Steven He
/
StringMatchingProtothread
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pt-sem.h@0:544b5f6ad832, 2010-12-01 (annotated)
- Committer:
- StevenHe
- Date:
- Wed Dec 01 04:39:00 2010 +0000
- Revision:
- 0:544b5f6ad832
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| StevenHe | 0:544b5f6ad832 | 1 | /* |
| StevenHe | 0:544b5f6ad832 | 2 | * Copyright (c) 2004, Swedish Institute of Computer Science. |
| StevenHe | 0:544b5f6ad832 | 3 | * All rights reserved. |
| StevenHe | 0:544b5f6ad832 | 4 | * |
| StevenHe | 0:544b5f6ad832 | 5 | * Redistribution and use in source and binary forms, with or without |
| StevenHe | 0:544b5f6ad832 | 6 | * modification, are permitted provided that the following conditions |
| StevenHe | 0:544b5f6ad832 | 7 | * are met: |
| StevenHe | 0:544b5f6ad832 | 8 | * 1. Redistributions of source code must retain the above copyright |
| StevenHe | 0:544b5f6ad832 | 9 | * notice, this list of conditions and the following disclaimer. |
| StevenHe | 0:544b5f6ad832 | 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| StevenHe | 0:544b5f6ad832 | 11 | * notice, this list of conditions and the following disclaimer in the |
| StevenHe | 0:544b5f6ad832 | 12 | * documentation and/or other materials provided with the distribution. |
| StevenHe | 0:544b5f6ad832 | 13 | * 3. Neither the name of the Institute nor the names of its contributors |
| StevenHe | 0:544b5f6ad832 | 14 | * may be used to endorse or promote products derived from this software |
| StevenHe | 0:544b5f6ad832 | 15 | * without specific prior written permission. |
| StevenHe | 0:544b5f6ad832 | 16 | * |
| StevenHe | 0:544b5f6ad832 | 17 | * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND |
| StevenHe | 0:544b5f6ad832 | 18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| StevenHe | 0:544b5f6ad832 | 19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| StevenHe | 0:544b5f6ad832 | 20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE |
| StevenHe | 0:544b5f6ad832 | 21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| StevenHe | 0:544b5f6ad832 | 22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| StevenHe | 0:544b5f6ad832 | 23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| StevenHe | 0:544b5f6ad832 | 24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| StevenHe | 0:544b5f6ad832 | 25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| StevenHe | 0:544b5f6ad832 | 26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| StevenHe | 0:544b5f6ad832 | 27 | * SUCH DAMAGE. |
| StevenHe | 0:544b5f6ad832 | 28 | * |
| StevenHe | 0:544b5f6ad832 | 29 | * This file is part of the protothreads library. |
| StevenHe | 0:544b5f6ad832 | 30 | * |
| StevenHe | 0:544b5f6ad832 | 31 | * Author: Adam Dunkels <adam@sics.se> |
| StevenHe | 0:544b5f6ad832 | 32 | * |
| StevenHe | 0:544b5f6ad832 | 33 | * $Id: pt-sem.h,v 1.2 2005/02/24 10:36:59 adam Exp $ |
| StevenHe | 0:544b5f6ad832 | 34 | */ |
| StevenHe | 0:544b5f6ad832 | 35 | |
