WebSVN - shark - Blame - Rev 318 - /shark/trunk/kernel/int

Rev	Author	Line No.	Line
2	pj	1	/*
		2	* Project: S.Ha.R.K.
		3	*
		4	* Coordinators:
		5	* Giorgio Buttazzo <giorgio@sssup.it>
		6	* Paolo Gai <pj@gandalf.sssup.it>
		7	*
		8	* Authors :
		9	* Paolo Gai <pj@gandalf.sssup.it>
		10	* (see the web pages for full authors list)
		11	*
		12	* ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy)
		13	*
		14	* http://www.sssup.it
		15	* http://retis.sssup.it
		16	* http://shark.sssup.it
		17	*/
		18
		19	/**
		20	------------
318	giacomo	21	CVS : $Id: int_sem.c,v 1.4 2003-11-05 15:05:11 giacomo Exp $
2	pj	22
		23	File: $File$
318	giacomo	24	Revision: $Revision: 1.4 $
		25	Last update: $Date: 2003-11-05 15:05:11 $
2	pj	26	------------
		27
		28	Internal semaphores.
		29
		30	They are different from the Posix semaphores and the mutexes because:
		31	- internal_sem_wait is not a cancellation point
		32	- there are no limits on the semaphores that can be created
		33	(they works like a mutex_t...)
		34	- the queuing policy is FIFO
		35	- Be Careful!
		36	they are made to be fast... so not so many controls are done!!!
		37
		38	**/
		39
		40	/*
		41	* Copyright (C) 2000 Paolo Gai
		42	*
		43	* This program is free software; you can redistribute it and/or modify
		44	* it under the terms of the GNU General Public License as published by
		45	* the Free Software Foundation; either version 2 of the License, or
		46	* (at your option) any later version.
		47	*
		48	* This program is distributed in the hope that it will be useful,
		49	* but WITHOUT ANY WARRANTY; without even the implied warranty of
		50	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
		51	* GNU General Public License for more details.
		52	*
		53	* You should have received a copy of the GNU General Public License
		54	* along with this program; if not, write to the Free Software
		55	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
		56	*
		57	*/
		58
		59
		60	#include <kernel/int_sem.h>
		61	#include <kernel/var.h>
		62	#include <kernel/func.h>
		63
		64	/* Wait status for this library */
		65	#define INTERNAL_SEM_WAIT LIB_STATUS_BASE
		66
		67
		68	void internal_sem_init(internal_sem_t *s, int value)
		69	{
		70	s->count = value;
29	pj	71	iq_init(&s->blocked,&freedesc,0);
2	pj	72	}
		73
		74	void internal_sem_wait(internal_sem_t *s)
		75	{
		76	SYS_FLAGS f;
		77
		78	f = kern_fsave();
		79
		80	if (s->count) {
		81	s->count--;
		82	kern_frestore(f);
		83	return;
		84	}
		85	else { /* We must block exec task */
		86	LEVEL l; /* for readableness only */
		87
		88	proc_table[exec_shadow].context = kern_context_save();
38	pj	89
		90	kern_epilogue_macro();
2	pj	91
		92	l = proc_table[exec_shadow].task_level;
38	pj	93	level_table[l]->public_block(l,exec_shadow);
2	pj	94
		95	/* we insert the task in the semaphore queue */
		96	proc_table[exec_shadow].status = INTERNAL_SEM_WAIT;
29	pj	97	iq_insertlast(exec_shadow,&s->blocked);
2	pj	98
		99	/* and finally we reschedule */
		100	exec = exec_shadow = -1;
		101	scheduler();
		102
		103	ll_context_to(proc_table[exec_shadow].context);
		104	kern_after_dispatch();
		105	kern_frestore(f);
		106	}
		107
		108	}
		109
		110	/* return 0 if the counter is decremented, -1 if not */
		111	int internal_sem_trywait(internal_sem_t *s)
		112	{
		113	SYS_FLAGS f;
		114
		115	f = kern_fsave();
		116
		117	if (s->count) {
		118	s->count--;
		119	kern_frestore(f);
		120	return 0;
		121	}
		122
		123	return -1;
		124	}
		125
		126
		127	void internal_sem_post(internal_sem_t *s)
		128	{
		129	proc_table[exec_shadow].context = kern_context_save();
		130
		131	if (s->blocked.first != -1) {
		132	register PID p;
		133	register LEVEL l;
		134
29	pj	135	p = iq_getfirst(&s->blocked);
2	pj	136	l = proc_table[p].task_level;
38	pj	137	level_table[l]->public_unblock(l,p);
2	pj	138
		139	scheduler();
		140	}
		141	else
		142	s->count++;
		143
		144	kern_context_load(proc_table[exec_shadow].context);
		145	}
		146
		147	int internal_sem_getvalue(internal_sem_t *s)
		148	{
		149	register int returnvalue;
		150	SYS_FLAGS f;
		151
		152	f = kern_fsave();
		153	if (s->blocked.first == -1)
		154	returnvalue = s->count;
		155	else
		156	returnvalue = -1;
		157
		158	kern_frestore(f);
		159	return returnvalue;
		160	}

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(root)/shark/trunk/kernel/int_sem.c @ 1129 - Rev 318