WebSVN - shark - Blame - Rev 38 - /shark/trunk/kernel/modules/sem.c

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	* Massimiliano Giorgi <massy@gandalf.sssup.it>
		11	* Luca Abeni <luca@gandalf.sssup.it>
		12	* (see the web pages for full authors list)
		13	*
		14	* ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy)
		15	*
		16	* http://www.sssup.it
		17	* http://retis.sssup.it
		18	* http://shark.sssup.it
		19	*/
		20
		21	/**
		22	------------
38	pj	23	CVS : $Id: sem.c,v 1.3 2003-01-07 17:07:51 pj Exp $
2	pj	24
		25	File: $File$
38	pj	26	Revision: $Revision: 1.3 $
		27	Last update: $Date: 2003-01-07 17:07:51 $
2	pj	28	------------
		29
		30	This file contains the Hartik 3.3.1 Semaphore functions
		31
		32	Author: Giuseppe Lipari
		33
		34	Semaphores:
		35	this is the generalized version of the primitives signal & wait
		36	In this case, the user can specify the number to inc/dec the
		37	semaphore's counter. It is useful in the buffer management
		38	(see port section)
		39
		40	**/
		41
		42	/*
		43	* Copyright (C) 2000 Paolo Gai
		44	*
		45	* This program is free software; you can redistribute it and/or modify
		46	* it under the terms of the GNU General Public License as published by
		47	* the Free Software Foundation; either version 2 of the License, or
		48	* (at your option) any later version.
		49	*
		50	* This program is distributed in the hope that it will be useful,
		51	* but WITHOUT ANY WARRANTY; without even the implied warranty of
		52	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
		53	* GNU General Public License for more details.
		54	*
		55	* You should have received a copy of the GNU General Public License
		56	* along with this program; if not, write to the Free Software
		57	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
		58	*
		59	*/
		60
		61
		62	#include <stdarg.h>
		63	#include <modules/sem.h>
		64	#include <kernel/config.h>
		65	#include <ll/ll.h>
		66	#include <ll/string.h>
		67	#include <kernel/const.h>
		68	#include <sys/types.h>
		69	#include <kernel/descr.h>
		70	#include <kernel/var.h>
		71	#include <kernel/func.h>
		72	#include <kernel/trace.h>
		73	#include <limits.h>
		74	#include <fcntl.h>
		75
		76
		77	/* Semaphores descriptor tables */
		78	static struct sem_des {
		79	char name; / a name, for named semaphores */
		80	int index; /* an index for sem_open, containing the sem number */
		81	int count; /* the semaphore counter */
29	pj	82	IQUEUE blocked; /* the blocked processes queue */
2	pj	83	int next; /* the semaphore queue */
		84	BYTE used; /* 1 if the semaphore is used */
		85	} sem_table[SEM_NSEMS_MAX];
		86
		87
		88	/* this -IS- an extension to the proc_table!!! */
		89	static struct {
		90	int decsem; /* the value required in sem_xwait */
		91	int sem; /* the semaphore on whitch the process is blocked */
		92	} sp_table[MAX_PROC];
		93
29	pj	94	static int free_sem; /* Queue of free sem */
2	pj	95
		96
		97
		98	/----------------------------------------------------------------------/
		99	/* Cancellation test for semaphores */
		100	/----------------------------------------------------------------------/
		101
		102	/* this is the test that is done when a task is being killed
		103	and it is waiting on a sigwait */
		104	static int semwait_cancellation_point(PID i, void *arg)
		105	{
		106	LEVEL l;
		107
		108	if (proc_table[i].status == WAIT_SEM) {
		109	/* the task that have to be killed is waiting on a sig_wait.
