tm.c

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/*
 *  The contents of this file are subject to the Mozilla Public License
 *  Version 1.0 (the "License"); you may not use this file except in
 *  compliance with the License. You may obtain a copy of the License at
 *  http://www.mozilla.org/MPL/
 *
 *  Software distributed under the License is distributed on an "AS IS"
 *  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 *  License for the specific language governing rights and limitations
 *  under the License.
 *
 *  The Original Code is legOS code, released October 17, 1999.
 *
 *  The Initial Developer of the Original Code is Markus L. Noga.
 *  Portions created by Markus L. Noga are Copyright (C) 1999
 *  Markus L. Noga. All Rights Reserved.
 *
 *  Contributor(s): Markus L. Noga <markus@noga.de>
 *                  Ben Laurie <ben@algroup.co.uk>
 *                  Lou Sortman <lou (at) sunsite (dot) unc (dot) edu>
 */

#include <sys/tm.h>

#ifdef CONF_TM

#include <sys/critsec.h>
#include <sys/mm.h>
#include <sys/time.h>
#include <sys/irq.h>
#include <sys/bitops.h>
#include <stdlib.h>
#include <unistd.h>

#ifdef CONF_VIS
# include <sys/lcd.h>
# include <conio.h>
# include <sys/battery.h>
#endif

#define fatal(a)
// #define fatal(a)  { lcd_clear(); cputs(a); lcd_refresh(); while(1); }

//
// Variables
//

pchain_t *priority_head;                        

tdata_t td_single;                              
tdata_t *ctid;                                  

volatile unsigned int nb_tasks;                 
volatile unsigned int nb_system_tasks;          

//
// Functions
//

#if 0
void integrity_check(void) {
  pchain_t *prio=priority_head;
  tdata_t *td;
  
  if(prio->prev!=NULL) {  fatal("ERR10");  }
  
  do {
    if(prio->next) {
      if(prio->next->prev!=prio) { fatal("ERR11"); }
      if(prio->next->priority>prio->priority) { fatal("ERR12"); }
    }
    td=prio->ctid;
    do {
      if(td==NULL) { fatal("ERR13"); }
      if(td->priority!=prio) { fatal("ERR14"); }
      if(td->next->prev != td) { fatal("ERR15"); }
      if(td->prev->next != td) { fatal("ERR16"); }
      
      td=td->next;
    } while(td!=prio->ctid);
    
    prio=prio->next;
  } while(prio);
} 
#endif 
    


void tm_switcher(void);
#ifndef DOXYGEN_SHOULD_SKIP_THIS
__asm__("\n\
.text\n\
.align 1\n\
.globl _tm_switcher\n\
_tm_switcher:\n\
      ; r6 saved by ROM\n\
      ; r0 saved by system timer handler\n\
\n\
      mov.w r1,@-r7                           ; save registers\n\
      mov.w r2,@-r7 \n\
      mov.w r3,@-r7 \n\
      mov.w r4,@-r7 \n\
      mov.w r5,@-r7 \n\
\n\
      mov.w r7,r0                             ; pass sp\n\
\n\
      jsr _tm_scheduler                       ; call scheduler\n\
\n\
_tm_switcher_return:    \n\
      mov.w r0,r7                             ; set new sp\n\
\n\
      mov.w @r7+,r5\n\
      mov.w @r7+,r4\n\
      mov.w @r7+,r3\n\
      mov.w @r7+,r2\n\
      mov.w @r7+,r1\n\
\n\
      ; r0 will be restored by system timer handler\n\
      ; r6 will be restored by ROM\n\
\n\
      rts                                     ; return to new task\n\
");
#endif  // DOXYGEN_SHOULD_SKIP_THIS



size_t *tm_scheduler(size_t *old_sp) {
  tdata_t  *next;                             // next task to execute
  pchain_t *priority;
  wakeup_t tmp;

  priority=ctid->priority;
  switch(ctid->tstate) {
  case T_ZOMBIE:
    if(ctid->next!=ctid) {
      // remove from chain for this priority level
      //

      priority->ctid  =ctid->prev;
      ctid->next->prev=ctid->prev;
      ctid->prev->next=ctid->next;
    } else {
      // remove priority chain for this priority level
      //

      if(priority->next)
        priority->next->prev = priority->prev;
      if(priority->prev)
        priority->prev->next = priority->next;
      else
        priority_head = priority->next;
      free(priority);
    }
      
