pthread_testcancel()--Create Cancellation Point
Syntax
#include <pthread.h>
void pthread_testcancel(void);
Threadsafe: Yes
Signal 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);
-
- sleep(2);
- while (1) {
- printf("Secondary thread is now looping/n");
- ++i;
- sleep(1);
-
-
-
- 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);
-
-
- }
- }
- 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]);
-
-
- 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/TPTESTC0
- Create thread using the NULL attributes
- Entered secondary thread
- Cancel the thread
- Secondary thread is now looping
- Secondary thread is now looping
- Secondary thread is now looping
- Secondary thread is now looping
- Secondary thread is now looping
- Cancel state set to ENABLE
- Secondary thread is now looping
- Inside cancellation cleanup handler
- Main completed
