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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>

 *   Massimiliano Giorgi <massy@gandalf.sssup.it>

 *   Luca Abeni          <luca@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: nop.c,v 1.3 2003-01-07 17:07:50 pj Exp $

 File:        $File$

 Revision:    $Revision: 1.3 $

 Last update: $Date: 2003-01-07 17:07:50 $

 ------------

 Binary Semaphores. see nop.h for more details...

**/

/*

 * 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 <modules/nop.h>

#include <ll/ll.h>

#include <ll/stdio.h>

#include <ll/string.h>

#include <kernel/const.h>

#include <sys/types.h>

#include <kernel/descr.h>

#include <kernel/var.h>

#include <kernel/func.h>

/* The NOP resource level descriptor */

typedef struct {

  mutex_resource_des m;   /*+ the mutex interface +*/

} NOP_mutex_resource_des;

/* this is the structure normally pointed by the opt field in the

   mutex_t structure */

typedef struct {

  PID owner;

  IQUEUE blocked;

} NOP_mutex_t;

/* Wait status for this library */

#define NOP_WAIT LIB_STATUS_BASE

static int NOP_res_register(RLEVEL l, PID p, RES_MODEL *r)

{

  return -1;

}

static void NOP_res_detach(RLEVEL l, PID p)

{

}

static int NOP_init(RLEVEL l, mutex_t *m, const mutexattr_t *a)

{

  NOP_mutex_t *p;

  if (a->mclass != NOP_MCLASS)

    return -1;

  p = (NOP_mutex_t *) kern_alloc(sizeof(NOP_mutex_t));

  /* control if there is enough memory; no control on init on a

     non- destroyed mutex */

  if (!p)

    return (ENOMEM);

  p->owner = NIL;

  iq_init(&p->blocked, &freedesc, 0);

  m->mutexlevel = l;

  m->opt = (void *)p;

  return 0;

}

static int NOP_destroy(RLEVEL l, mutex_t *m)

{

//  NOP_mutex_resource_des *lev = (NOP_mutex_resource_des *)(resource_table[l]);

  if ( ((NOP_mutex_t *)m->opt)->owner != NIL)

    return (EBUSY);

  kern_cli();

  if (m->opt) {

    kern_free(m->opt,sizeof(NOP_mutex_t));

    m->opt = NULL;

  }

  kern_sti();

  return 0;

}

static int NOP_lock(RLEVEL l, mutex_t *m)

{

  NOP_mutex_t *p;

  kern_cli();

  p = (NOP_mutex_t *)m->opt;

  if (!p) {

    /* if the mutex is not initialized, initialize it! */

    NOP_mutexattr_t a;

    NOP_mutexattr_default(a);

    NOP_init(l, m, &a);

  }

  if (p->owner == exec_shadow) {

    /* the task already owns the mutex */

    kern_sti();

    return (EDEADLK);

  }

  if (p->owner != NIL)  {           /* We must block exec task   */

       LEVEL l;            /* for readableness only */

       proc_table[exec_shadow].context = kern_context_save();

       kern_epilogue_macro();

       l = proc_table[exec_shadow].task_level;

       level_table[l]->public_block(l,exec_shadow);

       /* we insert the task in the semaphore queue */

       proc_table[exec_shadow].status = NOP_WAIT;

       iq_insertlast(exec_shadow,&p->blocked);

       /* and finally we reschedule */

       exec = exec_shadow = -1;

       scheduler();

       kern_context_load(proc_table[exec_shadow].context);

  }

  else {

    /* the mutex is free, We can lock it! */

    p->owner = exec_shadow;

    kern_sti();

  }

  return 0;

}

static int NOP_trylock(RLEVEL l, mutex_t *m)

{

  NOP_mutex_t *p;

  kern_cli();

  p = (NOP_mutex_t *)m->opt;

  if (!p) {

    /* if the mutex is not initialized, initialize it! */

    NOP_mutexattr_t a;

    NOP_mutexattr_default(a);

    NOP_init(l, m, &a);

  }

  if (p->owner != NIL)  {

    /* a task already owns the mutex */

    kern_sti();

    return (EBUSY);

  }

  else {

    /* the mutex is free, We can lock it! */

    p->owner = exec_shadow;

    kern_sti();

  }

  return 0;

}

static int NOP_unlock(RLEVEL l, mutex_t *m)

{

  NOP_mutex_t *p;

  p = (NOP_mutex_t *)m->opt;

  if (!p)

    return (EINVAL);

  if (p->owner != exec_shadow) {

    /* the mutex is owned by another task!!! */

    kern_sti();

    return (EPERM);

  }

  proc_table[exec_shadow].context = kern_context_save();

  /* the mutex is mine, pop the firsttask to extract */

  p->owner = iq_getfirst(&p->blocked);

  if (p->owner != NIL) {

    l = proc_table[p->owner].task_level;

    level_table[l]->public_unblock(l,p->owner);

  }

  scheduler();

  kern_context_load(proc_table[exec_shadow].context);

  return 0;

}

RLEVEL NOP_register_module(void)

{

  RLEVEL l;                  /* the level that we register */

  NOP_mutex_resource_des *m;  /* for readableness only */

  printk("NOP_register_module\n");

  /* request an entry in the level_table */

  l = resource_alloc_descriptor();

  /* alloc the space needed for the EDF_level_des */

  m = (NOP_mutex_resource_des *)kern_alloc(sizeof(NOP_mutex_resource_des));

  /* update the level_table with the new entry */

  resource_table[l] = (resource_des *)m;

  /* fill the resource_des descriptor */

  m->m.r.rtype                       = MUTEX_RTYPE;

  m->m.r.res_register                = NOP_res_register;

  m->m.r.res_detach                  = NOP_res_detach;

  /* fill the mutex_resource_des descriptor */

  m->m.init                          = NOP_init;

  m->m.destroy                       = NOP_destroy;

  m->m.lock                          = NOP_lock;

  m->m.trylock                       = NOP_trylock;

  m->m.unlock                        = NOP_unlock;

  return l;

}