【Linux】线程同步（互斥锁和读写锁）

概念

线程同步是指多个线程之间协调和管理彼此的执行顺序，以避免竞态条件和不确定的结果。线程同步的目的是确保共享资源的正确访问和保护临界区的完整性。

作用

• 避免竞态条件：当多个线程同时访问和修改共享资源时，可能会导致竞态条件的发生。竞态条件指的是多个线程之间的执行顺序和时序不确定，导致结果的不确定性和不正确性。使用线程同步机制可以避免竞态条件的发生，保证共享资源的正确访问顺序，从而避免不确定的结果。
• 保护临界区：临界区是指在多线程环境中访问共享资源的代码段。在临界区中，只允许一个线程访问共享资源，其他线程需要等待。通过使用线程同步机制，比如互斥锁或读写锁，可以保护临界区的完整性，确保同时只有一个线程可以进入临界区，避免数据的不一致和错误的操作。
• 实现线程间的协作和通信：在某些情况下，多个线程需要相互协作完成某个任务，或者进行线程间的通信和数据交换。线程同步机制，如条件变量、信号量和屏障，可以提供线程间的等待和通知机制，确保线程在适当的时机等待或继续执行，从而实现线程间的协作和通信。
• 提高性能和效率：在某些情况下，合理使用线程同步机制可以提高多线程程序的性能和效率。例如，在读写操作频繁的场景中，使用读写锁可以允许多个线程同时进行读操作，提高并发性能。此外，使用原子操作可以避免显式的锁竞争，提高程序的执行效率。

使用线程同步机制可以确保多线程程序的正确性、安全性和可靠性。它能够解决多线程并发访问共享资源时可能出现的问题，并提供了一种有效的方式来协调和管理多个线程的执行。

线程同步的方式

• 互斥锁（Mutex）：

  互斥锁用于保护临界区资源，确保在任意时刻只有一个线程可以访问被保护的资源。当一个线程获得互斥锁后，其他线程需要等待直到该线程释放锁。

• 读写锁（Read-Write Lock）：

  读写锁允许多个线程同时对共享资源进行读操作，但只允许一个线程进行写操作。这样可以提高读操作的并发性能。

• 条件变量（Condition Variable）：

  条件变量用于线程之间的等待和通知机制。一个线程可以在条件变量上等待，直到其他线程满足某个条件后通知等待的线程。

• 信号量（Semaphore）：

  信号量用于控制对共享资源的访问和线程的并发数量。它可以用于限制并发线程的数量或者实现互斥和同步。

互斥锁

互斥锁是线程同步最常用的一种方式，通过互斥锁可以锁定一个代码块，被锁定的这个代码块，所有的线程只能顺序执行(不能并行处理)，这样多线程访问共享资源数据混乱的问题就可以被解决了，需要付出的代价就是执行效率的降低，因为默认临界区多个线程是可以并行处理的，现在只能串行处理。

互斥锁的使用

• 在 Linux 中互斥锁的类型为 pthread_mutex_t，创建一个这种类型的变量就得到了一把互斥锁：

pthread_mutex_t  mutex;

一个互斥锁变量只能被一个线程锁定，被锁定之后其他线程再对互斥锁变量加锁就会被阻塞，直到这把互斥锁被解锁，被阻塞的线程才能被解除阻塞。

一般情况下，每一个共享资源对应一个把互斥锁，锁的个数和线程的个数无关。

初始化互斥锁

int pthread_mutex_init(pthread_mutex_t *restrict mutex,const pthread_mutexattr_t *restrict attr);

restrict 是 C 语言中的一个关键字，用于指示指针是唯一访问某个数据对象的指针，这意味着在指针的生命周期内，没有其他别名指针可以访问相同的数据对象。

释放互斥锁

int pthread_mutex_destroy(pthread_mutex_t *mutex);

其中mutex是互斥锁变量的地址。

加锁和解锁

int pthread_mutex_lock(pthread_mutex_t *mutex);

