linux Posix线程同步(条件变量) 实例
条件变量：与互斥量一起使用，暂时申请不到某资源时进入条件阻塞等待，当资源具备时线程恢复运行
应用场合：生产线程不断的生产资源，并通知产生资源的条件，消费线程在没有资源情况下进入条件等待，一直等到条件信号的产生
主要函数有两个：
1)等待条件
int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
2)发送条件信号
int pthread_cond_signal(pthread_cond_t *cond);
请参考：
http://www.diybl.com/course/3_program/c++/cppjs/20110518/555794.html
http://www.ibm.com/developerworks/cn/linux/thread/posix_threadapi/part3/
编译：
gcc -o pthread pthread.c -lpthread
/*单个生产者和单个消费者*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#define BUFFER_SIZE 5 //产品库存大小
#define PRODUCT_CNT 50 //产品生产总数
struct product_cons
{
int buffer[BUFFER_SIZE]; //生产产品值
pthread_mutex_t lock; //互斥锁 volatile int
int readpos, writepos; //读写位置
pthread_cond_t notempty; //条件变量，非空
pthread_cond_t notfull; //非满
}buffer;
void init(struct product_cons *p)
{
pthread_mutex_init(&p->lock, NULL); //互斥锁
pthread_cond_init(&p->notempty, NULL); //条件变量
pthread_cond_init(&p->notfull, NULL); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
}
void fini(struct product_cons *p)
{
pthread_mutex_destroy(&p->lock); //互斥锁
pthread_cond_destroy(&p->notempty); //条件变量
pthread_cond_destroy(&p->notfull); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
}
void cleanup_handler(void *arg)
{
printf("cleanup_handler exec!\n");
pthread_mutex_t *lock = (pthread_mutex_t*)arg;
pthread_mutex_unlock(lock); //解锁
}
//存储 一个数据 到 bufferr
void put(struct product_cons *p, int data) //输入产品子函数
{
pthread_mutex_lock(&p->lock); //上锁
/*等待，直到 buffer 不为 满*/
while((p->writepos + 1) % BUFFER_SIZE == p->readpos) //测试空间是否已满
{
printf("producer wait for not full\n");
pthread_cond_wait(&p->notfull, &p->lock); //阻塞等待
//这里，生产者 notfull 等待消费者 pthread_cond_signal(&p->notfull);信号
//如果，消费者发送了 signal 信号，表示有了 空闲
}
p->buffer[p->writepos] = data; //写数据
p->writepos++;
if(p->writepos >= BUFFER_SIZE) //如果写到 尾部,返回
p->writepos = 0;
pthread_cond_signal(&p->notempty); //发送有数据信号
pthread_mutex_unlock(&p->lock); //解锁
}
//读，移除 一个数据 从 buffer
int get(struct product_cons *p)
{
int data = 0;
pthread_mutex_lock(&p->lock);
/*等待，直到不为空*/
while(p->writepos == p->readpos)
{
printf("consumer wait for not empty\n");
pthread_cond_wait(&p->notempty,&p->lock);
}
/*读 一个 数据*/
data = p->buffer[p->readpos];
p->readpos++;
if(p->readpos >= BUFFER_SIZE) //如果读到 尾
p->readpos = 0;
pthread_cond_signal(&p->notfull);
pthread_mutex_unlock(&p->lock);
return data;
}
void *producer(void *data) //子线程 ，生产
{
int n;
for(n = 1; n <= 50; ++n) //生产 50 个产品
{
sleep(1);
printf("put the %d product\n",n);
put(&buffer,n);
}
printf("producer stopped\n");
return NULL;
}
void *consumer(void *data)
{
static int cnt = 0;
while(1)
{
sleep(2);
printf("get the %d product\n", get(&buffer));
if(++cnt == PRODUCT_CNT)
break;
}
printf("consumer stopped\n");
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t th_a,th_b;
void *retval;
init(&buffer);
pthread_create(&th_a, NULL, producer, 0);
pthread_create(&th_b, NULL, consumer, 0);
pthread_join(th_a, &retval);
pthread_join(th_b, &retval);
fini(&buffer);
return 0;
}
/*多个生产者和单个消费者*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#define BUFFER_SIZE 5 //产品库存大小
