/*      $OpenBSD: blocked_fifo.c,v 1.2 2012/07/08 11:35:37 guenther Exp $       */
/*
 * Copyright (c) 2012 Owain G. Ainsworth <oga@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Test fifo opening blocking the file descriptor table and thus all other
 * opens in the process.
 * Symptoms are that the main thread will sleep on fifor (in the fifo open) and
 * the deadlocker on fdlock (in open of any other file).
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <pthread.h>
#include <unistd.h>
#include <fcntl.h>
#include "test.h"

#define FIFO    "pthread.fifo"
#define FILE    "/etc/services" /* just any file to deadlock on */

int     free_fd, expected_fd;

static void *
deadlock_detector(void *arg)
{
        sleep(10);
        unlink(FIFO);
        PANIC("deadlock detected");
}

static void *
fifo_deadlocker(void *arg)
{
        int     fd;

        /* let other fifo open start */
        sleep(3);

        /* open a random temporary file, if we don't deadlock this'll succeed */
        CHECKe(fd = open(FILE, O_RDONLY));
        CHECKe(close(fd));

        /* open fifo to unblock other thread */
        CHECKe(fd = open(FIFO, O_WRONLY));
        CHECKe(write(fd, "test", 4));
        CHECKe(close(fd));

        return ((caddr_t)NULL + errno);
}

static void *
fifo_closer(void *arg)
{
        int     fd;

        /* let other fifo open start */
        sleep(3);

        /* open a random temporary file and dup2 it over the FIFO */
        CHECKe(fd = open(FILE, O_RDONLY));
        CHECKe(dup2(fd, expected_fd));
        CHECKe(close(fd));
        CHECKe(close(expected_fd));

        /* open fifo to unblock other thread */
        CHECKe(fd = open(FIFO, O_WRONLY));
        CHECKe(write(fd, "test", 4));
        CHECKe(close(fd));

        return ((caddr_t)NULL + errno);
}

int
main(int argc, char *argv[])
{
        pthread_t        test_thread, deadlock_finder;
        struct stat      st;
        char             buf[5];
        int              fd;
        ssize_t          rlen;

        unlink(FIFO);
        CHECKe(mkfifo(FIFO, S_IRUSR | S_IWUSR));

        CHECKr(pthread_create(&deadlock_finder, NULL,
            deadlock_detector, NULL));

        /*
         * Verify that other threads can still do fd-table operations
         * while a thread is blocked opening a FIFO
         */
        CHECKr(pthread_create(&test_thread, NULL, fifo_deadlocker, NULL));

        /* Open fifo (this will sleep until we have readers) */
        CHECKe(fd = open(FIFO, O_RDONLY));

        CHECKe(fstat(fd, &st));
        ASSERT(S_ISFIFO(st.st_mode));
        CHECKe(rlen = read(fd, buf, sizeof buf));
        ASSERT(rlen == 4);

        CHECKr(pthread_join(test_thread, NULL));

        CHECKe(close(fd));


        /*
         * Verify that if a thread is blocked opening a FIFO and another
         * thread targets the half-open fd with dup2 that it doesn't blow up.
         */
        CHECKr(pthread_create(&test_thread, NULL, fifo_closer, NULL));

        free_fd = open("/dev/null", O_RDONLY);
        expected_fd = dup(free_fd);
        close(expected_fd);

        /* Open fifo (this will sleep until we have readers) */
        CHECKe(fd = open(FIFO, O_RDONLY));

        ASSERT(fd == expected_fd);
        ASSERT(close(fd) == -1);
        ASSERT(errno == EBADF);

        CHECKr(pthread_join(test_thread, NULL));

        CHECKe(close(free_fd));


        /* clean up */
        unlink(FIFO);

        SUCCEED;
}