WebSVN - shark - Blame - Rev 29 - /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	------------
29	pj	23	CVS : $Id: sem.c,v 1.2 2002-11-11 08:32:07 pj Exp $
2	pj	24
		25	File: $File$
29	pj	26	Revision: $Revision: 1.2 $
		27	Last update: $Date: 2002-11-11 08:32:07 $
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;
		118	level_table[l]->task_insert(l,i);
		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	TIME tx; /* a dummy TIME for timespec operations */
		354	struct timespec ty; /* a dummy timespec for timespec operations */
		355
		356	/* tracer stuff */
		357	trc_logevent(TRC_SEM_WAIT,s);
		358
		359	/* SAME AS SCHEDULER... manage the capacity event and the load_info */
		360	ll_gettime(TIME_EXACT, &schedule_time);
		361	SUBTIMESPEC(&schedule_time, &cap_lasttime, &ty);
		362	tx = TIMESPEC2USEC(&ty);
		363	proc_table[exec_shadow].avail_time -= tx;
		364	jet_update_slice(tx);
		365	if (cap_timer != NIL) {
		366	event_delete(cap_timer);
		367	cap_timer = NIL;
		368	}
		369
		370	l = proc_table[exec_shadow].task_level;
		371	level_table[l]->task_extract(l,exec_shadow);
		372
		373	/* we insert the task in the semaphore queue */
		374	proc_table[exec_shadow].status = WAIT_SEM;
		375
		376	/* Prepare sem_table des... */
		377	sp_table[exec_shadow].decsem = 1;
		378	sp_table[exec_shadow].sem = *s;
		379
		380	/* ...and put it in sem queue */
29	pj	381	iq_insertlast(exec_shadow,&s1->blocked);
2	pj	382
		383	/* and finally we reschedule */
		384	exec = exec_shadow = -1;
		385	scheduler();
		386	kern_context_load(proc_table[exec_shadow].context);
		387
		388	/* sem_wait is a cancellation point... */
		389	task_testcancel();
		390	}
		391	else {
		392	s1->count--;
		393	/* tracer stuff */
		394	trc_logevent(TRC_SEM_WAIT,s);
		395	kern_context_load(proc_table[exec_shadow].context);
		396	}
		397
		398	return 0;
		399	}
		400
		401	/----------------------------------------------------------------------/
		402	/* Non-blocking wait */
		403	/----------------------------------------------------------------------/
		404	int sem_trywait(sem_t *s)
		405	{
		406	struct sem_des s1; / It speeds up access */
		407
		408	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		409	errno = EINVAL;
		410	return -1;
		411	}
		412
		413	kern_cli();
		414
		415	s1 = &sem_table[*s];
		416
		417	/* tracer stuff */
		418	//trc_logevent(TRC_SEM_WAITNB,s);
		419
		420	if (s1->blocked.first != NIL \|\| s1->count == 0) {
		421	errno = EAGAIN;
		422	kern_sti();
		423	return -1;
		424	}
		425	else
		426	s1->count--;
		427
		428	kern_sti();
		429	return 0;
		430	}
		431
		432
		433	/----------------------------------------------------------------------/
		434	/* Generic wait. If it is possible, decrements the sem counter of n, */
		435	/* else blocks the task. */
		436	/----------------------------------------------------------------------/
		437	int sem_xwait(sem_t *s, int n, int wait)
		438	{
		439	struct sem_des s1; / It speeds up access */
		440
		441	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		442	errno = EINVAL;
		443	return -1;
		444	}
		445
		446	/* We do not need to save context if we are sure we shall not block! */
		447	if (wait == NON_BLOCK)
		448	kern_cli();
		449	else
		450	proc_table[exec_shadow].context = kern_context_save();
		451
		452	s1 = &sem_table[*s];
		453
		454	/* The non blocking wait is really simple! */
		455	/* We do not suspend or schedule anything */
		456	if (wait == NON_BLOCK) {
		457	/* tracer */
		458	//trc_logevent(TRC_SEM_WAITNB,s);
		459
		460	if (s1->blocked.first != NIL \|\| s1->count < n) {
		461	errno = EAGAIN;
		462	kern_sti();
		463	return -1;
		464	}
		465	else
		466	s1->count -= n;
		467
		468	kern_sti();
		469	return 0;
		470	}
		471	/* The blocking wait is more complex... */
		472	else {
		473	/* the blocking wait is a cancellation point */
		474	task_testcancel();
		475
		476	if (s1->blocked.first != NIL \|\| s1->count < n) {
		477	/* We must block exec task */
		478	LEVEL l; /* for readableness only */
		479	TIME tx; /* a dummy TIME for timespec operations */
		480	struct timespec ty; /* a dummy timespec for timespec operations */