#define PRODUCT_CNT 50 //产品生产总数
struct product_cons
{
int buffer[BUFFER_SIZE]; //生产产品值
pthread_mutex_t lock; //互斥锁，控制buffer
int readpos, writepos; //读写位置
pthread_cond_t notempty; //条件变量，非空
pthread_cond_t notfull; //非满
pthread_mutex_t lock2; //互斥锁，控制cnt
int cnt; //完成生产产品数量
}buffer;
void init(struct product_cons *p)
{
pthread_mutex_init(&p->lock, NULL); //互斥锁
pthread_cond_init(&p->notempty, NULL); //条件变量
pthread_cond_init(&p->notfull, NULL); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_init(&p->lock2, NULL);
p->cnt = 0;
}
void fini(struct product_cons *p)
{
pthread_mutex_destroy(&p->lock); //互斥锁
pthread_cond_destroy(&p->notempty); //条件变量
pthread_cond_destroy(&p->notfull); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_destroy(&p->lock2);
p->cnt = 0;
}
//存储 一个数据 到 bufferr
void put(struct product_cons *p, int data) //输入产品子函数
{
pthread_mutex_lock(&p->lock); //上锁
/*等待，直到 buffer 不为 满*/
while((p->writepos + 1) % BUFFER_SIZE == p->readpos) //测试空间是否已满
{
printf("producer wait for not full\n");
pthread_cond_wait(&p->notfull, &p->lock); //阻塞等待
//这里，生产者 notfull 等待消费者 pthread_cond_signal(&p->notfull);信号
//如果，消费者发送了 signal 信号，表示有了 空闲
}
p->buffer[p->writepos] = data; //写数据
p->writepos++;
if(p->writepos >= BUFFER_SIZE) //如果写到 尾部,返回
p->writepos = 0;
pthread_cond_signal(&p->notempty); //发送有数据信号
pthread_mutex_unlock(&p->lock); //解锁
}
//读，移除 一个数据 从 buffer
int get(struct product_cons *p)
{
int data = 0;
pthread_mutex_lock(&p->lock);
/*等待，直到不为空*/
while(p->writepos == p->readpos)
{
printf("consumer wait for not empty\n");
pthread_cond_wait(&p->notempty,&p->lock);
}
/*读 一个 数据*/
data = p->buffer[p->readpos];
p->readpos++;
if(p->readpos >= BUFFER_SIZE) //如果读到 尾
p->readpos = 0;
pthread_cond_signal(&p->notfull);
pthread_mutex_unlock(&p->lock);
return data;
}
void *producer(void *data) //子线程 ，生产
{
int flag = -1;
while(1)
{
pthread_mutex_lock(&buffer.lock2);
if(buffer.cnt < PRODUCT_CNT)
{
++buffer.cnt;
printf("%s put the %d product\n", (char*)data, buffer.cnt);
put(&buffer, buffer.cnt);
}
else
flag = 0;
pthread_mutex_unlock(&buffer.lock2);
if(!flag)
break;
sleep(2);
}
printf("%s producer stopped\n", (char*)data);
return NULL;
}
void *consumer(void *data)
{
int d = 0;
while(1)
{
sleep(1);
d = get(&buffer);
printf("get the %d product\n",d);
if(d == PRODUCT_CNT)
break;
}
printf("consumer stopped\n");
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t th_a[3],th_b;
void *retval;
init(&buffer);
pthread_create(&th_a[0], NULL, producer, (void*)"th_a[0]");
pthread_create(&th_a[1], NULL, producer, (void*)"th_a[1]");
pthread_create(&th_a[2], NULL, producer, (void*)"th_a[2]");
pthread_create(&th_b, NULL, consumer, 0);
pthread_join(th_a[0], &retval);
pthread_join(th_a[1], &retval);
pthread_join(th_a[2], &retval);
pthread_join(th_b, &retval);
fini(&buffer);
return 0;
}
/*单个生产者和多个消费者*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#define BUFFER_SIZE 5 //产品库存大小
#define PRODUCT_CNT 50 //产品生产总数
struct product_cons
{
int buffer[BUFFER_SIZE]; //生产产品值
pthread_mutex_t lock; //互斥锁 volatile int
