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pthread_cleanup_push()

Push a function onto a thread's cancellation-cleanup stack

Synopsis:

#include <pthread.h>

void pthread_cleanup_push( void (routine)(void*),
                           void* arg );

Arguments:

routine

The handler that you want to push onto the thread's stack.

arg

A pointer to whatever data you want to pass to the function when it's called.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pthread_cleanup_push() function pushes the given cancellation-cleanup handler routine onto the calling thread's cancellation-cleanup stack.

The cancellation-cleanup handler is popped from the stack and invoked with argument arg when the thread:

• exits (i.e. calls pthread_exit())
• acts on a cancellation request
• calls pthread_cleanup_pop() with a nonzero argument.

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The pthread_cleanup_push() macro expands to a few lines of code that start with an opening brace ({), but don't have a matching closing brace (}). You must pair pthread_cleanup_push() with pthread_cleanup_pop() within the same lexical scope.

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Examples:

Use a cancellation cleanup handler to free resources, such as a mutex, when a thread is terminated:

#include <pthread.h>

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

void unlock( void * arg )
{
   pthread_mutex_unlock( &lock );
}

void * function( void * arg )
{
   while( 1 )
   {
      pthread_mutex_lock( &lock );
      pthread_cleanup_push( &unlock, NULL );

      /*
       Any of the possible cancellation points could
       go here.
      */
      pthread_testcancel();

      pthread_cleanup_pop( 1 );
   }
}

Classification:

POSIX 1003.1 THR

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

See also:

pthread_cleanup_pop(), pthread_cancel(), pthread_exit()

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