修改互斥锁的状态, 将其设定为锁定状态, 这个状态被写入到参数 mutex 中。

该函数首先会判断参数 mutex 互斥锁中的状态是不是锁定状态:
没有被锁定，是打开的，这个线程可以加锁成功，这个这个锁中会记录是哪个线程加锁成功了
如果被锁定了，其他线程加锁就失败了，这些线程都会阻塞在这把锁上
当这把锁被解开之后，这些阻塞在锁上的线程就解除阻塞了，并且这些线程是通过竞争的方式对这把锁加锁，没抢到锁的线程继续阻塞。

当某一线程加上互斥锁后，可以看作该互斥锁已被这个线程持有，该线程可以对锁中的全局变量进行修改访问，其他线程无法获取互斥锁，即无法对共享资源进行访问。

不是所有的线程都可以对互斥锁解锁，哪个线程加的锁，哪个线程才能解锁成功。

示例

下面给出一段代码，创建两个线程、两线程交替数数，每个线程数50个数，交替数到100。

#include
#include
#include
#include
#include
#include
#include 
#define MAX 50
int number;
pthread_mutex_t mutex;
void* fun1(void *arg)
{
for(int i=0;i<MAX;++i)
{
int cur=number;
cur++;
usleep(10);
number=cur;
printf("Thread A,id = %lu,number=%d\n",pthread_self(),number);
}
return NULL;
}

void* fun2(void *arg)
{
for(int i=0;i<MAX;++i)
{
int cur=number;
cur++;
number=cur;
usleep(10);
printf("Thread B,id = %lu,number=%d\n",pthread_self(),number);
}
return NULL;
}

int main(int argc,const char* argv[])
{
pthread_mutex_init(&mutex,NULL);
pthread_t  p1,p2;
pthread_create(&p1,NULL,fun1,NULL);
pthread_create(&p2,NULL,fun2,NULL);
pthread_join(p1,NULL);
pthread_join(p2,NULL);
pthread_mutex_destroy(&mutex);
return 0;
}

