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Annotation of prex-old/usr/sample/mutex/mutex.c, Revision 1.1.1.1

1.1       nbrk        1: /*
                      2:  * Copyright (c) 2005, Kohsuke Ohtani
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms, with or without
                      6:  * modification, are permitted provided that the following conditions
                      7:  * are met:
                      8:  * 1. Redistributions of source code must retain the above copyright
                      9:  *    notice, this list of conditions and the following disclaimer.
                     10:  * 2. Redistributions in binary form must reproduce the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer in the
                     12:  *    documentation and/or other materials provided with the distribution.
                     13:  * 3. Neither the name of the author nor the names of any co-contributors
                     14:  *    may be used to endorse or promote products derived from this software
                     15:  *    without specific prior written permission.
                     16:  *
                     17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     27:  * SUCH DAMAGE.
                     28:  */
                     29:
                     30: /*
                     31:  * mutex.c - sample program for mutex with priority inheritence.
                     32:  */
                     33:
                     34: /*
                     35:  * Senario:
                     36:  * This sample shows how the mutex priority is changed when three
                     37:  * different threads lock two mutexes at same time.
                     38:  *
                     39:  * The priority of each thread are as follow.
                     40:  *    Thread1 - priority 100 (highest)
                     41:  *    Thread2 - priority 101
                     42:  *    Thread3 - priority 102
                     43:  *
                     44:  * Thread priority and state are changed as follow.
                     45:  *
                     46:  *    Action                    Thread 1  Thread 2  Thread 3  Mutex A  Mutex B
                     47:  *    ------------------------  --------  --------  --------  -------  -------
                     48:  * 1) Thread 3 locks mutex A    susp/100  susp/101  run /102  owner=3
                     49:  * 2) Thread 2 locks mutex B    susp/100  run /101  run /102  owner=3  owner=2
                     50:  * 3) Thread 2 locks mutex A    susp/100  wait/101  run /101* owner=3  owner=2
                     51:  * 4) Thread 1 locks mutex B    wait/100  wait/100* run /100* owner=3  owner=2
                     52:  * 5) Thread 3 unlocks mutex A  wait/100  run /100  run /102* owner=2* owner=2
                     53:  * 6) Thread 2 unlocks mutex B  run /100* run /100  run /102  owner=2  owner=1*
                     54:  * 7) Thread 2 unlocks mutex A  run /100  run /100  run /102           owner=1
                     55:  * 8) Thread 1 unlocks mutex B  wait/100  run /101  run /102
                     56:  *
                     57:  */
                     58:
                     59: #include <prex/prex.h>
                     60: #include <stdio.h>
                     61:
                     62: static char stack[3][1024];
                     63: static thread_t th_1, th_2, th_3;
                     64: static mutex_t mtx_A, mtx_B;
                     65:
                     66: static void
                     67: dump_prio(void)
                     68: {
                     69:        int prio;
                     70:
                     71:        if (thread_getprio(th_1, &prio) == 0)
                     72:                printf("th_1: prio=%d\n", prio);
                     73:
                     74:        if (thread_getprio(th_2, &prio) == 0)
                     75:                printf("th_2: prio=%d\n", prio);
                     76:
                     77:        if (thread_getprio(th_3, &prio) == 0)
                     78:                printf("th_3: prio=%d\n", prio);
                     79: }
                     80:
                     81: thread_t
                     82: thread_run(void (*start)(void), void *stack)
                     83: {
                     84:        thread_t th;
                     85:
                     86:        if (thread_create(task_self(), &th) != 0)
                     87:                panic("thread_create is failed");
                     88:
                     89:        if (thread_load(th, start, stack) != 0)
                     90:                panic("thread_load is failed");
                     91:
                     92:        return th;
                     93: }
                     94:
                     95: /*
                     96:  * Thread 1 - Priority = 100
                     97:  */
                     98: static void
                     99: thread_1(void)
                    100: {
                    101:        printf("thread_1: starting\n");
                    102:
                    103:        /*
                    104:         * 4) Lock mutex B
                    105:         *
                    106:         * Priority inheritance:
                    107:         *    Thread 2... Prio 101 -> 100
                    108:         *    Thread 3... Prio 101 -> 100
                    109:         */
                    110:        printf("thread_1: 4) lock B\n");
                    111:        mutex_lock(&mtx_B);
                    112:
                    113:        printf("thread_1: running\n");
                    114:        dump_prio();
                    115:
                    116:        /*
                    117:         * 8) Unlock mutex B
                    118:         */
                    119:        printf("thread_1: 7) unlock B\n");
                    120:        mutex_unlock(&mtx_B);