		481
		482	/* tracer */
		483	trc_logevent(TRC_SEM_WAIT,s);
		484
		485	/* SAME AS SCHEDULER... manage the capacity event and the load_info */
		486	ll_gettime(TIME_EXACT, &schedule_time);
		487	SUBTIMESPEC(&schedule_time, &cap_lasttime, &ty);
		488	tx = TIMESPEC2USEC(&ty);
		489	proc_table[exec_shadow].avail_time -= tx;
		490	jet_update_slice(tx);
		491	if (cap_timer != NIL) {
		492	event_delete(cap_timer);
		493	cap_timer = NIL;
		494	}
		495
		496	l = proc_table[exec_shadow].task_level;
		497	level_table[l]->task_extract(l,exec_shadow);
		498
		499	/* we insert the task in the semaphore queue */
		500	proc_table[exec_shadow].status = WAIT_SEM;
		501
		502	/* Prepare sem_table des... */
		503	sp_table[exec_shadow].decsem = n;
		504	sp_table[exec_shadow].sem = *s;
		505
		506	/* ...and put it in sem queue */
29	pj	507	iq_insertlast(exec_shadow,&s1->blocked);
2	pj	508
		509	/* and finally we reschedule */
		510	exec = exec_shadow = -1;
		511	scheduler();
		512	kern_context_load(proc_table[exec_shadow].context);
		513
		514	/* sem_wait is a cancellation point... */
		515	task_testcancel();
		516	}
		517	else {
		518	s1->count -= n;
		519	/* tracer */
		520	trc_logevent(TRC_SEM_WAIT,s);
		521	kern_context_load(proc_table[exec_shadow].context);
		522	}
		523	}
		524
		525	return 0;
		526	}
		527
		528	/----------------------------------------------------------------------/
		529	/* Generic signal. It increments the sem counter of 1, and wakes one */
		530	/* of the tasks that are blocked on the semaphore, if it is possible.The*/
		531	/* semaphoric queue is a FIFO queue, in order to eliminate deadlocks */
		532	/----------------------------------------------------------------------/
		533	int sem_post(sem_t *s)
		534	{
		535	struct sem_des s1; / it speeds up access */
		536	int p; /* idem */
		537	LEVEL l;
		538
		539	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		540	errno = EINVAL;
		541	return -1;
		542	}
		543
		544	// ugly patch to call a sem_post!!!
		545	if (ll_ActiveInt()) {
		546	SYS_FLAGS f;
		547	f = kern_fsave();
		548	s1 = &sem_table[*s];
		549	s1->count ++; /* inc sem count */
		550
		551	p = s1->blocked.first;
		552	if (p != NIL && sp_table[p].decsem <= s1->count) {
		553	/* Dec sem count */
		554	s1->count -= sp_table[p].decsem;
		555
		556	/* Get task from blocked queue */
29	pj	557	iq_extract(p,&s1->blocked);
2	pj	558
		559	l = proc_table[p].task_level;
		560	level_table[l]->task_insert(l,p);
		561	/* only a task can be awaken */
		562	/* Preempt if necessary */
		563	event_need_reschedule();
		564	}
		565
		566	/* tracer */
		567	trc_logevent(TRC_SEM_SIGNAL,s);
		568	kern_frestore(f);
		569	}
		570	else {
		571	proc_table[exec].context = kern_context_save();
		572
		573	s1 = &sem_table[*s];
		574	s1->count ++; /* inc sem count */
		575
		576	p = s1->blocked.first;
		577	if (p != NIL && sp_table[p].decsem <= s1->count) {
		578	/* Dec sem count */
		579	s1->count -= sp_table[p].decsem;
		580
		581	/* Get task from blocked queue */
29	pj	582	iq_extract(p,&s1->blocked);
2	pj	583
		584	l = proc_table[p].task_level;
		585	level_table[l]->task_insert(l,p);
		586	/* only a task can be awaken */
		587	/* Preempt if necessary */
		588	scheduler();
		589	}
		590
		591	/* tracer */
		592	trc_logevent(TRC_SEM_SIGNAL,s);
		593
		594	kern_context_load(proc_table[exec_shadow].context);
		595	}
		596
		597	return 0;
		598	}
		599
		600	/----------------------------------------------------------------------/
		601	/* Generic signal. It increments the sem counter of n, and wakes all the*/
		602	/* tasks that are blocked on the semaphore, if it is possible. The */
		603	/* semaphoric queue is a FIFO queue, in order to eliminate deadlocks */
		604	/----------------------------------------------------------------------/
		605	int sem_xpost(sem_t *s, int n)
		606	{
		607	struct sem_des s1; / it speeds up access */
		608	int p; /* idem */
		609	int fl = 0; /* a flag */
		610	LEVEL l;
		611
		612	if (s < 0 \|\| s >= SEM_NSEMS_MAX \|\| !sem_table[*s].used) {
		613	errno = EINVAL;
		614	return -1;
		615	}
		616
		617	// ugly patch to call a sem_post!!!
