cline);
 	}
 
-	rw_x_system_call_count++;
+	/* these stats may not be accurate */
+	lock->count_os_wait++;
 	rw_x_os_wait_count++;
 
 	sync_array_wait_event(sync_primary_wait_array, index);
 
+	i = 0;
 	goto lock_loop;
 }
 
@@ -730,7 +803,7 @@ rw_lock_own(
 	ut_ad(lock);
 	ut_ad(rw_lock_validate(lock));
 
-	mutex_enter(&(lock->mutex));
+	rw_lock_debug_mutex_enter();
 
 	info = UT_LIST_GET_FIRST(lock->debug_list);
 
@@ -740,7 +813,7 @@ rw_lock_own(
 		    && (info->pass == 0)
 		    && (info->lock_type == lock_type)) {
 
-			mutex_exit(&(lock->mutex));
+			rw_lock_debug_mutex_exit();
 			/* Found! */
 
 			return(TRUE);
@@ -748,7 +821,7 @@ rw_lock_own(
 
 		info = UT_LIST_GET_NEXT(list, info);
 	}
-	mutex_exit(&(lock->mutex));
+	rw_lock_debug_mutex_exit();
 
 	return(FALSE);
 }
@@ -770,22 +843,18 @@ rw_lock_is_locked(
 	ut_ad(lock);
 	ut_ad(rw_lock_validate(lock));
 
-	mutex_enter(&(lock->mutex));
-
 	if (lock_type == RW_LOCK_SHARED) {
-		if (lock->reader_count > 0) {
+		if (rw_lock_get_reader_count(lock) > 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;
 	}
 
-	mutex_exit(&(lock->mutex));
-
 	return(ret);
 }
 
@@ -814,11 +883,10 @@ 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)
+		if (lock->lock_word != X_LOCK_DECR) {
-		    || (rw_lock_get_reader_count(lock) != 0)
-		    || (rw_lock_get_waiters(lock) != 0)) {
 
 			fprintf(file, "RW-LOCK: %p ", (void*) lock);
 
@@ -834,8 +902,10 @@ rw_lock_list_print_info(
 				info = UT_LIST_GET_NEXT(list, info);
 			}
 		}
-
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
 		mutex_exit(&(lock->mutex));
+#endif
+
 		lock = UT_LIST_GET_NEXT(list, lock);
 	}
 
@@ -858,9 +928,10 @@ rw_lock_print(
 		"RW-LATCH INFO\n"
 		"RW-LATCH: %p ", (void*) lock);
 
-	if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
-	    || (rw_lock_get_reader_count(lock) != 0)
+	mutex_enter(&(lock->mutex));
-	    || (rw_lock_get_waiters(lock) != 0)) {
+#endif
+	if (lock->lock_word != X_LOCK_DECR) {
 
 		if (rw_lock_get_waiters(lock)) {
 			fputs(" Waiters for the lock exist\n", stderr);
@@ -874,6 +945,9 @@ rw_lock_print(
 			info = UT_LIST_GET_NEXT(list, info);
 		}
 	}
+#ifndef HAVE_GCC_ATOMIC_BUILTINS
+	mutex_exit(&(lock->mutex));
+#endif
 }
 
 /*************************************************************************
@@ -922,14 +996,11 @@ rw_lock_n_locked(void)
 	lock = UT_LIST_GET_FIRST(rw_lock_list);
 
 	while (lock != NULL) {
-		mutex_enter(rw_lock_get_mutex(lock));
 
-		if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
+		if (lock->lock_word != X_LOCK_DECR) {
-		    || (rw_lock_get_reader_count(lock) != 0)) {
 			count++;
 		}
 
-		mutex_exit(rw_lock_get_mutex(lock));
 		lock = UT_LIST_GET_NEXT(list, lock);
 	}
 

storage/innobase/sync/sync0sync.c

@@ -138,18 +138,13 @@ Therefore, this thread is guaranteed to catch the os_set_event()
 signalled unconditionally at the release of the lock.
 Q.E.D. */
 
-/* The number of system calls made in this module. Intended for performance
-monitoring. */
-
-ulint	mutex_system_call_count		= 0;
-
 /* Number of spin waits on mutexes: for performance monitoring */
 
 /* round=one iteration of a spin loop */
-ulint	mutex_spin_round_count		= 0;
+ib_longlong	mutex_spin_round_count		= 0;
-ulint	mutex_spin_wait_count		= 0;
+ib_longlong	mutex_spin_wait_count		= 0;
-ulint	mutex_os_wait_count		= 0;
+ib_longlong	mutex_os_wait_count		= 0;
-ulint	mutex_exit_count		= 0;
+ib_longlong	mutex_exit_count		= 0;
 