| StevenHe | 0:544b5f6ad832 | 36 | /** |
| StevenHe | 0:544b5f6ad832 | 37 | * \addtogroup pt |
| StevenHe | 0:544b5f6ad832 | 38 | * @{ |
| StevenHe | 0:544b5f6ad832 | 39 | */ |
| StevenHe | 0:544b5f6ad832 | 40 | |
| StevenHe | 0:544b5f6ad832 | 41 | /** |
| StevenHe | 0:544b5f6ad832 | 42 | * \defgroup ptsem Protothread semaphores |
| StevenHe | 0:544b5f6ad832 | 43 | * @{ |
| StevenHe | 0:544b5f6ad832 | 44 | * |
| StevenHe | 0:544b5f6ad832 | 45 | * This module implements counting semaphores on top of |
| StevenHe | 0:544b5f6ad832 | 46 | * protothreads. Semaphores are a synchronization primitive that |
| StevenHe | 0:544b5f6ad832 | 47 | * provide two operations: "wait" and "signal". The "wait" operation |
| StevenHe | 0:544b5f6ad832 | 48 | * checks the semaphore counter and blocks the thread if the counter |
| StevenHe | 0:544b5f6ad832 | 49 | * is zero. The "signal" operation increases the semaphore counter but |
| StevenHe | 0:544b5f6ad832 | 50 | * does not block. If another thread has blocked waiting for the |
| StevenHe | 0:544b5f6ad832 | 51 | * semaphore that is signalled, the blocked thread will become |
| StevenHe | 0:544b5f6ad832 | 52 | * runnable again. |
| StevenHe | 0:544b5f6ad832 | 53 | * |
| StevenHe | 0:544b5f6ad832 | 54 | * Semaphores can be used to implement other, more structured, |
| StevenHe | 0:544b5f6ad832 | 55 | * synchronization primitives such as monitors and message |
| StevenHe | 0:544b5f6ad832 | 56 | * queues/bounded buffers (see below). |
| StevenHe | 0:544b5f6ad832 | 57 | * |
| StevenHe | 0:544b5f6ad832 | 58 | * The following example shows how the producer-consumer problem, also |
| StevenHe | 0:544b5f6ad832 | 59 | * known as the bounded buffer problem, can be solved using |
| StevenHe | 0:544b5f6ad832 | 60 | * protothreads and semaphores. Notes on the program follow after the |
| StevenHe | 0:544b5f6ad832 | 61 | * example. |
| StevenHe | 0:544b5f6ad832 | 62 | * |
| StevenHe | 0:544b5f6ad832 | 63 | \code |
| StevenHe | 0:544b5f6ad832 | 64 | #include "pt-sem.h" |
| StevenHe | 0:544b5f6ad832 | 65 | |
| StevenHe | 0:544b5f6ad832 | 66 | #define NUM_ITEMS 32 |
| StevenHe | 0:544b5f6ad832 | 67 | #define BUFSIZE 8 |
| StevenHe | 0:544b5f6ad832 | 68 | |
| StevenHe | 0:544b5f6ad832 | 69 | static struct pt_sem mutex, full, empty; |
| StevenHe | 0:544b5f6ad832 | 70 | |
| StevenHe | 0:544b5f6ad832 | 71 | PT_THREAD(producer(struct pt *pt)) |
| StevenHe | 0:544b5f6ad832 | 72 | { |
| StevenHe | 0:544b5f6ad832 | 73 | static int produced; |
| StevenHe | 0:544b5f6ad832 | 74 | |
| StevenHe | 0:544b5f6ad832 | 75 | PT_BEGIN(pt); |
| StevenHe | 0:544b5f6ad832 | 76 | |
| StevenHe | 0:544b5f6ad832 | 77 | for(produced = 0; produced < NUM_ITEMS; ++produced) { |
| StevenHe | 0:544b5f6ad832 | 78 | |
| StevenHe | 0:544b5f6ad832 | 79 | PT_SEM_WAIT(pt, &full); |
| StevenHe | 0:544b5f6ad832 | 80 | |
| StevenHe | 0:544b5f6ad832 | 81 | PT_SEM_WAIT(pt, &mutex); |
| StevenHe | 0:544b5f6ad832 | 82 | add_to_buffer(produce_item()); |
| StevenHe | 0:544b5f6ad832 | 83 | PT_SEM_SIGNAL(pt, &mutex); |