结果如下所示：

Thread A,id = 139713615181568,number=1
Thread B,id = 139713606788864,number=1
Thread B,id = 139713606788864,number=2
Thread A,id = 139713615181568,number=2
Thread B,id = 139713606788864,number=2
Thread A,id = 139713615181568,number=3
Thread B,id = 139713606788864,number=3
Thread A,id = 139713615181568,number=4
Thread B,id = 139713606788864,number=4
Thread A,id = 139713615181568,number=5
Thread B,id = 139713606788864,number=5
Thread A,id = 139713615181568,number=6
Thread A,id = 139713615181568,number=7
Thread B,id = 139713606788864,number=7
Thread B,id = 139713606788864,number=8
Thread A,id = 139713615181568,number=8
Thread A,id = 139713615181568,number=9
Thread B,id = 139713606788864,number=9
Thread B,id = 139713606788864,number=10
Thread A,id = 139713615181568,number=10
Thread A,id = 139713615181568,number=11
Thread B,id = 139713606788864,number=11
Thread B,id = 139713606788864,number=12
Thread A,id = 139713615181568,number=12
Thread A,id = 139713615181568,number=13
Thread B,id = 139713606788864,number=13
Thread B,id = 139713606788864,number=14
Thread A,id = 139713615181568,number=14
Thread A,id = 139713615181568,number=15
Thread B,id = 139713606788864,number=15
Thread B,id = 139713606788864,number=16
Thread A,id = 139713615181568,number=16
Thread A,id = 139713615181568,number=17
Thread B,id = 139713606788864,number=17
Thread A,id = 139713615181568,number=18
Thread B,id = 139713606788864,number=18
Thread B,id = 139713606788864,number=19
Thread A,id = 139713615181568,number=19
Thread B,id = 139713606788864,number=19
Thread A,id = 139713615181568,number=20
Thread A,id = 139713615181568,number=21
Thread B,id = 139713606788864,number=21
Thread A,id = 139713615181568,number=22
Thread B,id = 139713606788864,number=22
Thread B,id = 139713606788864,number=23
Thread A,id = 139713615181568,number=23
Thread A,id = 139713615181568,number=24
Thread B,id = 139713606788864,number=24
Thread B,id = 139713606788864,number=25
Thread A,id = 139713615181568,number=25
Thread A,id = 139713615181568,number=26
Thread B,id = 139713606788864,number=26
Thread B,id = 139713606788864,number=27
Thread A,id = 139713615181568,number=27
Thread A,id = 139713615181568,number=28
Thread B,id = 139713606788864,number=28
Thread B,id = 139713606788864,number=29
Thread A,id = 139713615181568,number=29
Thread A,id = 139713615181568,number=30
Thread B,id = 139713606788864,number=30
Thread B,id = 139713606788864,number=31
Thread A,id = 139713615181568,number=31
Thread A,id = 139713615181568,number=32
Thread B,id = 139713606788864,number=32
Thread B,id = 139713606788864,number=33
Thread A,id = 139713615181568,number=33
Thread A,id = 139713615181568,number=34
Thread B,id = 139713606788864,number=34
Thread B,id = 139713606788864,number=35
Thread A,id = 139713615181568,number=35
Thread A,id = 139713615181568,number=36
Thread B,id = 139713606788864,number=36
Thread B,id = 139713606788864,number=37
Thread A,id = 139713615181568,number=37
Thread A,id = 139713615181568,number=38
Thread B,id = 139713606788864,number=38
Thread B,id = 139713606788864,number=39
Thread A,id = 139713615181568,number=39
Thread A,id = 139713615181568,number=40
Thread B,id = 139713606788864,number=40
Thread B,id = 139713606788864,number=41
Thread A,id = 139713615181568,number=41
Thread A,id = 139713615181568,number=42
Thread B,id = 139713606788864,number=42
Thread B,id = 139713606788864,number=43
Thread A,id = 139713615181568,number=43
Thread A,id = 139713615181568,number=44
Thread B,id = 139713606788864,number=44
Thread B,id = 139713606788864,number=45
Thread A,id = 139713615181568,number=45
Thread A,id = 139713615181568,number=46
Thread B,id = 139713606788864,number=46
Thread B,id = 139713606788864,number=47
Thread A,id = 139713615181568,number=47
Thread A,id = 139713615181568,number=48
Thread B,id = 139713606788864,number=48
Thread B,id = 139713606788864,number=49
Thread A,id = 139713615181568,number=49
Thread A,id = 139713615181568,number=50
Thread B,id = 139713606788864,number=50

在代码中，两个线程fun1和fun2都对number进行了读取和修改操作，而没有进行同步控制，导致它们可能同时访问和修改number，从而引发竞态条件（Race Condition）问题。

为了解决这个问题，可以在对number的读取和修改操作之前加上互斥锁的加锁和解锁操作，以确保每次只有一个线程在访问和修改number。

#include
#include
#include
#include
#include
#include
#include
#define MAX 50
int number;
pthread_mutex_t mutex;
void print_mutex_type() {
    int type;
    pthread_mutexattr_t attr;
    pthread_mutexattr_init(&attr);
    pthread_mutexattr_gettype(&attr, &type);

    if (type == PTHREAD_MUTEX_NORMAL)
        printf("Mutex Type: Normal Mutex\n");
    else if (type == PTHREAD_MUTEX_RECURSIVE)
        printf("Mutex Type: Recursive Mutex\n");
    else if (type == PTHREAD_MUTEX_ERRORCHECK)
        printf("Mutex Type: Error-Checking Mutex\n");
    else
        printf("Mutex Type: Unknown\n");