    // We're on that stack frame being freed right now,
    // but nobody can interrupt us anyways.
    //
    free(ctid->stack_base);                   // free stack
    free(ctid);                               // free task data

    //
    // FIXME: exit code?
    //

    if ((ctid->tflags & T_KERNEL)==T_KERNEL)
      --nb_system_tasks;

    switch(--nb_tasks) {
    case 1:
#ifdef CONF_TM_DEBUG    
      if((priority_head->ctid->tflags & T_IDLE)==0) {
        // last task is not the idle task
        fatal("ERR00");
      }
#endif // CONF_TM_DEBUG
      // only the idle task remains
      *((priority_head->ctid->sp_save) + SP_RETURN_OFFSET ) = (size_t) &exit;
      priority_head->ctid->tstate=T_SLEEPING;
      break;
    
    case 0:
      // the last task has been removed
      // -> stop switcher, go single tasking
    
      systime_set_switcher(&rom_dummy_handler);
      ctid=&td_single;
    
      return ctid->sp_save;
    }
    break;

  case T_RUNNING:
    ctid->tstate=T_SLEEPING;
    // no break

  case T_WAITING:
    ctid->sp_save=old_sp;
  }


  // find next task willing to run
  //  
  priority=priority_head;
  next=priority->ctid->next;
  while (1) {
    if (next->tstate==T_SLEEPING)
      break;
    
    if (next->tstate==T_WAITING) {
      if ((next->tflags & T_SHUTDOWN) != 0) {
        next->wakeup_data = 0;
        break;
      }
      ctid = next;
      tmp = next->wakeup(next->wakeup_data);
      if (tmp != 0) {
        next->wakeup_data = tmp;
        break;
      }
    }
    
    if(next == priority->ctid) {
      // if we've scanned the whole chain,
      // go to next priority
      
      if(priority->next != NULL) 
        priority = priority->next;
#ifdef CONF_TM_DEBUG        
      else {
        // FIXME: idle task has died
        //        this is a severe error.
        fatal("ERR01");
      }
#else
      else
        priority = priority_head;
#endif
      next=priority->ctid->next;
    } else
      next=next->next;
  }
  ctid=next->priority->ctid=next;             // execute next task
  ctid->tstate=T_RUNNING;

  return ctid->sp_save;
}


extern void yield(void);
#ifndef DOXYGEN_SHOULD_SKIP_THIS
__asm__("\n\
.text\n\
.globl _yield\n\
.align 1\n\
_yield:\n\
      stc     ccr,r0h                ; to fake an IRQ, we have to\n\
      push    r0                     ; store the registers\n\
      orc     #0x80,ccr              ; disable interrupts\n\
\n\
      push    r6                     ; store r6\n\
\n\
      mov.w   #0x04d4,r0             ; store rom return addr\n\
      push    r0\n\
\n\
      push    r0                     ; store r0 (destroyed by call.)\n\
\n\
      mov.w   #_systime_tm_return,r0 ; store systime return addr\n\
      push    r0\n\
\n\
      jmp     @_tm_switcher          ; call task switcher\n\
");
#endif  // DOXYGEN_SHOULD_SKIP_THIS


extern int tm_idle_task(int argc,char **argv) __attribute__ ((noreturn));
#ifndef DOXYGEN_SHOULD_SKIP_THIS
__asm__("\n\
.text\n\
.align 1\n\
_tm_idle_task:\n\
      sleep\n\
      bra _tm_idle_task\n\
");
#endif  // DOXYGEN_SHOULD_SKIP_THIS

#ifdef CONF_VIS


int tm_man_task(int argc, char **argv)
{
  int state=0;

  while (!shutdown_requested()) {
    if(nb_tasks > nb_system_tasks) state ^= 1; else state=0;
    lcd_show(state == 0 ? man_stand : man_run);
#ifndef CONF_LCD_REFRESH
    lcd_refresh();
#endif // CONF_LCD_REFRESH
    msleep(500);
  }
  return 0;
}

