Using NSConditionLock - is this correct?

gistfile1.m

@implementation DTDrawingLock
{
	NSUInteger _numberActiveOperations;
	NSConditionLock *_lock;
}

- (instancetype)init
{
	self = [super init];
	
	if (self)
	{
		_lock = [[NSConditionLock alloc] initWithCondition:0];
	}
	
	return self;
}

- (void)pushDrawingOperation
{
	[_lock lock];
	_numberActiveOperations++;
	[_lock unlockWithCondition:_numberActiveOperations];
}

- (void)popDrawingOperations
{
	[_lock lock];
	_numberActiveOperations--;
	[_lock unlockWithCondition:_numberActiveOperations];
}

- (void)performLockProtectedOperation:(void(^)(void))operation
{
	[_lock lockWhenCondition:0];
	
	operation();
	
	[_lock unlockWithCondition:0];
}

@end