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Linux编程练习 --多线程3--mutex
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互斥指互相排斥的鎖，是一種信號(hào)量，常用來防止兩個(gè)進(jìn)程或線程在同一時(shí)刻訪問相同的共享資源
????????
1.數(shù)據(jù)類型：
?在Linux下,?線程的互斥量數(shù)據(jù)類型是pthread_mutex_t，我們定義一個(gè)互斥數(shù)據(jù)可以這樣：
????????????? pthread_mutex_t mutex;
?
2.函數(shù)說明：
頭文件：?????pthread.h
（1）.互斥鎖初始化：
?
函數(shù)原型：?int pthread_mutex_init (pthread_mutex_t* mutex,
?????????????????????????????????const pthread_mutexattr_t*???mutexattr);
函數(shù)傳入值:? mutex:互斥鎖。
????????????????mutexattr:PTHREAD_MUTEX_INITIALIZER:創(chuàng)建快速互斥鎖。
????????????????PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP:創(chuàng)建遞歸互斥鎖。
???????????????????PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP:創(chuàng)建檢錯(cuò)互斥鎖。
函數(shù)返回值：?成功：0
???????????????????出錯(cuò)：-1?
（2）.互斥操作函數(shù)
int pthread_mutex_lock(pthread_mutex_t* mutex);//上鎖
int pthread_mutex_trylock (pthread_mutex_t* mutex);//只有在互斥被鎖住的情況下才阻塞
int pthread_mutex_unlock (pthread_mutex_t* mutex);//解鎖
int pthread_mutex_destroy (pthread_mutex_t* mutex);//清除互斥鎖
函數(shù)傳入值：??????????? mutex:互斥鎖。
函數(shù)返回值：???????????成功：0
????????????????????????????? 出錯(cuò)：-1
3.使用形式：
struct mutex mutex;
mutex_init(&mutex); /*定義*/
...
mutex_lock(&mutex); /*獲取互斥鎖*/
... /*臨界資源*/
mutex_unlock(&mutex); /*釋放互斥鎖*/
?
?
最后進(jìn)行一個(gè)練習(xí)：我們創(chuàng)建兩個(gè)線程，分別訪問全局變量gnum，并且修改它，打印出來
[cpp]?view plaincopy
/*mutex.c*/??#include?<stdlib.h>????#include?<stdio.h>????#include?<pthread.h>????#include?<errno.h>?????/*全局變量*/??int?gnum?=?0;??/*互斥量?*/??pthread_mutex_t?mutex;??/*聲明線程運(yùn)行服務(wù)程序*/??static?void?pthread_func_1?(void);?????static?void?pthread_func_2?(void);?????????int?main?(void)?????{??????/*線程的標(biāo)識(shí)符*/????pthread_t?pt_1?=?0;???????pthread_t?pt_2?=?0;???????int?ret?=?0;???????/*互斥初始化*/????pthread_mutex_init?(&mutex,?NULL);?????/*分別創(chuàng)建線程1、2*/????ret?=?pthread_create?(&pt_1,??????????//線程標(biāo)識(shí)符指針???????????????????????????NULL,??????????//默認(rèn)屬性??????????????????????????(void?*)pthread_func_1,//運(yùn)行函數(shù)??????????????????????????NULL);??????????//無參數(shù)????if?(ret?!=?0)???????{??????????perror?("pthread_1_create");???????}???????????ret?=?pthread_create?(&pt_2,??????????//線程標(biāo)識(shí)符指針??????????????????????????NULL,???????????//默認(rèn)屬性????????????????????????????(void?*)pthread_func_2,?//運(yùn)行函數(shù)??????????????????????????NULL);??????????//無參數(shù)????if?(ret?!=?0)???????{??????????perror?("pthread_2_create");???????}???????/*等待線程1、2的結(jié)束*/????pthread_join?(pt_1,?NULL);???????pthread_join?(pt_2,?NULL);???????????printf?("main?programme?exit!/n");??????return?0;?????}?????/*線程1的服務(wù)程序*/??static?void?pthread_func_1?(void)?????{???????int?i?=?0;??????????????for?(;;)???????{?????????printf?("This?is?pthread1!/n");??????????pthread_mutex_lock(&mutex);?/*獲取互斥鎖*/??????/*注意，這里以防線程的搶占，以造成一個(gè)線程在另一個(gè)線程sleep時(shí)多次訪問互斥資源，所以sleep要在得到互斥鎖后調(diào)用*/??????sleep?(1);????????/*臨界資源*/??????gnum++;??????printf?("Thread1?add?one?to?num:%d/n",gnum);??????pthread_mutex_unlock(&mutex);?/*釋放互斥鎖*/?????????????}?????}?????/*線程2的服務(wù)程序*/???static?void?pthread_func_2?(void)?????{???????int?i?=?0;???????????for?(;;)???????{?????????printf?("This?is?pthread2!/n");???????pthread_mutex_lock(&mutex);?/*獲取互斥鎖*/??????/*注意，這里以防線程的搶占，以造成一個(gè)線程在另一個(gè)線程sleep時(shí)多次訪問互斥資源，所以sleep要在得到互斥鎖后調(diào)用*/??????sleep?(1);??????/*臨界資源*/??????gnum++;??????printf?("Thread2?add?one?to?num:%d/n",gnum);??????pthread_mutex_unlock(&mutex);?/*釋放互斥鎖*/????????}???????????pthread_exit?(0);?????}????
然后編譯，運(yùn)行，看到是線程1，2分別和平地訪問共享資源
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