    pthread_mutexattr_destroy(&attr);
}
void* fun1(void *arg)
{
for(int i=0;i<MAX;++i)
{
pthread_mutex_lock(&mutex);
int cur=number;
cur++;
usleep(10);
number=cur;
printf("Thread A,id = %lu,number=%d\n",pthread_self(),number);
pthread_mutex_unlock(&mutex);
}
return NULL;
}
void* fun2(void *arg)
{
for(int i=0;i<MAX;++i)
{
pthread_mutex_lock(&mutex);
int cur=number;
cur++;
number=cur;
usleep(10);
printf("Thread B,id = %lu,number=%d\n",pthread_self(),number);
pthread_mutex_unlock(&mutex);
}
return NULL;
}
int main(int argc,const char* argv[])
{
print_mutex_type();
pthread_mutex_init(&mutex,NULL);
pthread_t  p1,p2;
pthread_create(&p1,NULL,fun1,NULL);
pthread_create(&p2,NULL,fun2,NULL);
pthread_join(p1,NULL);
pthread_join(p2,NULL);
pthread_mutex_destroy(&mutex);
return 0;
}

运行结果如下所示：

Thread A,id = 139723581155072,number=1
Thread A,id = 139723581155072,number=2
Thread A,id = 139723581155072,number=3
Thread A,id = 139723581155072,number=4
Thread A,id = 139723581155072,number=5
Thread A,id = 139723581155072,number=6
Thread A,id = 139723581155072,number=7
Thread A,id = 139723581155072,number=8
Thread A,id = 139723581155072,number=9
Thread A,id = 139723581155072,number=10
Thread A,id = 139723581155072,number=11
Thread A,id = 139723581155072,number=12
Thread A,id = 139723581155072,number=13
Thread A,id = 139723581155072,number=14
Thread A,id = 139723581155072,number=15
Thread A,id = 139723581155072,number=16
Thread A,id = 139723581155072,number=17
Thread A,id = 139723581155072,number=18
Thread A,id = 139723581155072,number=19
Thread A,id = 139723581155072,number=20
Thread A,id = 139723581155072,number=21
Thread A,id = 139723581155072,number=22
Thread A,id = 139723581155072,number=23
Thread A,id = 139723581155072,number=24
Thread A,id = 139723581155072,number=25
Thread A,id = 139723581155072,number=26
Thread A,id = 139723581155072,number=27
Thread A,id = 139723581155072,number=28
Thread A,id = 139723581155072,number=29
Thread A,id = 139723581155072,number=30
Thread A,id = 139723581155072,number=31
Thread A,id = 139723581155072,number=32
Thread A,id = 139723581155072,number=33
Thread A,id = 139723581155072,number=34
Thread A,id = 139723581155072,number=35
Thread A,id = 139723581155072,number=36
Thread A,id = 139723581155072,number=37
Thread A,id = 139723581155072,number=38
Thread A,id = 139723581155072,number=39
Thread A,id = 139723581155072,number=40
Thread A,id = 139723581155072,number=41
Thread A,id = 139723581155072,number=42
Thread A,id = 139723581155072,number=43
Thread A,id = 139723581155072,number=44
Thread A,id = 139723581155072,number=45
Thread A,id = 139723581155072,number=46
Thread A,id = 139723581155072,number=47
Thread A,id = 139723581155072,number=48
Thread A,id = 139723581155072,number=49
Thread A,id = 139723581155072,number=50
Thread B,id = 139723572762368,number=51
Thread B,id = 139723572762368,number=52
Thread B,id = 139723572762368,number=53
Thread B,id = 139723572762368,number=54
Thread B,id = 139723572762368,number=55
Thread B,id = 139723572762368,number=56
Thread B,id = 139723572762368,number=57
Thread B,id = 139723572762368,number=58
Thread B,id = 139723572762368,number=59
Thread B,id = 139723572762368,number=60
Thread B,id = 139723572762368,number=61
Thread B,id = 139723572762368,number=62
Thread B,id = 139723572762368,number=63
Thread B,id = 139723572762368,number=64
Thread B,id = 139723572762368,number=65
Thread B,id = 139723572762368,number=66
Thread B,id = 139723572762368,number=67
Thread B,id = 139723572762368,number=68
Thread B,id = 139723572762368,number=69
Thread B,id = 139723572762368,number=70
Thread B,id = 139723572762368,number=71
Thread B,id = 139723572762368,number=72
Thread B,id = 139723572762368,number=73
Thread B,id = 139723572762368,number=74
Thread B,id = 139723572762368,number=75
Thread B,id = 139723572762368,number=76
Thread B,id = 139723572762368,number=77
Thread B,id = 139723572762368,number=78
Thread B,id = 139723572762368,number=79
Thread B,id = 139723572762368,number=80
Thread B,id = 139723572762368,number=81
Thread B,id = 139723572762368,number=82
Thread B,id = 139723572762368,number=83
Thread B,id = 139723572762368,number=84
Thread B,id = 139723572762368,number=85
Thread B,id = 139723572762368,number=86
Thread B,id = 139723572762368,number=87
Thread B,id = 139723572762368,number=88
Thread B,id = 139723572762368,number=89
Thread B,id = 139723572762368,number=90
Thread B,id = 139723572762368,number=91
Thread B,id = 139723572762368,number=92
Thread B,id = 139723572762368,number=93
Thread B,id = 139723572762368,number=94
Thread B,id = 139723572762368,number=95
Thread B,id = 139723572762368,number=96
Thread B,id = 139723572762368,number=97
Thread B,id = 139723572762368,number=98
Thread B,id = 139723572762368,number=99
Thread B,id = 139723572762368,number=100

