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/*-

 * Copyright (c) 2005, Kohsuke Ohtani

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the author nor the names of any co-contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

/*

 * deadlock.c - test program for a kernel deadlock detection.

 */

/*

 * Prex kernel has the feature of deadlock detection. The following

 * senario is tested with this program.

 *

 * 1) Thread-2 locks mutex-A.

 * 2) Thread-1 locks mutex-B.

 * 3) Thread-1 locks mutex-A.

 * 4) Thread-2 locks mutex-B.

 *

 * The deadlock occurs at 4) because mutex-B has been already locked by

 * thread-1 and thread-1 is waiting for thread-2 (mutex-A).

 * The kernel will detect this condition, and the mutex_lock() system

 * call will return EDEADLK error code.

 */

#include <sys/prex.h>

#include <stdio.h>

#include <errno.h>

static char stack[2][1024];

static thread_t th_1, th_2;

static mutex_t mtx_A, mtx_B;

thread_t

thread_run(void (*start)(void), void *stack)

{

        thread_t t;

        int error;

        error = thread_create(task_self(), &t);

        if (error)

                panic("thread_create is failed");

        error = thread_load(t, start, stack);

        if (error)

                panic("thread_load is failed");

        return t;

}

/*

 * Thread 1 - Priority = 100

 */

static void

thread_1(void)

{

        int error;

        printf("thread_1: starting\n");

        /*

         * 2) Lock mutex B

         */

        printf("thread_1: 2) lock B\n");

        error = mutex_lock(&mtx_B);

        if (error) printf("error=%d\n", error);

        /*

         * 3) Lock mutex A

         *

         * Switch to thread 1.

         */

        printf("thread_1: 3) lock A\n");

        error = mutex_lock(&mtx_A);

        if (error) printf("error=%d\n", error);

        printf("thread_1: exit\n");

        thread_terminate(th_1);

}

/*

 * Thread 2 - Priority = 101

 */

static void

thread_2(void)

{

        int error;

        printf("thread_2: starting\n");

        /*

         * 1) Lock mutex A

         */

        printf("thread_2: 1) lock A\n");

        error = mutex_lock(&mtx_A);

        if (error) printf("error=%d\n", error);

        /*

         * Switch to thread 1

         */

        thread_resume(th_1);

        printf("thread_2: running\n");

        /*

         * 4) Lock mutex B

         *

         * Deadlock occurs here!

         */

        printf("thread_2: 4) lock B\n");

        error = mutex_lock(&mtx_B);

        if (error) printf("error=%d\n", error);

        if (error == EDEADLK)

                printf("**** DEADLOCK!! ****\n");

        printf("thread_2: exit\n");

        thread_terminate(th_2);

}

int

main(int argc, char *argv[])

{

        printf("Deadlock test program\n");

        /*

         * Boost priority of this thread

         */

        thread_setpri(thread_self(), 90);

        /*

         * Initialize mutexes.

         */

        mutex_init(&mtx_A);

        mutex_init(&mtx_B);

        /*

         * Create new threads

         */

        th_1 = thread_run(thread_1, stack[0]+1024);

        thread_setpri(th_1, 100);

        th_2 = thread_run(thread_2, stack[1]+1024);

        thread_setpri(th_2, 101);

        /*

         * Start thread 2

         */

        thread_resume(th_2);

        /*

         * Wait...

         */

        thread_suspend(thread_self());

        return 0;

}