		110	we reset the data structures set in sig_wait and then when the
		111	task will return on the sig_wait it will fall into a
		112	task_testcancel */
		113
		114	/* extract the process from the semaphore queue... */
29	pj	115	iq_extract(i,&sem_table[ sp_table[i].sem ].blocked);
2	pj	116
		117	l = proc_table[i].task_level;
38	pj	118	level_table[l]->public_unblock(l,i);
2	pj	119
		120	return 1;
		121	}
		122
		123	return 0;
		124	}
		125
		126	/----------------------------------------------------------------------/
		127	/* Init the semaphoric structures */
		128	/----------------------------------------------------------------------/
		129	void SEM_register_module(void)
		130	{
		131	int i;
		132
		133	for (i = 0; i < SEM_NSEMS_MAX; i++) {
		134	sem_table[i].name = NULL;
		135	sem_table[i].index = i;
		136	sem_table[i].count = 0;
29	pj	137	iq_init(&sem_table[i].blocked, &freedesc, 0);
2	pj	138	sem_table[i].next = i+1;
		139	sem_table[i].used = 0;
		140	}
		141	sem_table[SEM_NSEMS_MAX-1].next = NIL;
		142	free_sem = 0;
		143
		144	register_cancellation_point(semwait_cancellation_point, NULL);
		145	}
		146
		147	/----------------------------------------------------------------------/
		148	/* Allocate a semaphoric descriptor and sets the counter to n */
		149	/----------------------------------------------------------------------/
		150
		151	// the pshared parameter is NRQ for PSE52
		152	int sem_init(sem_t *sem, int pshared, unsigned int value)
		153	{
		154	if (value > SEM_VALUE_MAX)
		155	return EINVAL;
		156
		157	kern_cli();
		158	*sem = free_sem;
		159	if (*sem != NIL) {
		160	free_sem = sem_table[*sem].next;
		161	sem_table[*sem].name = NULL;
		162	sem_table[*sem].count = value;
29	pj	163	iq_init(&sem_table[*sem].blocked, &freedesc, 0);
2	pj	164	sem_table[*sem].used = 1;
		165	}
		166	else {
		167	errno = ENOSPC;
		168	kern_sti();
		169	return -1;
		170	}
		171	kern_sti();
		172	return 0;
		173	}
		174
		175	/----------------------------------------------------------------------/
		176	/* Frees a semaphores descriptor */
		177	/----------------------------------------------------------------------/
		178	int sem_destroy(sem_t *sem)
		179	{
		180	kern_cli();
		181
		182	if (sem < 0 \|\| sem >= SEM_NSEMS_MAX \|\| !sem_table[*sem].used) {
		183	errno = EINVAL;
		184	kern_sti();
		185	return -1;
		186	}
		187
		188	if (sem_table[*sem].blocked.first != NIL) {
		189	errno = EBUSY;
		190	kern_sti();
		191	return -1;
		192	}
		193
		194	sem_table[*sem].used = 0;
		195	sem_table[*sem].next = free_sem;
		196	free_sem = *sem;
		197
		198	kern_sti();
		199	return 0;
		200	}
		201
		202	/----------------------------------------------------------------------/
		203	/* Allocate a named semaphore */
		204	/----------------------------------------------------------------------/
		205
		206	// the pshared parameter is NRQ for PSE52
		207	sem_t sem_open(const char name, int oflag, ...)
		208	{
		209	int i, j;
		210	int found = 0;
		211	mode_t m;
		212	sem_t sem;
		213
		214	kern_cli();
		215
		216	for (i = 0; i < SEM_NSEMS_MAX; i++)
		217	if (sem_table[i].used) {
		218	if (strcmp(name, sem_table[i].name) == 0) {
		219	found = 1;
		220	break;
		221	}
		222	}
		223	if (found) {
		224	if (oflag == (O_CREAT \| O_EXCL)) {
		225	errno = EEXIST;
		226	kern_sti();
		227	return SEM_FAILED;
		228	} else {
		229	kern_sti();
		230	return &sem_table[i].index;
		231	}
		232	} else {
		233	if (!(oflag & O_CREAT)) {
		234	errno = ENOENT;
		235	kern_sti();
		236	return SEM_FAILED;
		237	} else {
		238	va_list l;
		239
		240	va_start(l, oflag);
		241	m = va_arg(l,mode_t);
		242	j = va_arg(l, int);
		243	va_end(l);
		244
		245	if (j > SEM_VALUE_MAX) {
		246	errno = EINVAL;
		247	kern_sti();
		248	return SEM_FAILED;
		249	}
		250
		251	sem = free_sem;
		252	if (sem != -1) {
		253	free_sem = sem_table[sem].next;
		254	sem_table[sem].name = kern_alloc(strlen((char *)name)+1);
		255	strcpy(sem_table[sem].name, (char *)name);
		256	sem_table[sem].count = j;
29	pj	257	iq_init(&sem_table[sem].blocked, &freedesc, 0);
2	pj	258	sem_table[sem].used = 1;
		259	kern_sti();
		260	return &sem_table[sem].index;
		261	}
		262	else {
		263	errno = ENOSPC;
		264	kern_sti();
		265	return SEM_FAILED;
		266	}
		267	}
		268	}
		269	}
		270
		271	/----------------------------------------------------------------------/
		272	/* Frees a named semaphore */
		273	/----------------------------------------------------------------------/
		274	int sem_close(sem_t *sem)
		275	{
		276	kern_cli();
		277
		278	if (sem < 0 \|\| sem >= SEM_NSEMS_MAX \|\| !sem_table[*sem].used) {
		279	errno = EINVAL;
		280	kern_sti();
		281	return -1;
		282	}
		283
		284	/* why not???
