How to synchronize threads among multiple processes using mutexes allocated by XSI IPC shared memory
This article mainly introduces how to use XSI IPC shared memory allocation mutex to synchronize the threads between multiple processes in Camp Candle +. It has a certain reference value, and interested friends can refer to it. I hope you can learn a lot after reading this article. Let's take a look at it.
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# define handle_error_en (en, msg)\
Do {errno = en; perror (msg); exit (EXIT_FAILURE);} while (0)
Static pthread_mutex_t * mtx
Static void * original_owner_thread (void * ptr) {
Printf ("[original owner] Setting lock...\ n")
Pthread_mutex_lock (mtx)
Printf ("[original owner] Locked. Now exiting without unlocking.\ n")
Pthread_exit (NULL); / / exit after lock addition does not release lock
}
Int main () {
Pid_t pid_robust
Int shmid
/ / use XSI IPC to allocate mutex memory
Shmid = shmget (IPC_PRIVATE,sizeof (pthread_mutex_t), IPC_CREAT | IPC_EXCL)
/ / get memory area pointer
Mtx=shmat (shmid,0,0)
Pid_robust = fork ()
Int proc_status
Int ret
If (pid_robust 0) {
Pthread_t thr_p
Pthread_mutexattr_t attr
Pthread_mutexattr_init & attr)
Pthread_mutexattr_setpshared & attr,PTHREAD_PROCESS_SHARED)
Pthread_mutexattr_setrobust (& attr, PTHREAD_MUTEX_ROBUST)
Pthread_mutex_init (mtx, & attr)
Pthread_create (& thr_p, NULL, original_owner_thread, NULL)
} else if (0==pid_robust) {
Int err_code
Sleep (2)
Printf ("[fork main thread] Attempting to lock the robust mutex.\ n")
Err_code = pthread_mutex_lock (mtx)
If (err_code = = EOWNERDEAD) {
Printf ("[fork main thread] pthread_mutex_lock () returned EOWNERDEAD\ n")
Printf ("[fork main thread] Now make the mutex consistent\ n")
Err_code = pthread_mutex_consistent (mtx); / / call the function to change the owner of the lock, that is, the lock is changed from the previous owner to the host thread
If (err_code! = 0) {
Handle_error_en (err_code, "pthread_mutex_consistent")
}
Printf ("[fork main thread] Mutex is now consistent; unlocking\ n")
Err_code = pthread_mutex_unlock (mtx)
If (err_code = = 0) {
Printf ("[fork main thread] pthread_mutex_lock () unexpectedly succeeded\ n")
} else {
Handle_error_en (err_code, "pthread_mutex_unlock")
}
} else {
Printf ("[fork main thread] lock success!% d\ n", err_code)
}
Exit (0)
}
Printf ("parent main thread waiting fork process\ n")
Sleep (2)
If (waitpid (pid_robust,&proc_status,0) < 0) {
Printf ("[parent main thread] waiting for fork process error.\ n")
Return 127
}
If (WIFEXITED (proc_status)) {
Return 0
}
Return 127
}
Compile:
Gcc-lpthread-o muti_proc_thread_lock muti_proc_thread_lock.c
Results:
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