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Atari Mega Archive 2
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mm
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forkexit.c
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C/C++ Source or Header
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1990-07-15
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10KB
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292 lines
/* This file deals with creating processes (via FORK) and deleting them (via
* EXIT/WAIT). When a process forks, a new slot in the 'mproc' table is
* allocated for it, and a copy of the parent's core image is made for the
* child. Then the kernel and file system are informed. A process is removed
* from the 'mproc' table when two events have occurred: (1) it has exited or
* been killed by a signal, and (2) the parent has done a WAIT. If the process
* exits first, it continues to occupy a slot until the parent does a WAIT.
*
* The entry points into this file are:
* do_fork: perform the FORK system call
* do_mm_exit: perform the EXIT system call (by calling mm_exit())
* mm_exit: actually do the exiting
* do_wait: perform the WAIT system call
*/
#include "mm.h"
#include <minix/callnr.h>
#include "mproc.h"
#include "param.h"
#define LAST_FEW 2 /* last few slots reserved for superuser */
PRIVATE next_pid = INIT_PID+1; /* next pid to be assigned */
FORWARD void cleanup();
/*===========================================================================*
* do_fork *
*===========================================================================*/
PUBLIC int do_fork()
{
/* The process pointed to by 'mp' has forked. Create a child process. */
register struct mproc *rmp; /* pointer to parent */
register struct mproc *rmc; /* pointer to child */
int i, child_nr, t;
char *sptr, *dptr;
phys_clicks prog_clicks, child_base;
#if (CHIP == INTEL)
long prog_bytes;
long parent_abs, child_abs;
#endif
/* If tables might fill up during FORK, don't even start since recovery half
* way through is such a nuisance.
*/
rmp = mp;
if (procs_in_use == NR_PROCS) return(EAGAIN);
if (procs_in_use >= NR_PROCS - LAST_FEW && rmp->mp_effuid != 0)return(EAGAIN);
/* Determine how much memory to allocate. */
prog_clicks = (phys_clicks) rmp->mp_seg[S].mem_len;
prog_clicks += (rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
#if (CHIP == INTEL)
if (rmp->mp_flags & SEPARATE) prog_clicks += rmp->mp_seg[T].mem_len;
prog_bytes = (long) prog_clicks << CLICK_SHIFT;
#endif
if ( (child_base = alloc_mem(prog_clicks)) == NO_MEM) return(EAGAIN);
#if (CHIP == INTEL)
/* Create a copy of the parent's core image for the child. */
child_abs = (long) child_base << CLICK_SHIFT;
parent_abs = (long) rmp->mp_seg[T].mem_phys << CLICK_SHIFT;
i = mem_copy(ABS, 0, parent_abs, ABS, 0, child_abs, prog_bytes);
if ( i < 0) panic("do_fork can't copy", i);
#endif
/* Find a slot in 'mproc' for the child process. A slot must exist. */
for (rmc = &mproc[0]; rmc < &mproc[NR_PROCS]; rmc++)
if ( (rmc->mp_flags & IN_USE) == 0) break;
/* Set up the child and its memory map; copy its 'mproc' slot from parent. */
child_nr = (int)(rmc - mproc); /* slot number of the child */
procs_in_use++;
sptr = (char *) rmp; /* pointer to parent's 'mproc' slot */
dptr = (char *) rmc; /* pointer to child's 'mproc' slot */
i = sizeof(struct mproc); /* number of bytes in a proc slot. */
while (i--) *dptr++ = *sptr++;/* copy from parent slot to child's */
rmc->mp_parent = who; /* record child's parent */
rmc->mp_flags &= ~TRACED; /* child does not inherit trace status */
#if (CHIP == INTEL)
rmc->mp_seg[T].mem_phys = child_base;
rmc->mp_seg[D].mem_phys = child_base + rmc->mp_seg[T].mem_len;
rmc->mp_seg[S].mem_phys = rmc->mp_seg[D].mem_phys +
(rmp->mp_seg[S].mem_phys - rmp->mp_seg[D].mem_phys);
#endif
rmc->mp_exitstatus = 0;
rmc->mp_sigstatus = 0;
/* Find a free pid for the child and put it in the table. */
do {
t = 0; /* 't' = 0 means pid still free */
next_pid = (next_pid < 30000 ? next_pid + 1 : INIT_PID + 1);
for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++)
if (rmp->mp_pid == next_pid || rmp->mp_procgrp == next_pid) {
t = 1;
break;
}
rmc->mp_pid = next_pid; /* assign pid to child */
} while (t);
/* Set process group. */
if (who == INIT_PROC_NR) rmc->mp_procgrp = rmc->mp_pid;
/* Tell kernel and file system about the (now successful) FORK. */
#if (CHIP == M68000)
sys_fork(who, child_nr, rmc->mp_pid, child_base);
#else
sys_fork(who, child_nr, rmc->mp_pid);
#endif
tell_fs(FORK, who, child_nr, rmc->mp_pid);
#if (CHIP == INTEL)
/* Report child's memory map to kernel. */
sys_newmap(child_nr, rmc->mp_seg);
#endif
/* Reply to child to wake it up. */
reply(child_nr, 0, 0, NIL_PTR);
return(next_pid); /* child's pid */
}
/*===========================================================================*
* do_mm_exit *
*===========================================================================*/
PUBLIC int do_mm_exit()
{
/* Perform the exit(status) system call. The real work is done by mm_exit(),
* which is also called when a process is killed by a signal.
