iOS多线程方案锁的学习总结

1.OSSpinLock（自旋锁，有优先级翻转问题已摒弃）

//导入头文件
#import <libkern/OSAtomic.h>
//初始化锁
OSSpinLock lock = OS_SPINLOCK_INIT;
//加锁
OSSpinLockLock(&_lock);
//解锁
OSSpinLockUnlock(&_lock);

2.os_unfair_lock（iOS10以后替代OSSpinLock）

//导入头文件
#import <os/lock.h>
//初始化锁
os_unfair_lock lock = OS_UNFAIR_LOCK_INIT;
//加锁
os_unfair_lock_lock(&_lock);
//解锁
os_unfair_lock_unlock(&_lock);

3.pthread_mutex_t（互斥锁）

//导入头文件
#import <pthread.h>
//初始化锁属性
pthread_mutexattr_t mutexattr;
pthread_mutexattr_init(&mutexattr);
pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_NORMAL);
//初始化锁
pthread_mutex_t mutex;
pthread_mutex_init(&_mutex, &mutexattr);
//加锁
pthread_mutex_lock(&_mutex);
//解锁
pthread_mutex_unlock(&_mutex);
//销毁
pthread_mutexattr_destroy(&_mutexattr);
pthread_mutex_destroy(&_mutex);

4.NSLock、NSRecursiveLock

//初始化
self.lock = [[NSLock alloc]init];
//加锁
[self.lock lock];
//解锁
[self.lock unlock];

5.NSCondition、NSConditionLock（条件锁、处理线程依赖场景）

//初始化锁
self.condition = [[NSCondition alloc] init];
//加锁
[self.condition lock];
//条件
if (self.data.count == 0) {
        // 等待（这时锁是解开的状态）
        [self.condition wait];
    }
//信号（唤醒等待）
[self.condition signal];
//解锁
[self.condition unlock];

6.dispatch_semaphore_t（信号量）

dispatch_semaphore_t semaphore = dispatch_semaphore_create(5);
// 如果信号量的值 > 0，就让信号量的值减1，然后继续往下执行代码
// 如果信号量的值 <= 0，就会休眠等待，直到信号量的值变成>0，就让信号量的值减1，然后继续往下执行代码
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
dispatch_semaphore_signal(semaphore);

7.dispatch_queue_t（同步串行队列）

dispatch_queue_t sigQueue = dispatch_queue_create("myQueue", DISPATCH_QUEUE_SERIAL);
dispatch_sync(self.sigQueue, ^{
        ...
});

8.@synchronized

@synchronized([self class]) { 
        ...
} 

总结各种锁性能从高到低