| StevenHe | 0:544b5f6ad832 | 84 | |
| StevenHe | 0:544b5f6ad832 | 85 | PT_SEM_SIGNAL(pt, &empty); |
| StevenHe | 0:544b5f6ad832 | 86 | } |
| StevenHe | 0:544b5f6ad832 | 87 | |
| StevenHe | 0:544b5f6ad832 | 88 | PT_END(pt); |
| StevenHe | 0:544b5f6ad832 | 89 | } |
| StevenHe | 0:544b5f6ad832 | 90 | |
| StevenHe | 0:544b5f6ad832 | 91 | PT_THREAD(consumer(struct pt *pt)) |
| StevenHe | 0:544b5f6ad832 | 92 | { |
| StevenHe | 0:544b5f6ad832 | 93 | static int consumed; |
| StevenHe | 0:544b5f6ad832 | 94 | |
| StevenHe | 0:544b5f6ad832 | 95 | PT_BEGIN(pt); |
| StevenHe | 0:544b5f6ad832 | 96 | |
| StevenHe | 0:544b5f6ad832 | 97 | for(consumed = 0; consumed < NUM_ITEMS; ++consumed) { |
| StevenHe | 0:544b5f6ad832 | 98 | |
| StevenHe | 0:544b5f6ad832 | 99 | PT_SEM_WAIT(pt, &empty); |
| StevenHe | 0:544b5f6ad832 | 100 | |
| StevenHe | 0:544b5f6ad832 | 101 | PT_SEM_WAIT(pt, &mutex); |
| StevenHe | 0:544b5f6ad832 | 102 | consume_item(get_from_buffer()); |
| StevenHe | 0:544b5f6ad832 | 103 | PT_SEM_SIGNAL(pt, &mutex); |
| StevenHe | 0:544b5f6ad832 | 104 | |
| StevenHe | 0:544b5f6ad832 | 105 | PT_SEM_SIGNAL(pt, &full); |
| StevenHe | 0:544b5f6ad832 | 106 | } |
| StevenHe | 0:544b5f6ad832 | 107 | |
| StevenHe | 0:544b5f6ad832 | 108 | PT_END(pt); |
| StevenHe | 0:544b5f6ad832 | 109 | } |
| StevenHe | 0:544b5f6ad832 | 110 | |
| StevenHe | 0:544b5f6ad832 | 111 | PT_THREAD(driver_thread(struct pt *pt)) |
| StevenHe | 0:544b5f6ad832 | 112 | { |
| StevenHe | 0:544b5f6ad832 | 113 | static struct pt pt_producer, pt_consumer; |
| StevenHe | 0:544b5f6ad832 | 114 | |
| StevenHe | 0:544b5f6ad832 | 115 | PT_BEGIN(pt); |
| StevenHe | 0:544b5f6ad832 | 116 | |
| StevenHe | 0:544b5f6ad832 | 117 | PT_SEM_INIT(&empty, 0); |
| StevenHe | 0:544b5f6ad832 | 118 | PT_SEM_INIT(&full, BUFSIZE); |
| StevenHe | 0:544b5f6ad832 | 119 | PT_SEM_INIT(&mutex, 1); |
| StevenHe | 0:544b5f6ad832 | 120 | |
| StevenHe | 0:544b5f6ad832 | 121 | PT_INIT(&pt_producer); |
| StevenHe | 0:544b5f6ad832 | 122 | PT_INIT(&pt_consumer); |
| StevenHe | 0:544b5f6ad832 | 123 | |
| StevenHe | 0:544b5f6ad832 | 124 | PT_WAIT_THREAD(pt, producer(&pt_producer) & |
| StevenHe | 0:544b5f6ad832 | 125 | consumer(&pt_consumer)); |
| StevenHe | 0:544b5f6ad832 | 126 | |
| StevenHe | 0:544b5f6ad832 | 127 | PT_END(pt); |
| StevenHe | 0:544b5f6ad832 | 128 | } |
| StevenHe | 0:544b5f6ad832 | 129 | \endcode |
| StevenHe | 0:544b5f6ad832 | 130 | * |
| StevenHe | 0:544b5f6ad832 | 131 | * The program uses three protothreads: one protothread that |
| StevenHe | 0:544b5f6ad832 | 132 | * implements the consumer, one thread that implements the producer, |
| StevenHe | 0:544b5f6ad832 | 133 | * and one protothread that drives the two other protothreads. The |
| StevenHe | 0:544b5f6ad832 | 134 | * program uses three semaphores: "full", "empty" and "mutex". The |
| StevenHe | 0:544b5f6ad832 | 135 | * "mutex" semaphore is used to provide mutual exclusion for the |