*/
mm_exit(mp, status);
dont_reply = TRUE; /* don't reply to newly terminated process */
return(OK); /* pro forma return code */
}
/*===========================================================================*
* mm_exit *
*===========================================================================*/
PUBLIC void mm_exit(rmp, exit_status)
register struct mproc *rmp; /* pointer to the process to be terminated */
int exit_status; /* the process' exit status (for parent) */
{
/* A process is done. If parent is waiting for it, clean it up, else hang. */
#if (CHIP == M68000)
phys_clicks base, size;
#else
phys_clicks s;
#endif
register int proc_nr = (int)(rmp - mproc);
/* How to terminate a process is determined by whether or not the
* parent process has already done a WAIT. Test to see if it has.
*/
rmp->mp_exitstatus = (char) exit_status; /* store status in 'mproc' */
if (mproc[rmp->mp_parent].mp_flags & WAITING)
cleanup(rmp); /* release parent and tell everybody */
else
rmp->mp_flags |= HANGING; /* Parent not waiting. Suspend proc */
/* If the exited process has a timer pending, kill it. */
if (rmp->mp_flags & ALARM_ON) set_alarm(proc_nr, (unsigned) 0);
#if AM_KERNEL
/* see if an amoeba transaction was pending or a putrep needed to be done */
am_check_sig(proc_nr, 1);
#endif
/* Tell the kernel and FS that the process is no longer runnable. */
#if (CHIP == M68000)
sys_xit(rmp->mp_parent, proc_nr, &base, &size);
free_mem(base, size);
#else
sys_xit(rmp->mp_parent, proc_nr);
#endif
tell_fs(EXIT, proc_nr, 0, 0); /* file system can free the proc slot */
#if (CHIP == INTEL)
/* Release the memory occupied by the child. */
s = (phys_clicks) rmp->mp_seg[S].mem_len;
s += (rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
if (rmp->mp_flags & SEPARATE) s += rmp->mp_seg[T].mem_len;
free_mem(rmp->mp_seg[T].mem_phys, s); /* free the memory */
#endif
}
/*===========================================================================*
* do_wait *
*===========================================================================*/
PUBLIC int do_wait()
{
/* A process wants to wait for a child to terminate. If one is already waiting,
* go clean it up and let this WAIT call terminate. Otherwise, really wait.
*/
register struct mproc *rp;
register int children;
/* A process calling WAIT never gets a reply in the usual way via the
* reply() in the main loop. If a child has already exited, the routine
* cleanup() sends the reply to awaken the caller.
*/
/* Is there a child waiting to be collected? */
children = 0;
for (rp = &mproc[0]; rp < &mproc[NR_PROCS]; rp++) {
if ( (rp->mp_flags & IN_USE) && rp->mp_parent == who) {
children++;
if (rp->mp_flags & HANGING) {
cleanup(rp); /* a child has already exited */
dont_reply = TRUE;
return(OK);
}
if (rp->mp_flags & STOPPED && rp->mp_sigstatus) {
reply(who, rp->mp_pid, 0177 | (rp->mp_sigstatus << 8),
NIL_PTR);
dont_reply = TRUE;
rp->mp_sigstatus = 0;
return(OK);
}
}
}
/* No child has exited. Wait for one, unless none exists. */
if (children > 0) { /* does this process have any children? */
mp->mp_flags |= WAITING;
dont_reply = TRUE;
return(OK); /* yes - wait for one to exit */
} else
return(ECHILD); /