                    121:
                    122:        dump_prio();
                    123:        printf("thread_1: exit\n");
                    124:        thread_terminate(th_1);
                    125: }
                    126:
                    127: /*
                    128:  * Thread 2 - Priority = 101
                    129:  */
                    130: static void
                    131: thread_2(void)
                    132: {
                    133:        printf("thread_2: starting\n");
                    134:
                    135:        /*
                    136:         * 2) Lock mutex B
                    137:         */
                    138:        printf("thread_2: 2) lock B\n");
                    139:        mutex_lock(&mtx_B);
                    140:        dump_prio();
                    141:
                    142:        /*
                    143:         * 3) Lock mutex A (Switch to thread 3)
                    144:         *
                    145:         * Priority inheritance:
                    146:         *    Thread 3... Prio 102 -> 101
                    147:         */
                    148:        printf("thread_2: 3) lock A\n");
                    149:        mutex_lock(&mtx_A);
                    150:
                    151:        printf("thread_2: running\n");
                    152:        dump_prio();
                    153:
                    154:        /*
                    155:         * 6) Unlock mutex B
                    156:         */
                    157:        printf("thread_2: 6) unlock B\n");
                    158:        mutex_unlock(&mtx_B);
                    159:
                    160:        dump_prio();
                    161:
                    162:        /*
                    163:         * 7) Unlock mutex A
                    164:         */
                    165:        printf("thread_2: 8) unlock A\n");
                    166:        mutex_unlock(&mtx_A);
                    167:
                    168:        printf("thread_2: exit\n");
                    169:        thread_terminate(th_2);
                    170: }
                    171:
                    172:
                    173: /*
                    174:  * Thread 3 - Priority = 102
                    175:  */
                    176: static void
                    177: thread_3(void)
                    178: {
                    179:        printf("thread_3: start\n");
                    180:
                    181:        /*
                    182:         * 1) Lock mutex A
                    183:         */
                    184:        printf("thread_3: 1) lock A\n");
                    185:        mutex_lock(&mtx_A);
                    186:        dump_prio();
                    187:
                    188:        /*
                    189:         * Start thread 2
                    190:         */
                    191:        thread_resume(th_2);
                    192:
                    193:        /*
                    194:         * Check priority
                    195:         */
                    196:        printf("thread_3: running-1\n");
                    197:        dump_prio();
                    198:
                    199:        /*
                    200:         * Start thread 1
                    201:         */
                    202:        thread_resume(th_1);
                    203:        printf("thread_3: running-2\n");
                    204:        dump_prio();
                    205:
                    206:        /*
                    207:         * 5) Unlock mutex A
                    208:         */
                    209:        printf("thread_3: 5) unlock A\n");
                    210:        mutex_unlock(&mtx_A);
                    211:
                    212:        dump_prio();
                    213:        printf("thread_3: exit\n");
                    214:        thread_terminate(th_3);
                    215: }
                    216:
                    217: int
                    218: main(int argc, char *argv[])
                    219: {
                    220:        printf("Mutex sample program\n");
                    221:
                    222:        /*
                    223:         * Boost priority of this thread
                    224:         */
                    225:        thread_setprio(thread_self(), 90);
                    226:
                    227:        /*
                    228:         * Initialize mutexes.
                    229:         */
                    230:        mutex_init(&mtx_A);
                    231:        mutex_init(&mtx_B);
                    232:
                    233:        /*
                    234:         * Create new threads
                    235:         */
                    236:        th_1 = thread_run(thread_1, stack[0]+1024);
                    237:        thread_setprio(th_1, 100);
                    238:
                    239:        th_2 = thread_run(thread_2, stack[1]+1024);
                    240:        thread_setprio(th_2, 101);
                    241:
                    242:        th_3 = thread_run(thread_3, stack[2]+1024);
                    243:        thread_setprio(th_3, 102);
                    244:
                    245:        dump_prio();
                    246:
                    247:        /*
                    248:         * Start lowest priority thread
                    249:         */
                    250:        thread_resume(th_3);
                    251:
                    252:        /*
                    253:         * Wait...
                    254:         */
                    255:        thread_suspend(thread_self());
                    256:
                    257:        return 0;
                    258: }

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