TouchSensorMT_2 - Homework2_3Multithreads_YuwenSun

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Homework2_3Multithreads_YuwenSun

pt-sem.h@0:edab293d7652, 2010-11-30 (annotated)

Committer:: sun831011
Date:: Tue Nov 30 22:19:29 2010 +0000
Revision:: 0:edab293d7652

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sun831011	0:edab293d7652	1	/*
sun831011	0:edab293d7652	2	* Copyright (c) 2004, Swedish Institute of Computer Science.
sun831011	0:edab293d7652	3	* All rights reserved.
sun831011	0:edab293d7652	4	*
sun831011	0:edab293d7652	5	* Redistribution and use in source and binary forms, with or without
sun831011	0:edab293d7652	6	* modification, are permitted provided that the following conditions
sun831011	0:edab293d7652	7	* are met:
sun831011	0:edab293d7652	8	* 1. Redistributions of source code must retain the above copyright
sun831011	0:edab293d7652	9	* notice, this list of conditions and the following disclaimer.
sun831011	0:edab293d7652	10	* 2. Redistributions in binary form must reproduce the above copyright
sun831011	0:edab293d7652	11	* notice, this list of conditions and the following disclaimer in the
sun831011	0:edab293d7652	12	* documentation and/or other materials provided with the distribution.
sun831011	0:edab293d7652	13	* 3. Neither the name of the Institute nor the names of its contributors
sun831011	0:edab293d7652	14	* may be used to endorse or promote products derived from this software
sun831011	0:edab293d7652	15	* without specific prior written permission.
sun831011	0:edab293d7652	16	*
sun831011	0:edab293d7652	17	* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
sun831011	0:edab293d7652	18	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
sun831011	0:edab293d7652	19	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
sun831011	0:edab293d7652	20	* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
sun831011	0:edab293d7652	21	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
sun831011	0:edab293d7652	22	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
sun831011	0:edab293d7652	23	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
sun831011	0:edab293d7652	24	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
sun831011	0:edab293d7652	25	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
sun831011	0:edab293d7652	26	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
sun831011	0:edab293d7652	27	* SUCH DAMAGE.
sun831011	0:edab293d7652	28	*
sun831011	0:edab293d7652	29	* This file is part of the protothreads library.
sun831011	0:edab293d7652	30	*
sun831011	0:edab293d7652	31	* Author: Adam Dunkels <adam@sics.se>
sun831011	0:edab293d7652	32	*
sun831011	0:edab293d7652	33	* $Id: pt-sem.h,v 1.2 2005/02/24 10:36:59 adam Exp $
sun831011	0:edab293d7652	34	*/
sun831011	0:edab293d7652	35
sun831011	0:edab293d7652	36	/**
sun831011	0:edab293d7652	37	* \addtogroup pt
sun831011	0:edab293d7652	38	* @{
sun831011	0:edab293d7652	39	*/
sun831011	0:edab293d7652	40
sun831011	0:edab293d7652	41	/**
sun831011	0:edab293d7652	42	* \defgroup ptsem Protothread semaphores
sun831011	0:edab293d7652	43	* @{
sun831011	0:edab293d7652	44	*
sun831011	0:edab293d7652	45	* This module implements counting semaphores on top of
sun831011	0:edab293d7652	46	* protothreads. Semaphores are a synchronization primitive that
