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/*
* Project: S.Ha.R.K.
*
* Coordinators:
* Giorgio Buttazzo <giorgio@sssup.it>
* Paolo Gai <pj@gandalf.sssup.it>
*
* Authors :
* Paolo Gai <pj@gandalf.sssup.it>
* (see the web pages for full authors list)
*
* ReTiS Lab (Scuola Superiore S.Anna - Pisa - Italy)
*
* http://www.sssup.it
* http://retis.sssup.it
* http://shark.sssup.it
*/
/**
------------
CVS : $Id: int_sem.c,v 1.1.1.1 2002-03-29 14:12:51 pj Exp $
File: $File$
Revision: $Revision: 1.1.1.1 $
Last update: $Date: 2002-03-29 14:12:51 $
------------
Internal semaphores.
They are different from the Posix semaphores and the mutexes because:
- internal_sem_wait is not a cancellation point
- there are no limits on the semaphores that can be created
(they works like a mutex_t...)
- the queuing policy is FIFO
- Be Careful!
they are made to be fast... so not so many controls are done!!!
**/
/*
* Copyright (C) 2000 Paolo Gai
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <kernel/int_sem.h>
#include <kernel/var.h>
#include <kernel/func.h>
/* Wait status for this library */
#define INTERNAL_SEM_WAIT LIB_STATUS_BASE
void internal_sem_init(internal_sem_t *s, int value)
{
s->count = value;
qq_init(&s->blocked);
}
void internal_sem_wait(internal_sem_t *s)
{
SYS_FLAGS f;
//kern_cli();
f = kern_fsave();
if (s->count) {
s->count--;
//kern_sti();
kern_frestore(f);
return;
}
else { /* We must block exec task */
LEVEL l; /* for readableness only */
TIME tx; /* a dummy TIME for timespec operations */
struct timespec ty; /* a dummy timespec for timespec operations */
proc_table[exec_shadow].context = kern_context_save();
/* SAME AS SCHEDULER... manage the capacity event and the load_info */
ll_gettime(TIME_EXACT, &schedule_time);
SUBTIMESPEC(&schedule_time, &cap_lasttime, &ty);
tx = TIMESPEC2USEC(&ty);
proc_table[exec_shadow].avail_time -= tx;
jet_update_slice(tx);
if (cap_timer != NIL) {
event_delete(cap_timer);
cap_timer = NIL;
}
l = proc_table[exec_shadow].task_level;
level_table[l]->task_extract(l,exec_shadow);
/* we insert the task in the semaphore queue */
proc_table[exec_shadow].status = INTERNAL_SEM_WAIT;
qq_insertlast(exec_shadow,&s->blocked);
/* and finally we reschedule */
exec = exec_shadow = -1;
scheduler();
ll_context_to(proc_table[exec_shadow].context);
kern_after_dispatch();
kern_frestore(f);
}
}
/* return 0 if the counter is decremented, -1 if not */
int internal_sem_trywait(internal_sem_t *s)
{
SYS_FLAGS f;
//kern_cli();
f = kern_fsave();
if (s->count) {
s->count--;
//kern_sti();
kern_frestore(f);
return 0;
}
//kern_sti();
kern_frestore(f);
return -1;
}
void internal_sem_post(internal_sem_t *s)
{
proc_table[exec_shadow].context = kern_context_save();
if (s->blocked.first != -1) {
register PID p;
register LEVEL l;
p = qq_getfirst(&s->blocked);
l = proc_table[p].task_level;
level_table[l]->task_insert(l,p);
scheduler();
}
else
s->count++;
kern_context_load(proc_table[exec_shadow].context);
}
int internal_sem_getvalue(internal_sem_t *s)
{
register int returnvalue;
SYS_FLAGS f;
//kern_cli();
f = kern_fsave();
if (s->blocked.first == -1)
returnvalue = s->count;
else
returnvalue = -1;
//kern_sti();
kern_frestore(f);
return returnvalue;
}