 /* The global array of wait cells for implementation of the database's own
 mutexes and read-write locks */
@@ -243,6 +238,8 @@ mutex_create_func(
 {
 #if defined(_WIN32) && defined(UNIV_CAN_USE_X86_ASSEMBLER)
 	mutex_reset_lock_word(mutex);
+#elif defined(HAVE_GCC_ATOMIC_BUILTINS)
+	mutex_reset_lock_word(mutex);
 #else
 	os_fast_mutex_init(&(mutex->os_fast_mutex));
 	mutex->lock_word = 0;
@@ -333,7 +330,9 @@ mutex_free(
 
 	os_event_free(mutex->event);
 
-#if !defined(_WIN32) || !defined(UNIV_CAN_USE_X86_ASSEMBLER)
+#if defined(_WIN32) && defined(UNIV_CAN_USE_X86_ASSEMBLER)
+#elif defined(HAVE_GCC_ATOMIC_BUILTINS)
+#else
 	os_fast_mutex_free(&(mutex->os_fast_mutex));
 #endif
 	/* If we free the mutex protecting the mutex list (freeing is
@@ -450,6 +449,12 @@ mutex_spin_wait(
 #endif /* UNIV_DEBUG && !UNIV_HOTBACKUP */
 	ut_ad(mutex);
 
+	/* This update is not thread safe, but we don't mind if the count
+	isn't exact. Moved out of ifdef that follows because we are willing
+	to sacrifice the cost of counting this as the data is valuable.
+	Count the number of calls to mutex_spin_wait. */
+	mutex_spin_wait_count++;
+
 mutex_loop:
 
 	i = 0;
@@ -462,7 +467,6 @@ mutex_loop:
 
 spin_loop:
 #if defined UNIV_DEBUG && !defined UNIV_HOTBACKUP
-	mutex_spin_wait_count++;
 	mutex->count_spin_loop++;
 #endif /* UNIV_DEBUG && !UNIV_HOTBACKUP */
 
@@ -527,8 +531,6 @@ spin_loop:
 	sync_array_reserve_cell(sync_primary_wait_array, mutex,
 				SYNC_MUTEX, file_name, line, &index);
 
-	mutex_system_call_count++;
-
 	/* The memory order of the array reservation and the change in the
 	waiters field is important: when we suspend a thread, we first
 	reserve the cell and then set waiters field to 1. When threads are
@@ -575,7 +577,6 @@ spin_loop:
 		mutex->cfile_name, (ulong) mutex->cline, (ulong) i);
 #endif
 
-	mutex_system_call_count++;
 	mutex_os_wait_count++;
 
 #ifndef UNIV_HOTBACKUP
@@ -1377,21 +1378,31 @@ sync_print_wait_info(
 	FILE*	file)		/* in: file where to print */
 {
 #ifdef UNIV_SYNC_DEBUG
-	fprintf(file, "Mutex exits %lu, rws exits %lu, rwx exits %lu\n",
+	fprintf(file, "Mutex exits %llu, rws exits %llu, rwx exits %llu\n",
 		mutex_exit_count, rw_s_exit_count, rw_x_exit_count);
 #endif
 
 	fprintf(file,
-		"Mutex spin waits %lu, rounds %lu, OS waits %lu\n"
+		"Mutex spin waits %llu, rounds %llu, OS waits %llu\n"
-		"RW-shared spins %lu, OS waits %lu;"
+		"RW-shared spins %llu, OS waits %llu;"
-		" RW-excl spins %lu, OS waits %lu\n",
+		" RW-excl spins %llu, OS waits %llu\n",
-		(ulong) mutex_spin_wait_count,
+		mutex_spin_wait_count,
-		(ulong) mutex_spin_round_count,
+		mutex_spin_round_count,
-		(ulong) mutex_os_wait_count,
+		mutex_os_wait_count,
-		(ulong) rw_s_spin_wait_count,
+		rw_s_spin_wait_count,
-		(ulong) rw_s_os_wait_count,
+		rw_s_os_wait_count,
-		(ulong) rw_x_spin_wait_count,
+		rw_x_spin_wait_count,
-		(ulong) rw_x_os_wait_count);
+		rw_x_os_wait_count);
+
+	fprintf(file,
+		"Spin rounds per wait: %.2f mutex, %.2f RW-shared, "
+		"%.2f RW-excl\n",
+		(double) mutex_spin_round_count /
+		(mutex_spin_wait_count ? mutex_spin_wait_count : 1),
+		(double) rw_s_spin_round_count /
+		(rw_s_spin_wait_count ? rw_s_spin_wait_count : 1),
+		(double) rw_x_spin_round_count /
+		(rw_x_spin_wait_count ? rw_x_spin_wait_count : 1));
 }
 
 /***********************************************************************