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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.

 */

/*

 * mutex.c - sample program for mutex with priority inheritance.

 */

/*

 * Senario:

 * This sample shows how the mutex priority is changed when three

 * different threads lock two mutexes at same time.

 *

 * The priority of each thread are as follows.

 *    Thread1 - priority 100 (highest)

 *    Thread2 - priority 101

 *    Thread3 - priority 102

 *

 * Thread priority and state are changed as follows.

 *

 *    Action                    Thread 1  Thread 2  Thread 3  Mutex A  Mutex B

 *    ------------------------  --------  --------  --------  -------  -------

 * 1) Thread 3 locks mutex A    susp/100  susp/101  run /102  owner=3

 * 2) Thread 2 locks mutex B    susp/100  run /101  run /102  owner=3  owner=2

 * 3) Thread 2 locks mutex A    susp/100  wait/101  run /101* owner=3  owner=2

 * 4) Thread 1 locks mutex B    wait/100  wait/100* run /100* owner=3  owner=2

 * 5) Thread 3 unlocks mutex A  wait/100  run /100  run /102* owner=2* owner=2

 * 6) Thread 2 unlocks mutex B  run /100* run /100  run /102  owner=2  owner=1*

 * 7) Thread 2 unlocks mutex A  run /100  run /100  run /102           owner=1

 * 8) Thread 1 unlocks mutex B  wait/100  run /101  run /102

 *

 */

#include <sys/prex.h>

#include <stdio.h>

static char stack[3][1024];

static thread_t th_1, th_2, th_3;

static mutex_t mtx_A, mtx_B;

static void

dump_pri(void)

{

        int pri;

        if (thread_getpri(th_1, &pri) == 0)

                printf("th_1: pri=%d\n", pri);

        if (thread_getpri(th_2, &pri) == 0)

                printf("th_2: pri=%d\n", pri);

        if (thread_getpri(th_3, &pri) == 0)

                printf("th_3: pri=%d\n", pri);

}

thread_t

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

{

        thread_t t;

        if (thread_create(task_self(), &t) != 0)

                panic("thread_create is failed");

        if (thread_load(t, start, stack) != 0)

                panic("thread_load is failed");

        return t;

}

/*

 * Thread 1 - Priority = 100

 */

static void

thread_1(void)

{

        printf("thread_1: starting\n");

        /*

         * 4) Lock mutex B

         *

         * Priority inheritance:

         *    Thread 2... Pri 101 -> 100

         *    Thread 3... Pri 101 -> 100

         */

        printf("thread_1: 4) lock B\n");

        mutex_lock(&mtx_B);

        printf("thread_1: running\n");

        dump_pri();

        /*

         * 8) Unlock mutex B

         */

        printf("thread_1: 7) unlock B\n");

        mutex_unlock(&mtx_B);

        dump_pri();

        printf("thread_1: exit\n");

        thread_terminate(th_1);

}

/*

 * Thread 2 - Priority = 101

 */

static void

thread_2(void)

{

        printf("thread_2: starting\n");

        /*

         * 2) Lock mutex B

         */

        printf("thread_2: 2) lock B\n");

        mutex_lock(&mtx_B);

        dump_pri();

        /*

         * 3) Lock mutex A (Switch to thread 3)

         *

         * Priority inheritance:

         *    Thread 3... Pri 102 -> 101

         */

        printf("thread_2: 3) lock A\n");

        mutex_lock(&mtx_A);

        printf("thread_2: running\n");

        dump_pri();

        /*

         * 6) Unlock mutex B

         */

        printf("thread_2: 6) unlock B\n");

        mutex_unlock(&mtx_B);

        dump_pri();

        /*

         * 7) Unlock mutex A

         */

        printf("thread_2: 8) unlock A\n");

        mutex_unlock(&mtx_A);

        printf("thread_2: exit\n");

        thread_terminate(th_2);

}

/*

 * Thread 3 - Priority = 102

 */

static void

thread_3(void)

{

        printf("thread_3: start\n");

        /*

         * 1) Lock mutex A

         */

        printf("thread_3: 1) lock A\n");

        mutex_lock(&mtx_A);

        dump_pri();

        /*

         * Start thread 2

         */

        thread_resume(th_2);

        /*

         * Check priority

         */

        printf("thread_3: running-1\n");

        dump_pri();

        /*

         * Start thread 1

         */

        thread_resume(th_1);

        printf("thread_3: running-2\n");

        dump_pri();

        /*

         * 5) Unlock mutex A

         */

        printf("thread_3: 5) unlock A\n");

        mutex_unlock(&mtx_A);

        dump_pri();

        printf("thread_3: exit\n");

        thread_terminate(th_3);

}

int

main(int argc, char *argv[])

{

        printf("Mutex sample 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);

        th_3 = thread_run(thread_3, stack[2]+1024);

        thread_setpri(th_3, 102);

        dump_pri();

        /*

         * Start lowest priority thread

         */

        thread_resume(th_3);

        /*

         * Wait...

         */

        thread_suspend(thread_self());

        return 0;

}