Linux programming--Canceling a thread (12th chapter)

Source: Internet
Author: User

12.7 canceling a thread sometimes, you want a thread to require another thread to terminate, just like sending a signal to it. Threads have methods that can do this, as with signal processing, where a thread can be asked to change its behavior when terminated.
Pthread_cancel is a function for requesting a thread to terminate
#inlude <pthread.h>int pthread_cancel (pthread_t thread);
This function provides a thread identifier to send a request to cancel it.
Threads can be used pthread_setcancelstate Setting the cancellation state of a thread
#include <pthread.h>int pthread_setcancelstate (int state, int *oldstate);
The value of the first parameter can be pthread_cancel_enable, which allows the thread to receive a cancellation request, or pthread_cancel_disable, which is the function of ignoring the cancellation request. The oldstate pointer is used to get the previous cancellation state.
If the cancellation request is accepted, the thread can enter a second control level, using the Pthread_setcanceltype Setting the cancellation type
#include <pthread.h>int pthread_setcanceltype (int type, int *oldtype);
The type parameter can have two values: one is pthread_cancel_asynchronour, it will take action immediately after the cancellation request is received, and the other is pthread_cancel_deferred, which will make it possible to accept the cancellation request Wait until the thread executes one of the following functions before taking action. Specifically, the function pthread_join,pthread_cond_wait,pthread_cond_timedwait,pthread_testcancel,sem_wait or sigwait.
Writing the program thread7.c, the main thread sends a cancellation request to the threads it creates.
/************************************************************************* > File name:thread7.c > The DESCRIPTION:THREAD7.C program sends a cancel request to the new thread it creates in the main thread > author:liubingbing > Created time:2015/7/7 9:58:40 > Oth The new thread's calling function in the ER:THREAD7.C program needs to set the cancellation state and the type of cancellation for each thread ******************************************************************* /#include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <pthread.h>void * Thread_function (void *arg); int main () {int res;pthread_t a_thread;void *thread_result;/* pthread_create function creates a new thread, The new thread identifier is saved in A_thread, the function called by the new thread is thread_function, the function parameter is NULL */res = pthread_create (&a_thread, NULL, Thread_function, NULL); if (res! = 0) {perror ("Thread creation failed"); exit (exit_failure);} Sleep (3);p rintf ("canceling thread...\n");/* Pthread_cancel function Request Thread a_thread Terminate */res = Pthread_cancel (A_thread); if (res!) = 0) {perror ("Thread cancelation failed"); exit (exit_failure);} printf ("Waiting for Thread to finish...\n");/* Pthread_join waitThe thread a_thread is re-merged with the main thread */res = Pthread_join (A_thread, &thread_result), if (res! = 0) {perror ("thread join Failed"); exit ( Exit_failure);} Exit (exit_success);} void *thread_function (void *arg) {int I, res;/* pthread_setcancelstate function sets the cancellation state of the thread, Pthread_cancel_enable allows the thread to receive the cancellation request Pthread_cancel_disable ignores cancellation Request */res = Pthread_setcancelstate (pthread_cancel_enable, NULL); if (res! = 0) {perror (" Thread pthread_setcancelstate failed "); exit (exit_failure);} /* Pthread_setcanceltype function sets the type of cancellation for the thread, pthread_cancel_deferred will cause the cancellation request to wait until the thread executes a function, such as Pthread_join, before taking action. res = Pthread_setcanceltype (pthread_cancel_deferred, NULL), if (res! = 0) {perror ("Thread Pthread_setcanceltype failed") ; exit (exit_failure);} printf ("Thread_function is running\n"); for (i = 0; i <; i++) {printf ("thread is still running (%d) ... \ n", i); sleep (1) ;} Pthread_exit (0);}
After creating a new thread in the usual way, the main thread sleeps for a while (so that the new thread has time to start executing), and then sends a cancellation request as follows:
Sleep (3);p rintf ("canceling thread...\n"); res = Pthread_cancel (a_thread);
In the newly created thread, first set the cancellation status to allow cancellation, as follows:
res = Pthread_setcancelstate (pthread_cancel_enable, NULL);
Then set the cancellation type to deferred cancellation, as follows:
res = Pthread_setcanceltype (pthread_cancel_deferred, NULL);
Finally, the thread waits in the loop to be canceled, as follows:
for (i = 0; i < i++) {    printf ("Thread is still running (%d) ... \ n", i);    Sleep (1);}

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Linux programming--Canceling a thread (12th chapter)

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