#ifdef CONF_BATTERY_INDICATOR


int tm_battery_task(int argc, char **argv) {
  int bmv;

  while (!shutdown_requested()) {
    bmv=get_battery_mv();

    if(bmv>BATTERY_NORMAL_THRESHOLD_MV)
      dlcd_hide(LCD_BATTERY_X);
    else if(bmv<BATTERY_LOW_THRESHOLD_MV)
      dlcd_show(LCD_BATTERY_X);

    msleep(2000);
  }
  return 0;
}
#endif // CONF_BATTERY_INDICATOR
#endif // CONF_VIS


void tm_init(void) {
  tdata_t* td_idle;

  // no tasks right now.
  //
  nb_tasks=0;
  nb_system_tasks=0;
  priority_head=NULL;
  INITIALIZE_KERNEL_CRITICAL_SECTION(); 
 
  // the single tasking context
  //
  td_single.tstate=T_RUNNING;
  ctid=&td_single;

  // the idle task is an institution
  //  
  td_idle=(tdata_t*)execi(&tm_idle_task,0,NULL,0,IDLE_STACK_SIZE);
  td_idle->tflags |= T_IDLE;

#ifdef CONF_VIS
  execi(&tm_man_task, 0, NULL, 1, IDLE_STACK_SIZE);

#ifdef CONF_BATTERY_INDICATOR
  execi(&tm_battery_task, 0, NULL, 1, IDLE_STACK_SIZE);
#endif // CONF_BATTERY_INDICATOR
#endif // CONF_VIS

  systime_set_timeslice(TM_DEFAULT_SLICE);
} 



void tm_start(void) {
  disable_irqs();                               // no interruptions, please

  systime_set_switcher(&tm_switcher);
  yield();                                      // go!

  enable_irqs();                                // restored state would 
                                                // disallow interrupts
}


tid_t execi(int (*code_start)(int,char**),int argc, char **argv,
            priority_t priority,size_t stack_size) {
  pchain_t *pchain, *ppchain; // for traversing priority chain
  int freepchain=0;
  
  // get memory
  //
  // task & stack area belong to parent task
  // they aren't freed by mm_reaper()
  //
  // avoid deadlock of memory and task semaphores
  // by preallocation.
  
  tdata_t *td=malloc(sizeof(tdata_t));
  size_t *sp=malloc(stack_size);
  
  // for allocating new priority chain
  pchain_t *newpchain=malloc(sizeof(pchain_t));

  if (td == NULL || sp == NULL || newpchain == NULL)
  {
    free(td);
    free(sp);
    free(newpchain);
    return -1;
  }
  
  td->tflags = 0;
  if ((size_t)code_start < (size_t)&mm_start)
  {
    td->tflags |= T_KERNEL;
    nb_system_tasks++;
  }
  else
    td->tflags |= T_USER;

  td->stack_base=sp;                  // these we know already.

  sp+=(stack_size>>1);                // setup initial stack

  // when main() returns a value, it passes it in r0
  // as r0 is also the register to pass single int arguments by
  // gcc convention, we can just put the address of exit on the stack.

  *(--sp)=(size_t) &exit;

  // we have to construct a stack stub so tm_switcher,
  // systime_handler and the ROM routine can fill the 
  // right values on startup.

  *(--sp)=(size_t) code_start;        // entry point   < these two are for
  *(--sp)=0;                          // ccr           < rte in ROM
  *(--sp)=0;                          // r6      < pop r6 in ROM
  *(--sp)=(size_t)
          &rom_ocia_return;         // ROM return < rts in systime_handler

  *(--sp)=(size_t) argc;              // r0     < pop r0 in systime handler
  *(--sp)=(size_t)              
          &systime_tm_return;       // systime return < rts in tm_switcher

  *(--sp)=(size_t) argv;              // r1..r5 < pop r1..r5 in tm_switcher
  *(--sp)=0;
  *(--sp)=0;
  *(--sp)=0;
  *(--sp)=0;

  td->sp_save=sp;                   // save sp for tm_switcher
  td->tstate=T_SLEEPING;              // task is waiting for execution
  td->parent=ctid;                    // set parent

  ENTER_KERNEL_CRITICAL_SECTION();

  ppchain=NULL;
  for(  pchain = priority_head;
    pchain != NULL && (pchain->priority) > priority;
    ppchain = pchain, pchain = pchain->next
  );
  if(pchain==NULL || pchain->priority!=priority) {
    // make new chain
    //
    newpchain->priority=priority;
    newpchain->ctid=td;

    newpchain->next=pchain;
    if(pchain)
      pchain->prev =newpchain;
    newpchain->prev=ppchain;
    if(ppchain)
      ppchain->next=newpchain;
    else
      priority_head=newpchain;

