do_exit.c

Minix3.11的源码。[MINIX 3是一个为高可靠性应用而设计的自由且简洁的类UNIX系统。]

/* The kernel call implemented in this file:
 *   m_type:	SYS_EXIT
 *
 * The parameters for this kernel call are:
 *    m1_i1:	PR_PROC_NR		(slot number of exiting process)
 */

#include "../system.h"

#if USE_EXIT

FORWARD _PROTOTYPE( void clear_proc, (register struct proc *rc));

/*===========================================================================*
 *				do_exit					     *
 *===========================================================================*/
PUBLIC int do_exit(m_ptr)
message *m_ptr;			/* pointer to request message */
{
/* Handle sys_exit. A user process has exited or a system process requests 
 * to exit. Only the PM can request other process slots to be cleared.
 * The routine to clean up a process table slot cancels outstanding timers, 
 * possibly removes the process from the message queues, and resets certain 
 * process table fields to the default values.
 */
  int exit_proc_nr;				

  /* Determine what process exited. User processes are handled here. */
  if (PM_PROC_NR == m_ptr->m_source) {
      exit_proc_nr = m_ptr->PR_PROC_NR;		/* get exiting process */
      if (exit_proc_nr != SELF) { 		/* PM tries to exit self */
          if (! isokprocn(exit_proc_nr)) return(EINVAL);
          clear_proc(proc_addr(exit_proc_nr));	/* exit a user process */
          return(OK);				/* report back to PM */
      }
  } 

  /* The PM or some other system process requested to be exited. */
  clear_proc(proc_addr(m_ptr->m_source));
  return(EDONTREPLY);
}

/*===========================================================================*
 *			         clear_proc				     *
 *===========================================================================*/
PRIVATE void clear_proc(rc)
register struct proc *rc;		/* slot of process to clean up */
{
  register struct proc *rp;		/* iterate over process table */
  register struct proc **xpp;		/* iterate over caller queue */
  int i;
  int sys_id;
  char saved_rts_flags;

  /* Don't clear if already cleared. */
  if(isemptyp(rc)) return;

  /* Turn off any alarm timers at the clock. */   
  reset_timer(&priv(rc)->s_alarm_timer);

  /* Make sure that the exiting process is no longer scheduled. */
  if (rc->p_rts_flags == 0) lock_dequeue(rc);

  /* Release the process table slot. If this is a system process, also
   * release its privilege structure.  Further cleanup is not needed at
   * this point. All important fields are reinitialized when the 
   * slots are assigned to another, new process. 
   */
  saved_rts_flags = rc->p_rts_flags;
  rc->p_rts_flags = SLOT_FREE;		
  if (priv(rc)->s_flags & SYS_PROC) priv(rc)->s_proc_nr = NONE;

  /* If the process being terminated happens to be queued trying to send a
   * message (e.g., the process was killed by a signal, rather than it doing 
   * a normal exit), then it must be removed from the message queues.
   */
  if (saved_rts_flags & SENDING) {
      xpp = &proc[rc->p_sendto].p_caller_q;	/* destination's queue */
      while (*xpp != NIL_PROC) {		/* check entire queue */
          if (*xpp == rc) {			/* process is on the queue */
              *xpp = (*xpp)->p_q_link;		/* replace by next process */
#if DEBUG_ENABLE_IPC_WARNINGS
	      kprintf("Proc %d removed from queue at %d\n",
	          proc_nr(rc), rc->p_sendto);
#endif
              break;				/* can only be queued once */
          }
          xpp = &(*xpp)->p_q_link;		/* proceed to next queued */
      }
  }

  /* Likewise, if another process was sending or receive a message to or from 
   * the exiting process, it must be alerted that process no longer is alive.
   * Check all processes. 
   */
  for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; rp++) {
      if(isemptyp(rp))
	continue;

      /* Unset pending notification bits. */
      unset_sys_bit(priv(rp)->s_notify_pending, priv(rc)->s_id);

      /* Check if process is receiving from exiting process. */
      if ((rp->p_rts_flags & RECEIVING) && rp->p_getfrom == proc_nr(rc)) {
          rp->p_reg.retreg = ESRCDIED;		/* report source died */
	  rp->p_rts_flags &= ~RECEIVING;	/* no longer receiving */
#if DEBUG_ENABLE_IPC_WARNINGS
	  kprintf("Proc %d receive dead src %d\n", proc_nr(rp), proc_nr(rc));
#endif
  	  if (rp->p_rts_flags == 0) lock_enqueue(rp);/* let process run again */
      } 
      if ((rp->p_rts_flags & SENDING) && rp->p_sendto == proc_nr(rc)) {
          rp->p_reg.retreg = EDSTDIED;		/* report destination died */
	  rp->p_rts_flags &= ~SENDING;		/* no longer sending */
#if DEBUG_ENABLE_IPC_WARNINGS
	  kprintf("Proc %d send dead dst %d\n", proc_nr(rp), proc_nr(rc));
#endif
  	  if (rp->p_rts_flags == 0) lock_enqueue(rp);/* let process run again */
      } 
  }

  /* Check the table with IRQ hooks to see if hooks should be released. */
  for (i=0; i < NR_IRQ_HOOKS; i++) {
      if (irq_hooks[i].proc_nr == proc_nr(rc)) {
          rm_irq_handler(&irq_hooks[i]);	/* remove interrupt handler */
          irq_hooks[i].proc_nr = NONE; 		/* mark hook as free */
      }
  }
}

#endif /* USE_EXIT */