使用 pthread_testcancel 作为pthread_cancel 时 线程的退出点函数

 

pthread_testcancel()--Create Cancellation Point

Syntax 

#include <pthread.h>void pthread_testcancel(void);Threadsafe: YesSignal Safe: No

The pthread_testcancel() function creates a cancellation point in the calling thread. If cancelability is currently disabled, this function has no effect. For more information on cancelability, see Thread cancellation APIs.

When cancelability is disabled, all cancels are held pending in the target thread until the thread changes the cancelability. When cancelability is deferred, all cancels are held pending in the target thread until the thread changes the cancelability, calls a function that is a cancellation point, or calls pthread_testcancel(), thus creating a cancellation point. When cancelability is asynchronous, all cancels are acted upon immediately, interrupting the thread with its processing.

You should not use asynchronous thread cancellation via the PTHREAD_CANCEL_ASYNCHRONOUS option of pthread_setcanceltype(). See the common user errors section of this document for more information.

 

#define _MULTI_THREADED#include <pthread.h>#include <stdio.h>#include "check.h"void cleanupHandler(void *parm) { printf("Inside cancellation cleanup handler/n");}void *threadfunc(void *parm){ unsigned int i=0; int rc=0, oldState=0; printf("Entered secondary thread/n"); pthread_cleanup_push(cleanupHandler, NULL); rc = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldState); checkResults("pthread_setcancelstate()/n", rc); /* Allow cancel to be pending on this thread */ sleep(2); while (1) { printf("Secondary thread is now looping/n"); ++i; sleep(1); /* pthread_testcancel() has no effect until cancelability is enabled.*/ /* At that time, a call to pthread_testcancel() should result in the */ /* pending cancel being acted upon */ pthread_testcancel(); if (i == 5) { printf("Cancel state set to ENABLE/n"); rc = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE,&oldState); checkResults("pthread_setcancelstate(2)/n", rc); /* Now, cancellation points will allow pending cancels to get through to this thread */ } } /* infinite */ pthread_cleanup_pop(0); return NULL;}int main(int argc, char **argv){ pthread_t thread; int rc=0; void *status=NULL; printf("Enter Testcase - %s/n", argv[0]); /* Create a thread using default attributes */ printf("Create thread using the NULL attributes/n"); rc = pthread_create(&thread, NULL, threadfunc, NULL); checkResults("pthread_create(NULL)/n", rc); sleep(1); printf("Cancel the thread/n"); rc = pthread_cancel(thread); checkResults("pthread_cancel()/n", rc); rc = pthread_join(thread, &status); if (status != PTHREAD_CANCELED) { printf("Thread returned unexpected result!/n"); exit(1); } printf("Main completed/n"); return 0;}Output:Enter Testcase - QP0WTEST/TPTESTC0Create thread using the NULL attributesEntered secondary threadCancel the threadSecondary thread is now loopingSecondary thread is now loopingSecondary thread is now loopingSecondary thread is now loopingSecondary thread is now loopingCancel state set to ENABLESecondary thread is now loopingInside cancellation cleanup handlerMain completed