		618	if (ll_ActiveInt()) {
		619	SYS_FLAGS f;
		620	f = kern_fsave();
		621	s1 = &sem_table[*s];
		622	s1->count += n; /* inc sem count */
		623
		624	p = s1->blocked.first;
		625	while (p != NIL && sp_table[p].decsem <= s1->count) {
		626	/* Dec sem count */
		627	s1->count -= sp_table[p].decsem;
		628
		629	/* Get task from blocked queue */
29	pj	630	iq_extract(p,&s1->blocked);
2	pj	631
		632	l = proc_table[p].task_level;
		633	level_table[l]->task_insert(l,p);
		634
		635	/* Next task to wake */
		636	p = s1->blocked.first;
		637
		638	fl = 1;
		639	}
		640
		641	/* tracer */
		642	trc_logevent(TRC_SEM_SIGNAL,s);
		643
		644	/* Preempt if necessary */
		645	if (fl) event_need_reschedule();
		646	kern_frestore(f);
		647	}
		648	else {
		649	proc_table[exec].context = kern_context_save();
		650
		651	s1 = &sem_table[*s];
		652	s1->count += n; /* inc sem count */
		653
		654	p = s1->blocked.first;
		655	while (p != NIL && sp_table[p].decsem <= s1->count) {
		656	/* Dec sem count */
		657	s1->count -= sp_table[p].decsem;
		658
		659	/* Get task from blocked queue */
29	pj	660	iq_extract(p,&s1->blocked);
2	pj	661
		662	l = proc_table[p].task_level;
		663	level_table[l]->task_insert(l,p);
		664
		665	/* Next task to wake */
		666	p = s1->blocked.first;
		667
		668	fl = 1;
		669	}
		670
		671	/* tracer */
		672	trc_logevent(TRC_SEM_SIGNAL,s);
		673
		674	/* Preempt if necessary */
		675	if (fl) scheduler();
		676
		677	kern_context_load(proc_table[exec_shadow].context);
		678	}
		679
		680	return 0;
		681	}
		682
		683	/----------------------------------------------------------------------/
		684	/* Getvalue returns the value of the semaphore (>=0). If someone is */
		685	/* blocked on the semaphore, return the number of process blocked (<0) */
		686	/----------------------------------------------------------------------/
		687	int sem_getvalue(sem_t sem, int sval)
		688	{
		689	PID p;
		690
		691	if (sem < 0 \|\| sem >= SEM_NSEMS_MAX \|\| !sem_table[*sem].used) {
		692	errno = EINVAL;
		693	return -1;
		694	}
		695
		696	kern_cli();
		697
29	pj	698	if (iq_isempty(&sem_table[*sem].blocked))
2	pj	699	/* the sem is free */
		700	sval = sem_table[sem].count;
		701	else {
		702	/* the sem is busy */
		703	*sval = 0;
29	pj	704	p = iq_query_first(&sem_table[*sem].blocked);
2	pj	705	do {
		706	(*sval)--;
29	pj	707	p = iq_query_next(p, &sem_table[*sem].blocked);
2	pj	708	} while (p != NIL);
		709	}
		710
		711	kern_sti();
		712	return 0;
		713	}
		714
		715
		716	/----------------------------------------------------------------------/
		717	/* this function returns 1 if the task is blocked on a semaphore */
		718	/----------------------------------------------------------------------/
		719	int isBlocked(PID i)
		720	{
		721	if (proc_table[i].status == WAIT_SEM) return 1;
		722	else return 0;
		723	}
		724

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(root)/shark/trunk/kernel/modules/sem.c - Rev 29