		285	if (sem_table[*sem].q_first != -1) {
		286	errno = EBUSY;
		287	kern_sti();
		288	return -1;
		289	} */
		290
		291	kern_free(sem_table[sem].name,strlen(sem_table[sem].name)+1);
		292	sem_table[*sem].used = 0;
		293	sem_table[*sem].next = free_sem;
		294	free_sem = *sem;
		295
		296	kern_sti();
		297	return 0;
		298	}
		299
		300	/----------------------------------------------------------------------/
		301	/* Unlink a named semaphore */
		302	/----------------------------------------------------------------------/
		303	int sem_unlink(const char *name)
		304	{
		305	int i;
		306	int found = 0;
		307
		308	kern_cli();
		309
		310	for (i = 0; i < SEM_NSEMS_MAX; i++)
		311	if (sem_table[i].used) {
		312	if (strcmp(name, sem_table[i].name) == 0) {
		313	found = 1;
		314	}
		315	}
		316
		317	if (found) {
		318	kern_free(sem_table[i].name,strlen((char *)name)+1);
		319	sem_table[i].used = 0;
		320	sem_table[i].next = free_sem;
		321	free_sem = i;
		322	kern_sti();
		323	return 0;
		324	} else {
		325	errno = ENOENT;
		326	kern_sti();
		327	return SEM_FAILED;
		328	}
		329	}
		330
		331	/----------------------------------------------------------------------/
		332	/* Generic wait. If it is possible, decrements the sem counter of n, */
		333	/* else blocks the task. */
		334	/----------------------------------------------------------------------/
		335	int sem_wait(sem_t *s)
		336	{
		337	struct sem_des s1; / It speeds up access */
		338
		339	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		340	errno = EINVAL;
		341	return -1;
		342	}
		343
		344	task_testcancel();
		345
		346	proc_table[exec_shadow].context = kern_context_save();
		347
		348	s1 = &sem_table[*s];
		349
		350	if (s1->blocked.first != NIL \|\| s1->count == 0) {
		351	/* We must block exec task */
		352	LEVEL l; /* for readableness only */
		353
		354	/* tracer stuff */
		355	trc_logevent(TRC_SEM_WAIT,s);
		356
38	pj	357	kern_epilogue_macro();
		358
2	pj	359	l = proc_table[exec_shadow].task_level;
38	pj	360	level_table[l]->public_block(l,exec_shadow);
2	pj	361
		362	/* we insert the task in the semaphore queue */
		363	proc_table[exec_shadow].status = WAIT_SEM;
		364
		365	/* Prepare sem_table des... */
		366	sp_table[exec_shadow].decsem = 1;
		367	sp_table[exec_shadow].sem = *s;
		368
		369	/* ...and put it in sem queue */
29	pj	370	iq_insertlast(exec_shadow,&s1->blocked);
2	pj	371
		372	/* and finally we reschedule */
		373	exec = exec_shadow = -1;
		374	scheduler();
		375	kern_context_load(proc_table[exec_shadow].context);
		376
		377	/* sem_wait is a cancellation point... */
		378	task_testcancel();
		379	}
		380	else {
		381	s1->count--;
		382	/* tracer stuff */
		383	trc_logevent(TRC_SEM_WAIT,s);
		384	kern_context_load(proc_table[exec_shadow].context);
		385	}
		386
		387	return 0;
		388	}
		389
		390	/----------------------------------------------------------------------/
		391	/* Non-blocking wait */
		392	/----------------------------------------------------------------------/
		393	int sem_trywait(sem_t *s)
		394	{
		395	struct sem_des s1; / It speeds up access */
		396
		397	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		398	errno = EINVAL;
		399	return -1;
		400	}
		401
		402	kern_cli();
		403
		404	s1 = &sem_table[*s];
		405
		406	/* tracer stuff */
		407	//trc_logevent(TRC_SEM_WAITNB,s);
		408
		409	if (s1->blocked.first != NIL \|\| s1->count == 0) {
		410	errno = EAGAIN;
		411	kern_sti();
		412	return -1;
		413	}
		414	else
		415	s1->count--;
		416
		417	kern_sti();
		418	return 0;
		419	}
		420
		421
		422	/----------------------------------------------------------------------/
		423	/* Generic wait. If it is possible, decrements the sem counter of n, */
		424	/* else blocks the task. */
		425	/----------------------------------------------------------------------/
		426	int sem_xwait(sem_t *s, int n, int wait)
		427	{
		428	struct sem_des s1; / It speeds up access */
		429
		430	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		431	errno = EINVAL;
		432	return -1;
		433	}
		434
		435	/* We do not need to save context if we are sure we shall not block! */
		436	if (wait == NON_BLOCK)
		437	kern_cli();
		438	else
		439	proc_table[exec_shadow].context = kern_context_save();
		440
		441	s1 = &sem_table[*s];
		442
		443	/* The non blocking wait is really simple! */
		444	/* We do not suspend or schedule anything */
