sync0rw.c

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	} 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 (srv_print_latch_waits) {
		fprintf(stderr,
	"Thread %lu spin wait rw-x-lock at %p cfile %s cline %lu rnds %lu\n",
			os_thread_pf(os_thread_get_curr_id()), lock,
		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, RW_LOCK_EX,
				file_name, line,
				&index);

	rw_lock_set_waiters(lock, 1);

	mutex_exit(rw_lock_get_mutex(lock));

	if (srv_print_latch_waits) {
		fprintf(stderr,
		"Thread %lu OS wait for rw-x-lock at %p cfile %s cline %lu\n",
			os_thread_pf(os_thread_get_curr_id()), lock,
		lock->cfile_name, (ulong) lock->cline);
	}

	rw_x_system_call_count++;
	rw_x_os_wait_count++;

        sync_array_wait_event(sync_primary_wait_array, index);

        goto lock_loop;
}

#ifdef UNIV_SYNC_DEBUG
/**********************************************************************
Acquires the debug mutex. We cannot use the mutex defined in sync0sync,
because the debug mutex is also acquired in sync0arr while holding the OS
mutex protecting the sync array, and the ordinary mutex_enter might
recursively call routines in sync0arr, leading to a deadlock on the OS
mutex. */

void
rw_lock_debug_mutex_enter(void)
/*==========================*/
{
loop:
	if (0 == mutex_enter_nowait(&rw_lock_debug_mutex,
			__FILE__, __LINE__)) {
		return;
	}

	os_event_reset(rw_lock_debug_event);

	rw_lock_debug_waiters = TRUE;

	if (0 == mutex_enter_nowait(&rw_lock_debug_mutex,
			__FILE__, __LINE__)) {
		return;
	}

	os_event_wait(rw_lock_debug_event);

	goto loop;	
}

/**********************************************************************
Releases the debug mutex. */

void
rw_lock_debug_mutex_exit(void)
/*==========================*/
{
	mutex_exit(&rw_lock_debug_mutex);

	if (rw_lock_debug_waiters) {
		rw_lock_debug_waiters = FALSE;
		os_event_set(rw_lock_debug_event);
	}
}

/**********************************************************************
Inserts the debug information for an rw-lock. */

void
rw_lock_add_debug_info(
/*===================*/
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		pass,		/* in: pass value */
	ulint		lock_type,	/* in: lock type */
	const char*	file_name,	/* in: file where requested */
	ulint		line)		/* in: line where requested */
{
	rw_lock_debug_t*	info;

	ut_ad(lock);
	ut_ad(file_name);

	info = rw_lock_debug_create();

	rw_lock_debug_mutex_enter();

	info->file_name = file_name;
	info->line 	= line;
	info->lock_type = lock_type;
	info->thread_id = os_thread_get_curr_id();
	info->pass	= pass;

	UT_LIST_ADD_FIRST(list, lock->debug_list, info);	

	rw_lock_debug_mutex_exit();

	if ((pass == 0) && (lock_type != RW_LOCK_WAIT_EX)) {
		sync_thread_add_level(lock, lock->level);
	}
}	

/**********************************************************************
Removes a debug information struct for an rw-lock. */

void
rw_lock_remove_debug_info(
/*======================*/
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		pass,		/* in: pass value */
	ulint		lock_type)	/* in: lock type */
{
	rw_lock_debug_t*	info;

	ut_ad(lock);

	if ((pass == 0) && (lock_type != RW_LOCK_WAIT_EX)) {
		sync_thread_reset_level(lock);
	}

	rw_lock_debug_mutex_enter();

	info = UT_LIST_GET_FIRST(lock->debug_list);

	while (info != NULL) {
		if ((pass == info->pass)
		    && ((pass != 0)
			|| os_thread_eq(info->thread_id,
						os_thread_get_curr_id()))
		    && (info->lock_type == lock_type)) {

		    	/* Found! */
		    	UT_LIST_REMOVE(list, lock->debug_list, info);
			rw_lock_debug_mutex_exit();

		    	rw_lock_debug_free(info);

		    	return;
		}

		info = UT_LIST_GET_NEXT(list, info);
	}

	ut_error;
}
#endif /* UNIV_SYNC_DEBUG */

/**********************************************************************
Sets the rw-lock latching level field. */

void
rw_lock_set_level(
/*==============*/
	rw_lock_t*	lock,	/* in: rw-lock */
	ulint		level)	/* in: level */
{
	lock->level = level;
}