    // initial queue setup
    //
    td->prev=td->next=td;
    td->priority=newpchain;
  } else {
    // add at back of queue
    //
    td->priority=pchain;
    td->prev=pchain->ctid->prev;
    td->next=pchain->ctid;
    td->next->prev=td->prev->next=td;
    freepchain=1; // free superfluous pchain.
  }
  nb_tasks++;

  LEAVE_KERNEL_CRITICAL_SECTION();  

  if(freepchain)
    free(newpchain);
  
  return (tid_t) td;                  // tid = (tid_t) &tdata_t_struct
}


void exit(int code) {
  enable_irqs();                                // just in case...
  if (!(ctid->tflags & T_KERNEL))
    mm_reaper();
  ctid->tstate=T_ZOMBIE;
  // Yield till dead
  while(1)
    yield();
}


wakeup_t wait_event(wakeup_t (*wakeup)(wakeup_t),wakeup_t data) {
  ctid->wakeup     =wakeup;
  ctid->wakeup_data=data;
  ctid->tstate     =T_WAITING;

  yield();

  return ctid->wakeup_data;
}


static wakeup_t tm_sleep_wakeup(wakeup_t data) {
  time_t remaining = ((time_t)data) - get_system_up_time();

  if (((time_t)data) <= get_system_up_time())
  {
    tm_timeslice = TM_DEFAULT_SLICE;
    return -1;
  }

  if (remaining < tm_timeslice)
    tm_timeslice = remaining;

  return 0;
}


unsigned int msleep(unsigned int msec)
{
#if defined(CONF_TIME) && defined(CONF_TM)
  if (wait_event(&tm_sleep_wakeup, get_system_up_time() + MSECS_TO_TICKS(msec)) == 0)
    return (MSECS_TO_TICKS(msec) - get_system_up_time());
#else
  delay(msec);
#endif
  return 0;
}


unsigned int sleep(unsigned int sec)
{
  return msleep(1000*sec)/1000;
}


void shutdown_task(tid_t tid) {
  tdata_t *td=(tdata_t*) tid;
  td->tflags |= T_SHUTDOWN;
}


void shutdown_tasks(tflags_t flags) {
  pchain_t* pchain;
  tdata_t* td;

  ENTER_KERNEL_CRITICAL_SECTION();  
 
  pchain = priority_head;
  while (pchain != NULL) {
    td = pchain->ctid;
    do {
      if ((td->tflags & flags) != 0) {
        // signal shutdown
        //
        td->tflags |= T_SHUTDOWN;
      }
      td = td->next;
    } while (td != pchain->ctid);
    pchain = pchain->next;
  }
 
  LEAVE_KERNEL_CRITICAL_SECTION();
}


void kill(tid_t tid) {
  tdata_t *td=(tdata_t*) tid;
  if(td==ctid)
    exit(-1);
  else {
    // when the task is switched to the next time,
    // make it exit immediatlely.

    ENTER_KERNEL_CRITICAL_SECTION(); 

    *( (td->sp_save) + SP_RETURN_OFFSET )=(size_t) &exit;
    td->tstate=T_SLEEPING;    // in case it's waiting.

    LEAVE_KERNEL_CRITICAL_SECTION();
  }
}


void killall(priority_t prio) {
  pchain_t *pchain;
  tdata_t *td;
  tflags_t flags = T_KERNEL | T_IDLE;
  
  if (prio == PRIO_HIGHEST)
    flags = T_IDLE;

  ENTER_KERNEL_CRITICAL_SECTION();

  // find first chain with smaller or equal priority.
  //
  pchain=priority_head;
  while(pchain!=NULL && prio<pchain->priority)
    pchain=pchain->next;

  while(pchain!=NULL) {
    td=pchain->ctid;
    do {
      if((td!=ctid) && ((td->tflags & flags) == 0)) {
        // kill it
        //
        *( (td->sp_save) + SP_RETURN_OFFSET )=(size_t) &exit;
        td->tstate=T_SLEEPING;    // in case it's waiting.
      }
      td=td->next;
    } while(td!=pchain->ctid);
    pchain=pchain->next;
  }  

  LEAVE_KERNEL_CRITICAL_SECTION();
}

#endif // CONF_TM

---