		445	if (wait == NON_BLOCK) {
		446	/* tracer */
		447	//trc_logevent(TRC_SEM_WAITNB,s);
		448
		449	if (s1->blocked.first != NIL \|\| s1->count < n) {
		450	errno = EAGAIN;
		451	kern_sti();
		452	return -1;
		453	}
		454	else
		455	s1->count -= n;
		456
		457	kern_sti();
		458	return 0;
		459	}
		460	/* The blocking wait is more complex... */
		461	else {
		462	/* the blocking wait is a cancellation point */
		463	task_testcancel();
		464
		465	if (s1->blocked.first != NIL \|\| s1->count < n) {
		466	/* We must block exec task */
		467	LEVEL l; /* for readableness only */
		468
		469	/* tracer */
		470	trc_logevent(TRC_SEM_WAIT,s);
38	pj	471
		472	kern_epilogue_macro();
2	pj	473
		474	l = proc_table[exec_shadow].task_level;
38	pj	475	level_table[l]->public_block(l,exec_shadow);
2	pj	476
		477	/* we insert the task in the semaphore queue */
		478	proc_table[exec_shadow].status = WAIT_SEM;
		479
		480	/* Prepare sem_table des... */
		481	sp_table[exec_shadow].decsem = n;
		482	sp_table[exec_shadow].sem = *s;
		483
		484	/* ...and put it in sem queue */
29	pj	485	iq_insertlast(exec_shadow,&s1->blocked);
2	pj	486
		487	/* and finally we reschedule */
		488	exec = exec_shadow = -1;
		489	scheduler();
		490	kern_context_load(proc_table[exec_shadow].context);
		491
		492	/* sem_wait is a cancellation point... */
		493	task_testcancel();
		494	}
		495	else {
		496	s1->count -= n;
		497	/* tracer */
		498	trc_logevent(TRC_SEM_WAIT,s);
		499	kern_context_load(proc_table[exec_shadow].context);
		500	}
		501	}
		502
		503	return 0;
		504	}
		505
		506	/----------------------------------------------------------------------/
		507	/* Generic signal. It increments the sem counter of 1, and wakes one */
		508	/* of the tasks that are blocked on the semaphore, if it is possible.The*/
		509	/* semaphoric queue is a FIFO queue, in order to eliminate deadlocks */
		510	/----------------------------------------------------------------------/
		511	int sem_post(sem_t *s)
		512	{
		513	struct sem_des s1; / it speeds up access */
		514	int p; /* idem */
		515	LEVEL l;
		516
		517	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		518	errno = EINVAL;
		519	return -1;
		520	}
		521
		522	// ugly patch to call a sem_post!!!
		523	if (ll_ActiveInt()) {
		524	SYS_FLAGS f;
		525	f = kern_fsave();
		526	s1 = &sem_table[*s];
		527	s1->count ++; /* inc sem count */
		528
		529	p = s1->blocked.first;
		530	if (p != NIL && sp_table[p].decsem <= s1->count) {
		531	/* Dec sem count */
		532	s1->count -= sp_table[p].decsem;
		533
		534	/* Get task from blocked queue */
29	pj	535	iq_extract(p,&s1->blocked);
2	pj	536
		537	l = proc_table[p].task_level;
38	pj	538	level_table[l]->public_unblock(l,p);
2	pj	539	/* only a task can be awaken */
		540	/* Preempt if necessary */
		541	event_need_reschedule();
		542	}
		543
		544	/* tracer */
		545	trc_logevent(TRC_SEM_SIGNAL,s);
		546	kern_frestore(f);
		547	}
		548	else {
		549	proc_table[exec].context = kern_context_save();
		550
		551	s1 = &sem_table[*s];
		552	s1->count ++; /* inc sem count */
		553
		554	p = s1->blocked.first;
		555	if (p != NIL && sp_table[p].decsem <= s1->count) {
		556	/* Dec sem count */
		557	s1->count -= sp_table[p].decsem;
		558
		559	/* Get task from blocked queue */
29	pj	560	iq_extract(p,&s1->blocked);
2	pj	561
		562	l = proc_table[p].task_level;
38	pj	563	level_table[l]->public_unblock(l,p);
2	pj	564	/* only a task can be awaken */
		565	/* Preempt if necessary */
		566	scheduler();
		567	}
		568
		569	/* tracer */
		570	trc_logevent(TRC_SEM_SIGNAL,s);
		571
		572	kern_context_load(proc_table[exec_shadow].context);
		573	}
		574
		575	return 0;
		576	}
		577
		578	/----------------------------------------------------------------------/
		579	/* Generic signal. It increments the sem counter of n, and wakes all the*/
		580	/* tasks that are blocked on the semaphore, if it is possible. The */
		581	/* semaphoric queue is a FIFO queue, in order to eliminate deadlocks */
		582	/----------------------------------------------------------------------/
		583	int sem_xpost(sem_t *s, int n)
		584	{
		585	struct sem_des s1; / it speeds up access */
		586	int p; /* idem */
		587	int fl = 0; /* a flag */
		588	LEVEL l;
		589
		590	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		591	errno = EINVAL;
		592	return -1;
		593	}
		594
		595	// ugly patch to call a sem_post!!!