sun831011	0:edab293d7652	47	* provide two operations: "wait" and "signal". The "wait" operation
sun831011	0:edab293d7652	48	* checks the semaphore counter and blocks the thread if the counter
sun831011	0:edab293d7652	49	* is zero. The "signal" operation increases the semaphore counter but
sun831011	0:edab293d7652	50	* does not block. If another thread has blocked waiting for the
sun831011	0:edab293d7652	51	* semaphore that is signalled, the blocked thread will become
sun831011	0:edab293d7652	52	* runnable again.
sun831011	0:edab293d7652	53	*
sun831011	0:edab293d7652	54	* Semaphores can be used to implement other, more structured,
sun831011	0:edab293d7652	55	* synchronization primitives such as monitors and message
sun831011	0:edab293d7652	56	* queues/bounded buffers (see below).
sun831011	0:edab293d7652	57	*
sun831011	0:edab293d7652	58	* The following example shows how the producer-consumer problem, also
sun831011	0:edab293d7652	59	* known as the bounded buffer problem, can be solved using
sun831011	0:edab293d7652	60	* protothreads and semaphores. Notes on the program follow after the
sun831011	0:edab293d7652	61	* example.
sun831011	0:edab293d7652	62	*
sun831011	0:edab293d7652	63	\code
sun831011	0:edab293d7652	64	#include "pt-sem.h"
sun831011	0:edab293d7652	65
sun831011	0:edab293d7652	66	#define NUM_ITEMS 32
sun831011	0:edab293d7652	67	#define BUFSIZE 8
sun831011	0:edab293d7652	68
sun831011	0:edab293d7652	69	static struct pt_sem mutex, full, empty;
sun831011	0:edab293d7652	70
sun831011	0:edab293d7652	71	PT_THREAD(producer(struct pt *pt))
sun831011	0:edab293d7652	72	{
sun831011	0:edab293d7652	73	static int produced;
sun831011	0:edab293d7652	74
sun831011	0:edab293d7652	75	PT_BEGIN(pt);
sun831011	0:edab293d7652	76
sun831011	0:edab293d7652	77	for(produced = 0; produced < NUM_ITEMS; ++produced) {
sun831011	0:edab293d7652	78
sun831011	0:edab293d7652	79	PT_SEM_WAIT(pt, &full);
sun831011	0:edab293d7652	80
sun831011	0:edab293d7652	81	PT_SEM_WAIT(pt, &mutex);
sun831011	0:edab293d7652	82	add_to_buffer(produce_item());
sun831011	0:edab293d7652	83	PT_SEM_SIGNAL(pt, &mutex);
sun831011	0:edab293d7652	84
sun831011	0:edab293d7652	85	PT_SEM_SIGNAL(pt, &empty);
sun831011	0:edab293d7652	86	}
sun831011	0:edab293d7652	87
sun831011	0:edab293d7652	88	PT_END(pt);
sun831011	0:edab293d7652	89	}
sun831011	0:edab293d7652	90
sun831011	0:edab293d7652	91	PT_THREAD(consumer(struct pt *pt))
sun831011	0:edab293d7652	92	{
sun831011	0:edab293d7652	93	static int consumed;
sun831011	0:edab293d7652	94
sun831011	0:edab293d7652	95	PT_BEGIN(pt);
sun831011	0:edab293d7652	96
sun831011	0:edab293d7652	97	for(consumed = 0; consumed < NUM_ITEMS; ++consumed) {
sun831011	0:edab293d7652	98
sun831011	0:edab293d7652	99	PT_SEM_WAIT(pt, &empty);
sun831011	0:edab293d7652	100
sun831011	0:edab293d7652	101	PT_SEM_WAIT(pt, &mutex);
sun831011	0:edab293d7652	102	consume_item(get_from_buffer());
sun831011	0:edab293d7652	103	PT_SEM_SIGNAL(pt, &mutex);
sun831011	0:edab293d7652	104
sun831011	0:edab293d7652	105	PT_SEM_SIGNAL(pt, &full);
sun831011	0:edab293d7652	106	}
sun831011	0:edab293d7652	107
sun831011	0:edab293d7652	108	PT_END(pt);
sun831011	0:edab293d7652	109	}
sun831011	0:edab293d7652	110
sun831011	0:edab293d7652	111	PT_THREAD(driver_thread(struct pt *pt))
sun831011	0:edab293d7652	112	{
sun831011	0:edab293d7652	113	static struct pt pt_producer, pt_consumer;