读写锁

读写锁是互斥锁的升级版，在做读操作的时候可以提高程序的执行效率，如果所有的线程都是做读操作, 那么读是并行的，但是使用互斥锁，读操作也是串行的。

读写锁的使用

读写锁是一把锁，锁的类型为 pthread_rwlock_t，有了类型之后就可以创建一把读写锁了，其创建、销毁、加锁解锁方式与互斥锁类似：

pthread_rwlock_t rwlock;

读写锁类型为pthread_rwlock_t，它并不能分为读锁和写锁，但是可以进行读操作锁定和写操作锁定。

读写锁初始化及释放

int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,
           const pthread_rwlockattr_t *restrict attr);

int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);

加读锁

int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);

调用这个函数，如果读写锁是打开的，那么加锁成功；如果读写锁已经锁定了读操作，调用这个函数依然可以加锁成功，因为读锁是共享的；如果读写锁已经锁定了写操作，调用这个函数的线程会被阻塞

加写锁

int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

调用这个函数，如果读写锁是打开的，那么加锁成功；如果读写锁已经锁定了读操作或者锁定了写操作，调用这个函数的线程会被阻塞。

解锁

int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);

不管锁定了读还是写都可用该函数进行解锁。

示例

8 个线程操作同一个全局变量，3 个线程不定时写同一全局资源，5 个线程不定时读同一全局资源。

#include
#include
#include
#include
#include
#include
#include

#define MAX 50
int number;
pthread_rwlock_t rw;
void* read_num(void* arg)
{
for(int i=0;i<MAX;i++)
{
pthread_rwlock_rdlock(&rw);
printf("Thread read,id=%lu,number=%d\n",pthread_self(),number);
pthread_rwlock_unlock(&rw);
usleep(rand()%5);
}
return NULL;
}
void* write_num(void* arg)
{
for(int i=0;i<MAX;i++)
{
pthread_rwlock_wrlock(&rw);
int cur=number;
cur++;
usleep(15);
number=cur;
printf("Thread write,id = %lu,number=%d\n",pthread_self(),number);

pthread_rwlock_unlock(&rw);
usleep(rand()%5);
}
return NULL;
}

int main(int argc,const char* argv[])
{

pthread_rwlock_init(&rw,NULL);

pthread_t  p1[5],p2[3];
for(int i=0;i<5;i++)
{
pthread_create(&p1[i],NULL,read_num,NULL);
}
for(int i=0;i<3;i++)
{
pthread_create(&p2[i],NULL,write_num,NULL);
}