| StevenHe | 0:544b5f6ad832 | 136 | * buffer, the "empty" semaphore is used to block the consumer is the |
| StevenHe | 0:544b5f6ad832 | 137 | * buffer is empty, and the "full" semaphore is used to block the |
| StevenHe | 0:544b5f6ad832 | 138 | * producer is the buffer is full. |
| StevenHe | 0:544b5f6ad832 | 139 | * |
| StevenHe | 0:544b5f6ad832 | 140 | * The "driver_thread" holds two protothread state variables, |
| StevenHe | 0:544b5f6ad832 | 141 | * "pt_producer" and "pt_consumer". It is important to note that both |
| StevenHe | 0:544b5f6ad832 | 142 | * these variables are declared as <i>static</i>. If the static |
| StevenHe | 0:544b5f6ad832 | 143 | * keyword is not used, both variables are stored on the stack. Since |
| StevenHe | 0:544b5f6ad832 | 144 | * protothreads do not store the stack, these variables may be |
| StevenHe | 0:544b5f6ad832 | 145 | * overwritten during a protothread wait operation. Similarly, both |
| StevenHe | 0:544b5f6ad832 | 146 | * the "consumer" and "producer" protothreads declare their local |
| StevenHe | 0:544b5f6ad832 | 147 | * variables as static, to avoid them being stored on the stack. |
| StevenHe | 0:544b5f6ad832 | 148 | * |
| StevenHe | 0:544b5f6ad832 | 149 | * |
| StevenHe | 0:544b5f6ad832 | 150 | */ |
| StevenHe | 0:544b5f6ad832 | 151 | |
| StevenHe | 0:544b5f6ad832 | 152 | /** |
| StevenHe | 0:544b5f6ad832 | 153 | * \file |
| StevenHe | 0:544b5f6ad832 | 154 | * Couting semaphores implemented on protothreads |
| StevenHe | 0:544b5f6ad832 | 155 | * \author |
| StevenHe | 0:544b5f6ad832 | 156 | * Adam Dunkels <adam@sics.se> |
| StevenHe | 0:544b5f6ad832 | 157 | * |
| StevenHe | 0:544b5f6ad832 | 158 | */ |
| StevenHe | 0:544b5f6ad832 | 159 | |
| StevenHe | 0:544b5f6ad832 | 160 | #ifndef __PT_SEM_H__ |
| StevenHe | 0:544b5f6ad832 | 161 | #define __PT_SEM_H__ |
| StevenHe | 0:544b5f6ad832 | 162 | |
| StevenHe | 0:544b5f6ad832 | 163 | #include "pt.h" |
| StevenHe | 0:544b5f6ad832 | 164 | |
| StevenHe | 0:544b5f6ad832 | 165 | struct pt_sem { |
| StevenHe | 0:544b5f6ad832 | 166 | unsigned int count; |
| StevenHe | 0:544b5f6ad832 | 167 | }; |
| StevenHe | 0:544b5f6ad832 | 168 | |
| StevenHe | 0:544b5f6ad832 | 169 | /** |
| StevenHe | 0:544b5f6ad832 | 170 | * Initialize a semaphore |
| StevenHe | 0:544b5f6ad832 | 171 | * |
| StevenHe | 0:544b5f6ad832 | 172 | * This macro initializes a semaphore with a value for the |
| StevenHe | 0:544b5f6ad832 | 173 | * counter. Internally, the semaphores use an "unsigned int" to |
| StevenHe | 0:544b5f6ad832 | 174 | * represent the counter, and therefore the "count" argument should be |
| StevenHe | 0:544b5f6ad832 | 175 | * within range of an unsigned int. |
| StevenHe | 0:544b5f6ad832 | 176 | * |
| StevenHe | 0:544b5f6ad832 | 177 | * \param s (struct pt_sem *) A pointer to the pt_sem struct |
| StevenHe | 0:544b5f6ad832 | 178 | * representing the semaphore |
| StevenHe | 0:544b5f6ad832 | 179 | * |
| StevenHe | 0:544b5f6ad832 | 180 | * \param c (unsigned int) The initial count of the semaphore. |