		596	if (ll_ActiveInt()) {
		597	SYS_FLAGS f;
		598	f = kern_fsave();
		599	s1 = &sem_table[*s];
		600	s1->count += n; /* inc sem count */
		601
		602	p = s1->blocked.first;
		603	while (p != NIL && sp_table[p].decsem <= s1->count) {
		604	/* Dec sem count */
		605	s1->count -= sp_table[p].decsem;
		606
		607	/* Get task from blocked queue */
29	pj	608	iq_extract(p,&s1->blocked);
2	pj	609
		610	l = proc_table[p].task_level;
38	pj	611	level_table[l]->public_unblock(l,p);
2	pj	612
		613	/* Next task to wake */
		614	p = s1->blocked.first;
		615
		616	fl = 1;
		617	}
		618
		619	/* tracer */
		620	trc_logevent(TRC_SEM_SIGNAL,s);
		621
		622	/* Preempt if necessary */
		623	if (fl) event_need_reschedule();
		624	kern_frestore(f);
		625	}
		626	else {
		627	proc_table[exec].context = kern_context_save();
		628
		629	s1 = &sem_table[*s];
		630	s1->count += n; /* inc sem count */
		631
		632	p = s1->blocked.first;
		633	while (p != NIL && sp_table[p].decsem <= s1->count) {
		634	/* Dec sem count */
		635	s1->count -= sp_table[p].decsem;
		636
		637	/* Get task from blocked queue */
29	pj	638	iq_extract(p,&s1->blocked);
2	pj	639
		640	l = proc_table[p].task_level;
38	pj	641	level_table[l]->public_unblock(l,p);
2	pj	642
		643	/* Next task to wake */
		644	p = s1->blocked.first;
		645
		646	fl = 1;
		647	}
		648
		649	/* tracer */
		650	trc_logevent(TRC_SEM_SIGNAL,s);
		651
		652	/* Preempt if necessary */
		653	if (fl) scheduler();
		654
		655	kern_context_load(proc_table[exec_shadow].context);
		656	}
		657
		658	return 0;
		659	}
		660
		661	/----------------------------------------------------------------------/
		662	/* Getvalue returns the value of the semaphore (>=0). If someone is */
		663	/* blocked on the semaphore, return the number of process blocked (<0) */
		664	/----------------------------------------------------------------------/
		665	int sem_getvalue(sem_t sem, int sval)
		666	{
		667	PID p;
		668
		669	if (sem < 0 \|\| sem >= SEM_NSEMS_MAX \|\| !sem_table[*sem].used) {
		670	errno = EINVAL;
		671	return -1;
		672	}
		673
		674	kern_cli();
		675
29	pj	676	if (iq_isempty(&sem_table[*sem].blocked))
2	pj	677	/* the sem is free */
		678	sval = sem_table[sem].count;
		679	else {
		680	/* the sem is busy */
		681	*sval = 0;
29	pj	682	p = iq_query_first(&sem_table[*sem].blocked);
2	pj	683	do {
		684	(*sval)--;
29	pj	685	p = iq_query_next(p, &sem_table[*sem].blocked);
2	pj	686	} while (p != NIL);
		687	}
		688
		689	kern_sti();
		690	return 0;
		691	}
		692
		693
		694	/----------------------------------------------------------------------/
		695	/* this function returns 1 if the task is blocked on a semaphore */
		696	/----------------------------------------------------------------------/
		697	int isBlocked(PID i)
		698	{
		699	if (proc_table[i].status == WAIT_SEM) return 1;
		700	else return 0;
		701	}
		702

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(root)/shark/trunk/kernel/modules/sem.c - Rev 38