for(int i=0;i<3;i++)
{
pthread_join(p2[i],NULL);
}
for(int i=0;i<5;i++)
{
pthread_join(p1[i],NULL);
}

pthread_rwlock_destroy(&rw);
return 0;
}

运行结果如下所示：

Thread read,id=139752767919872,number=0
Thread read,id=139752759527168,number=0
Thread read,id=139752751134464,number=0
Thread read,id=139752742741760,number=0
Thread read,id=139752734349056,number=0
Thread write,id = 139752725956352,number=1
Thread write,id = 139752717563648,number=2
Thread write,id = 139752709170944,number=3
Thread write,id = 139752725956352,number=4
Thread write,id = 139752717563648,number=5
Thread write,id = 139752709170944,number=6
Thread write,id = 139752725956352,number=7
Thread write,id = 139752717563648,number=8
Thread write,id = 139752725956352,number=9
Thread write,id = 139752709170944,number=10
Thread write,id = 139752717563648,number=11
Thread write,id = 139752725956352,number=12
Thread write,id = 139752709170944,number=13
Thread write,id = 139752717563648,number=14
Thread write,id = 139752725956352,number=15
Thread write,id = 139752709170944,number=16
Thread write,id = 139752717563648,number=17
Thread write,id = 139752725956352,number=18
Thread write,id = 139752709170944,number=19
Thread write,id = 139752717563648,number=20
Thread write,id = 139752725956352,number=21
Thread write,id = 139752709170944,number=22
Thread write,id = 139752717563648,number=23
Thread write,id = 139752725956352,number=24
Thread write,id = 139752709170944,number=25
Thread write,id = 139752717563648,number=26
Thread write,id = 139752725956352,number=27
Thread write,id = 139752709170944,number=28
Thread write,id = 139752717563648,number=29
Thread write,id = 139752725956352,number=30
Thread write,id = 139752709170944,number=31
Thread write,id = 139752717563648,number=32
Thread write,id = 139752725956352,number=33
Thread write,id = 139752709170944,number=34
Thread write,id = 139752725956352,number=35
Thread write,id = 139752717563648,number=36
Thread write,id = 139752709170944,number=37
Thread write,id = 139752725956352,number=38
Thread write,id = 139752717563648,number=39
Thread write,id = 139752709170944,number=40
Thread write,id = 139752725956352,number=41
Thread write,id = 139752717563648,number=42
Thread write,id = 139752709170944,number=43
Thread write,id = 139752725956352,number=44
Thread write,id = 139752717563648,number=45
Thread write,id = 139752709170944,number=46
Thread write,id = 139752725956352,number=47
Thread write,id = 139752717563648,number=48
Thread write,id = 139752709170944,number=49
Thread write,id = 139752725956352,number=50
Thread write,id = 139752717563648,number=51
Thread write,id = 139752725956352,number=52
Thread write,id = 139752709170944,number=53
Thread write,id = 139752717563648,number=54
Thread write,id = 139752725956352,number=55
Thread write,id = 139752709170944,number=56
Thread write,id = 139752717563648,number=57
Thread write,id = 139752725956352,number=58
Thread write,id = 139752709170944,number=59
Thread write,id = 139752717563648,number=60
Thread write,id = 139752725956352,number=61
Thread write,id = 139752709170944,number=62
Thread write,id = 139752717563648,number=63
Thread write,id = 139752709170944,number=64
Thread write,id = 139752717563648,number=65
Thread write,id = 139752725956352,number=66
Thread write,id = 139752709170944,number=67
Thread write,id = 139752717563648,number=68
Thread write,id = 139752725956352,number=69
Thread write,id = 139752709170944,number=70
Thread write,id = 139752717563648,number=71
Thread write,id = 139752725956352,number=72
Thread write,id = 139752709170944,number=73
Thread write,id = 139752717563648,number=74
Thread write,id = 139752725956352,number=75
Thread write,id = 139752709170944,number=76
Thread write,id = 139752717563648,number=77
Thread write,id = 139752725956352,number=78
Thread write,id = 139752709170944,number=79
