将互斥锁属性的类型设置为PTHREAD_MUTEX_RECURSIVE

如果将互斥锁属性的类型设置为PTHREAD_MUTEX_RECURSIVE，则同一个线程可以多次进入临界区

程序如下

#include <pthread.h>#include <stdio.h>#include <string.h>#include <stdlib.h>pthread_mutex_t mutex; pthread_mutexattr_t attr; void* func(void* arg){if(*(char*)arg == '\0') return NULL;pthread_mutex_lock(&mutex);char* str = (char*)arg;while(*str != '\0'){fputc(*str, stdout);str++;}fputc('\n', stdout);func((char*)arg+1);pthread_mutex_unlock(&mutex);return NULL;}int main(){int ret;if(( ret = pthread_mutexattr_init(&attr)) != 0){fprintf(stderr, "create mutex attribute error. msg:%s", strerror(ret));exit(1);}pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);pthread_mutex_init(&mutex, &attr);pthread_t p1, p2; char str1[8], str2[8]; sprintf(str1, "abcdefg");sprintf(str2, "1234567");if((ret = pthread_create(&p1, NULL, func, str1)) != 0){fprintf(stderr, "create thread error. msg:%s", strerror(ret));exit(1);}if((ret = pthread_create(&p2, NULL, func, str2)) != 0){fprintf(stderr, "create thread error. msg:%s", strerror(ret));exit(1);}pthread_join(p1, NULL);pthread_join(p2, NULL);}

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