线程互斥与同步

iOS http://www.cnblogs.com/luoguoqiang1985/p/3495800.html
Android http://www.jianshu.com/p/9474d64575b0

• 1.@synchronized对象锁

static NSObject *lockObj = nil;

if (lockObj == nil) {
    lockObj = [[NSObject alloc] init];
}
dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSLog(@"A thread try lock!");
    @synchronized(lockObj)  {
        NSLog(@"A thread lock, please wait!");
        [NSThread sleepForTimeInterval:10];
        NSLog(@"A thread unlock!");
    }
    
});
dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSLog(@"B thread try lock!");
    @synchronized(lockObj)  {
        NSLog(@"B thread lock, please wait!");
        [NSThread sleepForTimeInterval:5];
        NSLog(@"B thread unlock!");
    }
    
});

• 2.NSLock

if (lockMain == nil) {
    lockMain = [[NSLock alloc] init];
}

dispatch_async(dispatch_get_global_queue(0, 0), ^{
    [lockMain lock];
    NSLog(@"A thread begin +!");
    [NSThread sleepForTimeInterval:10];
    NSLog(@"A thread + done and unlock!");
    [lockMain unlock];
    [lockMain lock];
    NSLog(@"A thread begin -!");
    [NSThread sleepForTimeInterval:10];
    NSLog(@"A thread - done and unlock!");
    [lockMain unlock];
});
dispatch_async(dispatch_get_global_queue(0, 0), ^{
    [lockMain lock];
    NSLog(@"B thread begin *!");
    [NSThread sleepForTimeInterval:10];
    NSLog(@"B thread * done and unlock!");
    [lockMain unlock];
    [lockMain lock];
    NSLog(@"B thread begin /!");
    [NSThread sleepForTimeInterval:10];
    NSLog(@"B thread / done and unlock!");
    [lockMain unlock];
});

• 3.NSConditionLock条件锁

static NSConditionLock *cdtLock = nil;
#define A_THREAD  1
#define B_THREAD  2
#define C_THREAD  3

__block NSInteger a = B_THREAD;
if (cdtLock == nil) {
    cdtLock = [[NSConditionLock alloc] initWithCondition:a];
}

dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSLog(@"A thread run!");
    BOOL canLock = [cdtLock tryLockWhenCondition:A_THREAD];
    if (!canLock) {
        NSLog(@"A Thread Lock fail,exit!");
        return ;
    }
    NSLog(@"A thread begin lock!");
    [NSThread sleepForTimeInterval:8];
    NSLog(@"A thread unlock!");
    [cdtLock unlock];
});

dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSLog(@"B thread run!");
    BOOL canLock = [cdtLock tryLockWhenCondition:B_THREAD];
    if (!canLock) {
        NSLog(@"B Thread Lock fail,exit!");
        return ;
    }
    NSLog(@"B thread begin lock!");
    [NSThread sleepForTimeInterval:8];
    NSLog(@"B thread unlock!");
    [cdtLock unlock];
});

dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSLog(@"C thread run!");
    BOOL canLock = [cdtLock tryLockWhenCondition:C_THREAD];
    if (!canLock) {
        NSLog(@"C Thread Lock fail,exit!");
        return ;
    }
    NSLog(@"C thread begin lock!");
    [NSThread sleepForTimeInterval:8];
    NSLog(@"C thread unlock!");
    [cdtLock unlock];
});

• 4.NSRecursiveLock递归锁

static NSRecursiveLock *lock;

 if (lock == nil) {
        lock = [[NSRecursiveLock alloc] init];
    }
    void (^__block DoLog)(int) = ^(int value){
        [lock lock];
        if (value > 0) {
            DoLog(value-1);
        }
        NSLog(@"value is %d", value);
        [lock unlock];
    };
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSLog(@"test begin");
        DoLog(5);
        NSLog(@"test end");
    });