sun831011	0:edab293d7652	114
sun831011	0:edab293d7652	115	PT_BEGIN(pt);
sun831011	0:edab293d7652	116
sun831011	0:edab293d7652	117	PT_SEM_INIT(&empty, 0);
sun831011	0:edab293d7652	118	PT_SEM_INIT(&full, BUFSIZE);
sun831011	0:edab293d7652	119	PT_SEM_INIT(&mutex, 1);
sun831011	0:edab293d7652	120
sun831011	0:edab293d7652	121	PT_INIT(&pt_producer);
sun831011	0:edab293d7652	122	PT_INIT(&pt_consumer);
sun831011	0:edab293d7652	123
sun831011	0:edab293d7652	124	PT_WAIT_THREAD(pt, producer(&pt_producer) &
sun831011	0:edab293d7652	125	consumer(&pt_consumer));
sun831011	0:edab293d7652	126
sun831011	0:edab293d7652	127	PT_END(pt);
sun831011	0:edab293d7652	128	}
sun831011	0:edab293d7652	129	\endcode
sun831011	0:edab293d7652	130	*
sun831011	0:edab293d7652	131	* The program uses three protothreads: one protothread that
sun831011	0:edab293d7652	132	* implements the consumer, one thread that implements the producer,
sun831011	0:edab293d7652	133	* and one protothread that drives the two other protothreads. The
sun831011	0:edab293d7652	134	* program uses three semaphores: "full", "empty" and "mutex". The
sun831011	0:edab293d7652	135	* "mutex" semaphore is used to provide mutual exclusion for the
sun831011	0:edab293d7652	136	* buffer, the "empty" semaphore is used to block the consumer is the
sun831011	0:edab293d7652	137	* buffer is empty, and the "full" semaphore is used to block the
sun831011	0:edab293d7652	138	* producer is the buffer is full.
sun831011	0:edab293d7652	139	*
sun831011	0:edab293d7652	140	* The "driver_thread" holds two protothread state variables,
sun831011	0:edab293d7652	141	* "pt_producer" and "pt_consumer". It is important to note that both
sun831011	0:edab293d7652	142	* these variables are declared as <i>static</i>. If the static
sun831011	0:edab293d7652	143	* keyword is not used, both variables are stored on the stack. Since
sun831011	0:edab293d7652	144	* protothreads do not store the stack, these variables may be
sun831011	0:edab293d7652	145	* overwritten during a protothread wait operation. Similarly, both
sun831011	0:edab293d7652	146	* the "consumer" and "producer" protothreads declare their local
sun831011	0:edab293d7652	147	* variables as static, to avoid them being stored on the stack.
sun831011	0:edab293d7652	148	*
sun831011	0:edab293d7652	149	*
sun831011	0:edab293d7652	150	*/
sun831011	0:edab293d7652	151
sun831011	0:edab293d7652	152	/**
sun831011	0:edab293d7652	153	* \file
sun831011	0:edab293d7652	154	* Couting semaphores implemented on protothreads
sun831011	0:edab293d7652	155	* \author
sun831011	0:edab293d7652	156	* Adam Dunkels <adam@sics.se>
sun831011	0:edab293d7652	157	*
sun831011	0:edab293d7652	158	*/
sun831011	0:edab293d7652	159
sun831011	0:edab293d7652	160	#ifndef __PT_SEM_H__
sun831011	0:edab293d7652	161	#define __PT_SEM_H__
sun831011	0:edab293d7652	162
sun831011	0:edab293d7652	163	#include "pt.h"
sun831011	0:edab293d7652	164
sun831011	0:edab293d7652	165	struct pt_sem {
sun831011	0:edab293d7652	166	unsigned int count;
sun831011	0:edab293d7652	167	};
sun831011	0:edab293d7652	168
sun831011	0:edab293d7652	169	/**
sun831011	0:edab293d7652	170	* Initialize a semaphore
sun831011	0:edab293d7652	171	*
sun831011	0:edab293d7652	172	* This macro initializes a semaphore with a value for the
sun831011	0:edab293d7652	173	* counter. Internally, the semaphores use an "unsigned int" to