int readpos, writepos; //读写位置
pthread_cond_t notempty; //条件变量，非空
pthread_cond_t notfull; //非满
pthread_mutex_t lock2; //互斥锁，控制cnt
int cnt; //获得生产产品数量
}buffer;
void init(struct product_cons *p)
{
pthread_mutex_init(&p->lock, NULL); //互斥锁
pthread_cond_init(&p->notempty, NULL); //条件变量
pthread_cond_init(&p->notfull, NULL); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_init(&p->lock2, NULL);
p->cnt = 0;
}
void fini(struct product_cons *p)
{
pthread_mutex_destroy(&p->lock); //互斥锁
pthread_cond_destroy(&p->notempty); //条件变量
pthread_cond_destroy(&p->notfull); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_destroy(&p->lock2);
p->cnt = 0;
}
//存储 一个数据 到 bufferr
void put(struct product_cons *p, int data) //输入产品子函数
{
pthread_mutex_lock(&p->lock); //上锁
/*等待，直到 buffer 不为 满*/
while((p->writepos + 1) % BUFFER_SIZE == p->readpos) //测试空间是否已满
{
printf("producer wait for not full\n");
pthread_cond_wait(&p->notfull, &p->lock); //阻塞等待
//这里，生产者 notfull 等待消费者 pthread_cond_signal(&p->notfull);信号
//如果，消费者发送了 signal 信号，表示有了 空闲
}
p->buffer[p->writepos] = data; //写数据
p->writepos++;
if(p->writepos >= BUFFER_SIZE) //如果写到 尾部,返回
p->writepos = 0;
pthread_cond_signal(&p->notempty); //发送有数据信号
pthread_mutex_unlock(&p->lock); //解锁
}
//读，移除 一个数据 从 buffer
int get(struct product_cons *p)
{
int data = 0;
pthread_mutex_lock(&p->lock);
/*等待，直到不为空*/
while(p->writepos == p->readpos)
{
printf("consumer wait for not empty\n");
pthread_cond_wait(&p->notempty,&p->lock);
}
/*读 一个 数据*/
data = p->buffer[p->readpos];
p->readpos++;
if(p->readpos >= BUFFER_SIZE) //如果读到 尾
p->readpos = 0;
pthread_cond_signal(&p->notfull);
pthread_mutex_unlock(&p->lock);
return data;
}
void *producer(void *data) //子线程 ，生产
{
int n;
for(n = 1; n <= PRODUCT_CNT; ++n) //生产 50 个产品
{
sleep(1);
printf("put the %d product\n",n);
put(&buffer, n);
}
printf("producer stopped\n");
return NULL;
}
void *consumer(void *data)
{
int flag = -1;
while(1)
{
pthread_mutex_lock(&buffer.lock2);
if(buffer.cnt < PRODUCT_CNT)
{
printf("%s get the %d product\n", (char*)data, get(&buffer));
++buffer.cnt;
}
else
flag = 0;
pthread_mutex_unlock(&buffer.lock2);
if(!flag)
break;
sleep(2);
}
printf("%s consumer stopped\n", (char*)data);
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t th_a,th_b[3];
void *retval;
init(&buffer);
pthread_create(&th_a, NULL, producer, 0);
pthread_create(&th_b[0], NULL, consumer, (void*)"th_b[0]");
pthread_create(&th_b[1], NULL, consumer, (void*)"th_b[1]");
pthread_create(&th_b[2], NULL, consumer, (void*)"th_b[2]");
pthread_join(th_a, &retval);
pthread_join(th_b[0], &retval);
pthread_join(th_b[1], &retval);
pthread_join(th_b[2], &retval);
fini(&buffer);
return 0;
}
/*多个生产者和多个消费者*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>
#define BUFFER_SIZE 5 //产品库存大小
#define PRODUCT_CNT 50 //产品生产总数
struct product_cons
{
int buffer[BUFFER_SIZE]; //生产产品值
pthread_mutex_t lock; //互斥锁 volatile int
int readpos, writepos; //读写位置
pthread_cond_t notempty; //条件变量，非空
pthread_cond_t notfull; //非满
pthread_mutex_t lock2; //互斥锁，控制cnt_p
int cnt_p; //完成生产产品数量
