cancel_subcontract.c

/*
 * cancel_subcontract.c
 *
 * Demonstrate how a thread can handle cancellation and in turn
 * cancel a set of worker ("subcontractor") threads.
 *
 * Special notes: On a Solaris 2.5 uniprocessor, this test will
 * hang unless an LWP is created for each worker thread by
 * calling thr_setconcurrency(), because threads are not
 * timesliced.
 */
#include <pthread.h>
#include "errors.h"

#define THREADS 5

/*
 * Structure that defines the threads in a "team".
 */
typedef struct team_tag {
   int          join_i;                 /* join index */
   pthread_t    workers[THREADS];       /* thread identifiers */
} team_t;

/*
 * Start routine for worker threads. They loop waiting for a
 * cancellation request.
 */
void *worker_routine (void *arg)
{
    int counter;

    for (counter = 0; ; counter++)
        if ((counter % 1000) == 0)
            pthread_testcancel ();
}

/*
 * Cancellation cleanup handler for the contractor thread. It
 * will cancel and detach each worker in the team.
 */
void cleanup (void *arg)
{
    team_t *team = (team_t *)arg;
    int count, status;

    for (count = team->join_i; count < THREADS; count++) {
        status = pthread_cancel (team->workers[count]);
        if (status != 0)
            err_abort (status, "Cancel worker");

        status = pthread_detach (team->workers[count]);
        if (status != 0)
            err_abort (status, "Detach worker");
        printf ("Cleanup: cancelled %d\n", count);
    }
}

/*
 * Thread start routine for the contractor. It creates a team of
 * worker threads, and then joins with them. When cancelled, the
 * cleanup handler will cancel and detach the remaining threads.
 */
void *thread_routine (void *arg)
{
    team_t team;                        /* team info */
    int count;
    void *result;                       /* Return status */
    int status;

    for (count = 0; count < THREADS; count++) {
        status = pthread_create (
            &team.workers[count], NULL, worker_routine, NULL);
        if (status != 0)
            err_abort (status, "Create worker");
    }
    pthread_cleanup_push (cleanup, (void*)&team);

    for (team.join_i = 0; team.join_i < THREADS; team.join_i++) {
        status = pthread_join (team.workers[team.join_i], &result);
        if (status != 0)
            err_abort (status, "Join worker");
    }

    pthread_cleanup_pop (0);
    return NULL;
}

int main (int argc, char *argv[])
{
    pthread_t thread_id;
    int status;

#ifdef sun
    /*
     * On Solaris 2.5, threads are not timesliced. To ensure
     * that our threads can run concurrently, we need to
     * increase the concurrency level to at least 2 plus THREADS
     * (the number of workers).
     */
    DPRINTF (("Setting concurrency level to %d\n", THREADS+2));
    thr_setconcurrency (THREADS+2);
#endif
    status = pthread_create (&thread_id, NULL, thread_routine, NULL);
    if (status != 0)
        err_abort (status, "Create team");
    sleep (5);
    printf ("Cancelling...\n");
    status = pthread_cancel (thread_id);
    if (status != 0)
        err_abort (status, "Cancel team");
    status = pthread_join (thread_id, NULL);
    if (status != 0)
        err_abort (status, "Join team");
    return 0;
}