線程同步

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同步主線程與子線程

test.c #include <pthread.h> #include <sys/syscall.h> #include <fcntl.h> #include <semaphore.h> #include <stdlib.h> #include <stdio.h>void* ret_result_thread1; sem_t *sem;void* thread1Func(void* arg) {printf("childThread id:%u is running\n", syscall(SYS_gettid));sleep(2);sem_post(sem);pthread_exit((void*)0);}int main(int argc, char** argv) {printf("main thread start\n");const char* semName="sem_name";sem = sem_open(semName,O_CREAT,0644,0);pthread_t thread1;int ret1;if( (ret1 = pthread_create(&thread1,NULL,thread1Func,NULL)) != 0){perror("thread1 create failed");}sem_wait(sem);printf("main thread end\n");pthread_join(thread1,ret_result_thread1);sem_close(sem);sem_unlink(semName); return 0; }

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子線程之間的同步

使用單個信號量

#include <pthread.h> #include <sys/syscall.h> #include <fcntl.h> #include <semaphore.h> #include <stdlib.h> #include <stdio.h>void* ret_result_thread1; void* ret_result_thread2; sem_t *sem;void* thread1Func(void* arg) {printf("childThread1 is running\n");sleep(2);sem_post(sem);pthread_exit((void*)0); }void* thread2Func(void* arg) {sem_wait(sem);printf("childThread2 is running\n"); sleep(2);pthread_exit((void*)0); }int main(int argc, char** argv) {printf("main thread start\n");const char* semName="sem_name";sem = sem_open(semName,O_CREAT,0644,0);pthread_t thread1,thread2;int ret1;int ret2;if( (ret1 = pthread_create(&thread1,NULL,thread1Func,NULL)) != 0){perror("thread1 create failed");}if( (ret2 = pthread_create(&thread2,NULL,thread2Func,NULL)) != 0){perror("thread2 create failed");}printf("main thread end\n");pthread_join(thread1,ret_result_thread1);pthread_join(thread2,ret_result_thread2); sem_close(sem);sem_unlink(semName); return 0; }

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使用兩個信號量

test.c #include <pthread.h> #include <sys/syscall.h> #include <fcntl.h> #include <semaphore.h> #include <stdlib.h> #include <stdio.h>void* ret_result_thread1; void* ret_result_thread2; sem_t *sem1; sem_t *sem2;void* thread1Func(void* arg) {sem_wait(sem1);printf("childThread1 is running\n");sleep(2);sem_post(sem2);pthread_exit((void*)0);}void* thread2Func(void* arg) {sem_wait(sem2);printf("childThread2 is running\n"); sleep(2);sem_post(sem1);pthread_exit((void*)0); }int main(int argc, char** argv) {printf("main thread start\n");const char* semName1="sem_name1";sem1 = sem_open(semName1,O_CREAT,0644,1);const char* semName2="sem_name2";sem2 = sem_open(semName2,O_CREAT,0644,0);pthread_t thread1,thread2;int ret1;int ret2;if( (ret1 = pthread_create(&thread1,NULL,thread1Func,NULL)) != 0){perror("thread1 create failed");}if( (ret2 = pthread_create(&thread2,NULL,thread2Func,NULL)) != 0){perror("thread2 create failed");}printf("main thread end\n");pthread_join(thread1,ret_result_thread1);pthread_join(thread2,ret_result_thread2); sem_close(sem1);sem_close(sem2);sem_unlink(semName1);sem_unlink(semName2); return 0; }

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主線程運行結束后，線程1開始運行，休眠2秒后開始運行線程2

總結

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