threads/thread_cleanup.c

This is threads/thread_cleanup.c (Listing 32-2, page 678), an example from the book, The Linux Programming Interface.

The source code file is copyright 2024, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

This page shows the "distribution" or "book" version of the file (why are there two versions?), or the differences between the two versions. You can switch between the views using the tabs below.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.

 

Download threads/thread_cleanup.c

  Cover of The Linux Programming Interface

Function list (Bold in this list means a function is not static)

#include <pthread.h>
#include "tlpi_hdr.h"

static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
static int glob = 0;                    /* Predicate variable */
static void     /* Free memory pointed to by 'arg' and unlock mutex */
cleanupHandler(void *arg)
{
    int s;

    printf("cleanup: freeing block at %p\n", arg);
    free(arg);

    printf("cleanup: unlocking mutex\n");
    s = pthread_mutex_unlock(&mtx);
    if (s != 0)
        errExitEN(s, "pthread_mutex_unlock");
}
static void *
threadFunc(void *arg)
{
    int s;
    void *buf = NULL;                   /* Buffer allocated by thread */

    buf = malloc(0x10000);              /* Not a cancellation point */
    printf("thread:  allocated memory at %p\n", buf);

    s = pthread_mutex_lock(&mtx);       /* Not a cancellation point */
    if (s != 0)
        errExitEN(s, "pthread_mutex_lock");

    pthread_cleanup_push(cleanupHandler, buf);

    while (glob == 0) {
        s = pthread_cond_wait(&cond, &mtx);     /* A cancellation point */
        if (s != 0)
            errExitEN(s, "pthread_cond_wait");
    }

    printf("thread:  condition wait loop completed\n");
    pthread_cleanup_pop(1);             /* Executes cleanup handler */
    return NULL;
}
int
main(int argc, char *argv[])
{
    pthread_t thr;
    void *res;
    int s;

    s = pthread_create(&thr, NULL, threadFunc, NULL);
    if (s != 0)
        errExitEN(s, "pthread_create");

    sleep(2);                   /* Give thread a chance to get started */

    if (argc == 1) {            /* Cancel thread */
        printf("main:    about to cancel thread\n");
        s = pthread_cancel(thr);
        if (s != 0)
            errExitEN(s, "pthread_cancel");

    } else {                    /* Signal condition variable */
        printf("main:    about to signal condition variable\n");
        glob = 1;
        s = pthread_cond_signal(&cond);
        if (s != 0)
            errExitEN(s, "pthread_cond_signal");
    }

    s = pthread_join(thr, &res);
    if (s != 0)
        errExitEN(s, "pthread_join");
    if (res == PTHREAD_CANCELED)
        printf("main:    thread was canceled\n");
    else
        printf("main:    thread terminated normally\n");

    exit(EXIT_SUCCESS);
}

 

Download threads/thread_cleanup.c

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

Valid XHTML 1.1