| StevenHe | 0:544b5f6ad832 | 181 | * \hideinitializer |
| StevenHe | 0:544b5f6ad832 | 182 | */ |
| StevenHe | 0:544b5f6ad832 | 183 | #define PT_SEM_INIT(s, c) (s)->count = c |
| StevenHe | 0:544b5f6ad832 | 184 | |
| StevenHe | 0:544b5f6ad832 | 185 | /** |
| StevenHe | 0:544b5f6ad832 | 186 | * Wait for a semaphore |
| StevenHe | 0:544b5f6ad832 | 187 | * |
| StevenHe | 0:544b5f6ad832 | 188 | * This macro carries out the "wait" operation on the semaphore. The |
| StevenHe | 0:544b5f6ad832 | 189 | * wait operation causes the protothread to block while the counter is |
| StevenHe | 0:544b5f6ad832 | 190 | * zero. When the counter reaches a value larger than zero, the |
| StevenHe | 0:544b5f6ad832 | 191 | * protothread will continue. |
| StevenHe | 0:544b5f6ad832 | 192 | * |
| StevenHe | 0:544b5f6ad832 | 193 | * \param pt (struct pt *) A pointer to the protothread (struct pt) in |
| StevenHe | 0:544b5f6ad832 | 194 | * which the operation is executed. |
| StevenHe | 0:544b5f6ad832 | 195 | * |
| StevenHe | 0:544b5f6ad832 | 196 | * \param s (struct pt_sem *) A pointer to the pt_sem struct |
| StevenHe | 0:544b5f6ad832 | 197 | * representing the semaphore |
| StevenHe | 0:544b5f6ad832 | 198 | * |
| StevenHe | 0:544b5f6ad832 | 199 | * \hideinitializer |
| StevenHe | 0:544b5f6ad832 | 200 | */ |
| StevenHe | 0:544b5f6ad832 | 201 | #define PT_SEM_WAIT(pt, s) \ |
| StevenHe | 0:544b5f6ad832 | 202 | do { \ |
| StevenHe | 0:544b5f6ad832 | 203 | PT_WAIT_UNTIL(pt, (s)->count > 0); \ |
| StevenHe | 0:544b5f6ad832 | 204 | --(s)->count; \ |
| StevenHe | 0:544b5f6ad832 | 205 | } while(0) |
| StevenHe | 0:544b5f6ad832 | 206 | |
| StevenHe | 0:544b5f6ad832 | 207 | /** |
| StevenHe | 0:544b5f6ad832 | 208 | * Signal a semaphore |
| StevenHe | 0:544b5f6ad832 | 209 | * |
| StevenHe | 0:544b5f6ad832 | 210 | * This macro carries out the "signal" operation on the semaphore. The |
| StevenHe | 0:544b5f6ad832 | 211 | * signal operation increments the counter inside the semaphore, which |
| StevenHe | 0:544b5f6ad832 | 212 | * eventually will cause waiting protothreads to continue executing. |
| StevenHe | 0:544b5f6ad832 | 213 | * |
| StevenHe | 0:544b5f6ad832 | 214 | * \param pt (struct pt *) A pointer to the protothread (struct pt) in |
| StevenHe | 0:544b5f6ad832 | 215 | * which the operation is executed. |
| StevenHe | 0:544b5f6ad832 | 216 | * |
| StevenHe | 0:544b5f6ad832 | 217 | * \param s (struct pt_sem *) A pointer to the pt_sem struct |
| StevenHe | 0:544b5f6ad832 | 218 | * representing the semaphore |
| StevenHe | 0:544b5f6ad832 | 219 | * |
| StevenHe | 0:544b5f6ad832 | 220 | * \hideinitializer |
| StevenHe | 0:544b5f6ad832 | 221 | */ |
| StevenHe | 0:544b5f6ad832 | 222 | #define PT_SEM_SIGNAL(pt, s) ++(s)->count |
| StevenHe | 0:544b5f6ad832 | 223 | |
| StevenHe | 0:544b5f6ad832 | 224 | #endif /* __PT_SEM_H__ */ |
| StevenHe | 0:544b5f6ad832 | 225 | |
| StevenHe | 0:544b5f6ad832 | 226 | /** @} */ |
| StevenHe | 0:544b5f6ad832 | 227 | /** @} */ |
| StevenHe | 0:544b5f6ad832 | 228 |