#import "ViewController.h"
#import <Pthread.h>

@interface ViewController ()
@property (nonatomic,assign) pthread_rwlock_t lock;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    pthread_rwlock_init(&_lock, NULL);
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    for (int i = 0; i<10; i++) {
        dispatch_async(queue, ^{
            [self read];
        });
        dispatch_async(queue, ^{
            [self read];
        });
        dispatch_async(queue, ^{
            [self write];
        });
    }
}
-(void)read{
    pthread_rwlock_rdlock(&_lock);
    sleep(1);
    NSLog(@"%s",__func__);
    pthread_rwlock_unlock(&_lock);
}
-(void)write{
    pthread_rwlock_wrlock(&_lock);
    sleep(1);
    NSLog(@"%s",__func__);
    pthread_rwlock_unlock(&_lock);
}
-(void)dealloc{
    pthread_rwlock_destroy(&_lock);
}
@end

#import "ViewController.h"

@interface ViewController ()
@property (nonatomic,strong) dispatch_queue_t queue;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.queue = dispatch_queue_create("rw_queue", DISPATCH_QUEUE_CONCURRENT);
    for (int i =0; i<10; i++) {
        dispatch_async(self.queue, ^{
            [self read];
        });
        dispatch_async(self.queue, ^{
            [self read];
        });
        dispatch_barrier_sync(self.queue, ^{
            [self write];
        });
    }
}
-(void)read{
    sleep(1);
    NSLog(@"%s",__func__);
}
-(void)write{
    sleep(1);
    NSLog(@"%s",__func__);
}

@end