Thread write,id = 139752717563648,number=80
Thread write,id = 139752725956352,number=81
Thread write,id = 139752709170944,number=82
Thread write,id = 139752717563648,number=83
Thread write,id = 139752725956352,number=84
Thread write,id = 139752709170944,number=85
Thread write,id = 139752717563648,number=86
Thread write,id = 139752725956352,number=87
Thread write,id = 139752709170944,number=88
Thread write,id = 139752717563648,number=89
Thread write,id = 139752725956352,number=90
Thread write,id = 139752709170944,number=91
Thread write,id = 139752717563648,number=92
Thread write,id = 139752725956352,number=93
Thread write,id = 139752709170944,number=94
Thread write,id = 139752717563648,number=95
Thread write,id = 139752725956352,number=96
Thread write,id = 139752709170944,number=97
Thread write,id = 139752717563648,number=98
Thread write,id = 139752725956352,number=99
Thread write,id = 139752709170944,number=100
Thread write,id = 139752717563648,number=101
Thread write,id = 139752725956352,number=102
Thread write,id = 139752709170944,number=103
Thread write,id = 139752717563648,number=104
Thread write,id = 139752725956352,number=105
Thread write,id = 139752709170944,number=106
Thread write,id = 139752717563648,number=107
Thread write,id = 139752725956352,number=108
Thread write,id = 139752709170944,number=109
Thread write,id = 139752717563648,number=110
Thread write,id = 139752725956352,number=111
Thread write,id = 139752717563648,number=112
Thread write,id = 139752709170944,number=113
Thread write,id = 139752725956352,number=114
Thread write,id = 139752717563648,number=115
Thread write,id = 139752709170944,number=116
Thread write,id = 139752725956352,number=117
Thread write,id = 139752709170944,number=118
Thread write,id = 139752717563648,number=119
Thread write,id = 139752725956352,number=120
Thread write,id = 139752709170944,number=121
Thread write,id = 139752717563648,number=122
Thread write,id = 139752725956352,number=123
Thread write,id = 139752709170944,number=124
Thread write,id = 139752717563648,number=125
Thread write,id = 139752725956352,number=126
Thread write,id = 139752709170944,number=127
Thread write,id = 139752717563648,number=128
Thread write,id = 139752725956352,number=129
Thread write,id = 139752709170944,number=130
Thread write,id = 139752717563648,number=131
Thread write,id = 139752725956352,number=132
Thread write,id = 139752709170944,number=133
Thread write,id = 139752717563648,number=134
Thread write,id = 139752725956352,number=135
Thread write,id = 139752709170944,number=136
Thread write,id = 139752717563648,number=137
Thread write,id = 139752725956352,number=138
Thread write,id = 139752709170944,number=139
Thread write,id = 139752717563648,number=140
Thread write,id = 139752725956352,number=141
Thread write,id = 139752709170944,number=142
Thread write,id = 139752717563648,number=143
Thread write,id = 139752725956352,number=144
Thread write,id = 139752709170944,number=145
Thread write,id = 139752717563648,number=146
Thread write,id = 139752725956352,number=147
Thread write,id = 139752709170944,number=148
Thread write,id = 139752717563648,number=149
Thread read,id=139752759527168,number=149
Thread read,id=139752751134464,number=149
Thread read,id=139752767919872,number=149
Thread read,id=139752742741760,number=149
Thread read,id=139752734349056,number=149
Thread write,id = 139752709170944,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752767919872,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752742741760,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752751134464,number=150
Thread read,id=139752759527168,number=150
Thread read,id=139752734349056,number=150
Thread read,id=139752767919872,number=150

可以看到，读操作可以同步进行，写操作只能串行进行。

读线程可以同时进行读取操作，但不能与写线程同时进行写操作，以保证数据的一致性和线程的安全性。