sun831011	0:edab293d7652	174	* represent the counter, and therefore the "count" argument should be
sun831011	0:edab293d7652	175	* within range of an unsigned int.
sun831011	0:edab293d7652	176	*
sun831011	0:edab293d7652	177	* \param s (struct pt_sem *) A pointer to the pt_sem struct
sun831011	0:edab293d7652	178	* representing the semaphore
sun831011	0:edab293d7652	179	*
sun831011	0:edab293d7652	180	* \param c (unsigned int) The initial count of the semaphore.
sun831011	0:edab293d7652	181	* \hideinitializer
sun831011	0:edab293d7652	182	*/
sun831011	0:edab293d7652	183	#define PT_SEM_INIT(s, c) (s)->count = c
sun831011	0:edab293d7652	184
sun831011	0:edab293d7652	185	/**
sun831011	0:edab293d7652	186	* Wait for a semaphore
sun831011	0:edab293d7652	187	*
sun831011	0:edab293d7652	188	* This macro carries out the "wait" operation on the semaphore. The
sun831011	0:edab293d7652	189	* wait operation causes the protothread to block while the counter is
sun831011	0:edab293d7652	190	* zero. When the counter reaches a value larger than zero, the
sun831011	0:edab293d7652	191	* protothread will continue.
sun831011	0:edab293d7652	192	*
sun831011	0:edab293d7652	193	* \param pt (struct pt *) A pointer to the protothread (struct pt) in
sun831011	0:edab293d7652	194	* which the operation is executed.
sun831011	0:edab293d7652	195	*
sun831011	0:edab293d7652	196	* \param s (struct pt_sem *) A pointer to the pt_sem struct
sun831011	0:edab293d7652	197	* representing the semaphore
sun831011	0:edab293d7652	198	*
sun831011	0:edab293d7652	199	* \hideinitializer
sun831011	0:edab293d7652	200	*/
sun831011	0:edab293d7652	201	#define PT_SEM_WAIT(pt, s) \
sun831011	0:edab293d7652	202	do { \
sun831011	0:edab293d7652	203	PT_WAIT_UNTIL(pt, (s)->count > 0); \
sun831011	0:edab293d7652	204	--(s)->count; \
sun831011	0:edab293d7652	205	} while(0)
sun831011	0:edab293d7652	206
sun831011	0:edab293d7652	207	/**
sun831011	0:edab293d7652	208	* Signal a semaphore
sun831011	0:edab293d7652	209	*
sun831011	0:edab293d7652	210	* This macro carries out the "signal" operation on the semaphore. The
sun831011	0:edab293d7652	211	* signal operation increments the counter inside the semaphore, which
sun831011	0:edab293d7652	212	* eventually will cause waiting protothreads to continue executing.
sun831011	0:edab293d7652	213	*
sun831011	0:edab293d7652	214	* \param pt (struct pt *) A pointer to the protothread (struct pt) in
sun831011	0:edab293d7652	215	* which the operation is executed.
sun831011	0:edab293d7652	216	*
sun831011	0:edab293d7652	217	* \param s (struct pt_sem *) A pointer to the pt_sem struct
sun831011	0:edab293d7652	218	* representing the semaphore
sun831011	0:edab293d7652	219	*
sun831011	0:edab293d7652	220	* \hideinitializer
sun831011	0:edab293d7652	221	*/
sun831011	0:edab293d7652	222	#define PT_SEM_SIGNAL(pt, s) ++(s)->count
sun831011	0:edab293d7652	223
sun831011	0:edab293d7652	224	#endif /* __PT_SEM_H__ */
sun831011	0:edab293d7652	225
sun831011	0:edab293d7652	226	/** @} */
sun831011	0:edab293d7652	227	/** @} */
sun831011	0:edab293d7652	228

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	30 Nov 2010
Imports:	2
Forks:	0
Commits:	1
Dependents:	0
Dependencies:	1
Followers:	1

pt-sem.h@0:edab293d7652, 2010-11-30 (annotated)

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