pthread_mutex_t lock3; //互斥锁，控制cnt_c
int cnt_c; //获得生产产品数量
}buffer;
void init(struct product_cons *p)
{
pthread_mutex_init(&p->lock, NULL); //互斥锁
pthread_cond_init(&p->notempty, NULL); //条件变量
pthread_cond_init(&p->notfull, NULL); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_init(&p->lock2, NULL);
p->cnt_p = 0;
pthread_mutex_init(&p->lock3, NULL);
p->cnt_c = 0;
}
void fini(struct product_cons *p)
{
pthread_mutex_destroy(&p->lock); //互斥锁
pthread_cond_destroy(&p->notempty); //条件变量
pthread_cond_destroy(&p->notfull); //条件变量
p->readpos = 0; //读写位置
p->writepos = 0;
pthread_mutex_destroy(&p->lock2);
p->cnt_p = 0;
pthread_mutex_destroy(&p->lock3);
p->cnt_c = 0;
}
//存储 一个数据 到 bufferr
void put(struct product_cons *p, int data) //输入产品子函数
{
pthread_mutex_lock(&p->lock); //上锁
/*等待，直到 buffer 不为 满*/
while((p->writepos + 1) % BUFFER_SIZE == p->readpos) //测试空间是否已满
{
printf("producer wait for not full\n");
pthread_cond_wait(&p->notfull, &p->lock); //阻塞等待
//这里，生产者 notfull 等待消费者 pthread_cond_signal(&p->notfull);信号
//如果，消费者发送了 signal 信号，表示有了 空闲
}
p->buffer[p->writepos] = data; //写数据
p->writepos++;
if(p->writepos >= BUFFER_SIZE) //如果写到 尾部,返回
p->writepos = 0;
pthread_cond_signal(&p->notempty); //发送有数据信号
pthread_mutex_unlock(&p->lock); //解锁
}
//读，移除 一个数据 从 buffer
int get(struct product_cons *p)
{
int data = 0;
pthread_mutex_lock(&p->lock);
/*等待，直到不为空*/
while(p->writepos == p->readpos)
{
printf("consumer wait for not empty\n");
pthread_cond_wait(&p->notempty,&p->lock);
}
/*读 一个 数据*/
data = p->buffer[p->readpos];
p->readpos++;
if(p->readpos >= BUFFER_SIZE) //如果读到 尾
p->readpos = 0;
pthread_cond_signal(&p->notfull);
pthread_mutex_unlock(&p->lock);
return data;
}
void *producer(void *data) //子线程 ，生产
{
int flag = -1;
while(1)
{
pthread_mutex_lock(&buffer.lock2);
if(buffer.cnt_p < PRODUCT_CNT)
{
++buffer.cnt_p;
printf("%s put the %d product\n", (char*)data, buffer.cnt_p);
put(&buffer, buffer.cnt_p);
}
else
flag = 0;
pthread_mutex_unlock(&buffer.lock2);
if(!flag)
break;
sleep(2);
}
printf("%s producer stopped\n", (char*)data);
return NULL;
}
void *consumer(void *data)
{
int flag = -1;
while(1)
{
pthread_mutex_lock(&buffer.lock3);
if(buffer.cnt_c < PRODUCT_CNT)
{
printf("%s get the %d product\n", (char*)data, get(&buffer));
++buffer.cnt_c;
}
else
flag = 0;
pthread_mutex_unlock(&buffer.lock3);
if(!flag)
break;
sleep(2);
}
printf("%s consumer stopped\n", (char*)data);
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t th_a[3],th_b[3];
void *retval;
init(&buffer);
pthread_create(&th_a[0], NULL, producer, (void*)"th_a[0]");
pthread_create(&th_a[1], NULL, producer, (void*)"th_a[1]");
pthread_create(&th_a[2], NULL, producer, (void*)"th_a[2]");
pthread_create(&th_b[0], NULL, consumer, (void*)"th_b[0]");
pthread_create(&th_b[1], NULL, consumer, (void*)"th_b[1]");
pthread_create(&th_b[2], NULL, consumer, (void*)"th_b[2]");
pthread_join(th_a[0], &retval);
pthread_join(th_a[1], &retval);
pthread_join(th_a[2], &retval);
pthread_join(th_b[0], &retval);
pthread_join(th_b[1], &retval);
pthread_join(th_b[2], &retval);
fini(&buffer);
return 0;
}