#ifdef UNIV_SYNC_DEBUG
/**********************************************************************
Checks if the thread has locked the rw-lock in the specified mode, with
the pass value == 0. */

ibool
rw_lock_own(
/*========*/
					/* out: TRUE if locked */
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		lock_type)	/* in: lock type: RW_LOCK_SHARED,
					RW_LOCK_EX */
{
	rw_lock_debug_t*	info;

	ut_ad(lock);
	ut_ad(rw_lock_validate(lock));

	mutex_enter(&(lock->mutex));

	info = UT_LIST_GET_FIRST(lock->debug_list);

	while (info != NULL) {

		if (os_thread_eq(info->thread_id, os_thread_get_curr_id())
		    && (info->pass == 0)
		    && (info->lock_type == lock_type)) {

			mutex_exit(&(lock->mutex));
		    	/* Found! */

		    	return(TRUE);
		}

		info = UT_LIST_GET_NEXT(list, info);
	}
	mutex_exit(&(lock->mutex));

	return(FALSE);
}
#endif /* UNIV_SYNC_DEBUG */

/**********************************************************************
Checks if somebody has locked the rw-lock in the specified mode. */

ibool
rw_lock_is_locked(
/*==============*/
					/* out: TRUE if locked */
	rw_lock_t*	lock,		/* in: rw-lock */
	ulint		lock_type)	/* in: lock type: RW_LOCK_SHARED,
					RW_LOCK_EX */
{
	ibool	ret	= FALSE;

	ut_ad(lock);
	ut_ad(rw_lock_validate(lock));
	
	mutex_enter(&(lock->mutex));

	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) {
			ret = TRUE;
		}
	} else {
		ut_error;
	}

	mutex_exit(&(lock->mutex));

	return(ret);
}

#ifdef UNIV_SYNC_DEBUG
/*******************************************************************
Prints debug info of currently locked rw-locks. */

void
rw_lock_list_print_info(void)
/*=========================*/
{
	rw_lock_t*	lock;
	ulint		count		= 0;
	rw_lock_debug_t* info;
	
	mutex_enter(&rw_lock_list_mutex);

	fputs("-------------\n"
		"RW-LATCH INFO\n"
		"-------------\n", stderr);

	lock = UT_LIST_GET_FIRST(rw_lock_list);

	while (lock != NULL) {

		count++;

		mutex_enter(&(lock->mutex));

		if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
		    || (rw_lock_get_reader_count(lock) != 0)
		    || (rw_lock_get_waiters(lock) != 0)) {

			fprintf(stderr, "RW-LOCK: %p ", lock);

			if (rw_lock_get_waiters(lock)) {
				fputs(" Waiters for the lock exist\n", stderr);
			} else {
				putc('\n', stderr);
			}
		    
			info = UT_LIST_GET_FIRST(lock->debug_list);
			while (info != NULL) {	
				rw_lock_debug_print(info);
				info = UT_LIST_GET_NEXT(list, info);
			}
		}

		mutex_exit(&(lock->mutex));
		lock = UT_LIST_GET_NEXT(list, lock);
	}

	fprintf(stderr, "Total number of rw-locks %ld\n", count);
	mutex_exit(&rw_lock_list_mutex);
}

/*******************************************************************
Prints debug info of an rw-lock. */

void
rw_lock_print(
/*==========*/
	rw_lock_t*	lock)	/* in: rw-lock */
{
	rw_lock_debug_t* info;
	
	fprintf(stderr,
		"-------------\n"
		"RW-LATCH INFO\n"
		"RW-LATCH: %p ", lock);

	if ((rw_lock_get_writer(lock) != RW_LOCK_NOT_LOCKED)
	    || (rw_lock_get_reader_count(lock) != 0)
	    || (rw_lock_get_waiters(lock) != 0)) {

		if (rw_lock_get_waiters(lock)) {
			fputs(" Waiters for the lock exist\n", stderr);
		} else {
			putc('\n', stderr);
		}
		    
		info = UT_LIST_GET_FIRST(lock->debug_list);
		while (info != NULL) {	
			rw_lock_debug_print(info);
			info = UT_LIST_GET_NEXT(list, info);
		}
	}
}

/*************************************************************************
Prints info of a debug struct. */

void
rw_lock_debug_print(
/*================*/
	rw_lock_debug_t*	info)	/* in: debug struct */
{
	ulint	rwt;

	rwt 	  = info->lock_type;	
			
	fprintf(stderr, "Locked: thread %ld file %s line %ld  ",
		(ulong) os_thread_pf(info->thread_id), info->file_name,
	        (ulong) info->line);
	if (rwt == RW_LOCK_SHARED) {
		fputs("S-LOCK", stderr);
	} else if (rwt == RW_LOCK_EX) {
		fputs("X-LOCK", stderr);
	} else if (rwt == RW_LOCK_WAIT_EX) {
		fputs("WAIT X-LOCK", stderr);
	} else {
		ut_error;
	}
	if (info->pass != 0) {
		fprintf(stderr, " pass value %lu", (ulong) info->pass);
	}
	putc('\n', stderr);
}

/*******************************************************************
Returns the number of currently locked rw-locks. Works only in the debug
version. */

ulint
rw_lock_n_locked(void)
/*==================*/
{
	rw_lock_t*	lock;
	ulint		count		= 0;
	
	mutex_enter(&rw_lock_list_mutex);

	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)
				|| (rw_lock_get_reader_count(lock) != 0)) {
			count++;
		}

		mutex_exit(rw_lock_get_mutex(lock));
		lock = UT_LIST_GET_NEXT(list, lock);
	}

	mutex_exit(&rw_lock_list_mutex);

	return(count);
}
#endif /* UNIV_SYNC_DEBUG */