288 lines
11 KiB
C
288 lines
11 KiB
C
/* 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 WAITPID or WAIT system call
|
|
*/
|
|
|
|
|
|
#include "mm.h"
|
|
#include <sys/wait.h>
|
|
#include <minix/callnr.h>
|
|
#include <minix/com.h>
|
|
#include <minix/utils.h>
|
|
#include <signal.h>
|
|
#include "mproc.h"
|
|
#include "param.h"
|
|
|
|
#define LAST_FEW 2 /* last few slots reserved for superuser */
|
|
|
|
PRIVATE pid_t next_pid = INIT_PID+1; /* next pid to be assigned */
|
|
|
|
FORWARD _PROTOTYPE (void cleanup, (register struct mproc *child) );
|
|
|
|
/*===========================================================================*
|
|
* 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;
|
|
phys_clicks prog_clicks, child_base;
|
|
phys_bytes prog_bytes, parent_abs, child_abs; /* Intel only */
|
|
|
|
/* 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) ||
|
|
(procs_in_use >= NR_PROCS-LAST_FEW && rmp->mp_effuid != 0))
|
|
{
|
|
printf("MM: proc table full!\n");
|
|
return(EAGAIN);
|
|
}
|
|
|
|
/* Determine how much memory to allocate. Only the data and stack need to
|
|
* be copied, because the text segment is either shared or of zero length.
|
|
*/
|
|
prog_clicks = (phys_clicks) rmp->mp_seg[S].mem_len;
|
|
prog_clicks += (rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
|
|
prog_bytes = (phys_bytes) prog_clicks << CLICK_SHIFT;
|
|
if ( (child_base = alloc_mem(prog_clicks)) == NO_MEM) return(ENOMEM);
|
|
|
|
/* Create a copy of the parent's core image for the child. */
|
|
child_abs = (phys_bytes) child_base << CLICK_SHIFT;
|
|
parent_abs = (phys_bytes) rmp->mp_seg[D].mem_phys << CLICK_SHIFT;
|
|
i = sys_abscopy(parent_abs, child_abs, prog_bytes);
|
|
if (i < 0) panic("do_fork can't copy", i);
|
|
|
|
/* 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++;
|
|
*rmc = *rmp; /* copy parent's process slot to child's */
|
|
|
|
rmc->mp_parent = who; /* record child's parent */
|
|
rmc->mp_flags &= (IN_USE|SEPARATE); /* inherit only these flags */
|
|
|
|
/* A separate I&D child keeps the parents text segment. The data and stack
|
|
* segments must refer to the new copy.
|
|
*/
|
|
if (!(rmc->mp_flags & SEPARATE)) rmc->mp_seg[T].mem_phys = child_base;
|
|
rmc->mp_seg[D].mem_phys = child_base;
|
|
rmc->mp_seg[S].mem_phys = rmc->mp_seg[D].mem_phys +
|
|
(rmp->mp_seg[S].mem_vir - rmp->mp_seg[D].mem_vir);
|
|
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);
|
|
|
|
/* Tell kernel and file system about the (now successful) FORK. */
|
|
sys_fork(who, child_nr, rmc->mp_pid);
|
|
tell_fs(FORK, who, child_nr, rmc->mp_pid);
|
|
|
|
/* Report child's memory map to kernel. */
|
|
sys_newmap(child_nr, rmc->mp_seg);
|
|
|
|
/* Reply to child to wake it up. */
|
|
setreply(child_nr, 0);
|
|
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, m_in.status);
|
|
return(SUSPEND); /* can't communicate from beyond the grave */
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* 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. Release most of the process' possessions. If its
|
|
* parent is waiting, release the rest, else keep the process slot and
|
|
* become a zombie.
|
|
*/
|
|
|
|
register int proc_nr;
|
|
int parent_waiting, right_child;
|
|
pid_t pidarg, procgrp;
|
|
struct mproc *p_mp;
|
|
|
|
proc_nr = (int) (rmp - mproc); /* get process slot number */
|
|
|
|
/* Remember a session leader's process group. */
|
|
procgrp = (rmp->mp_pid == mp->mp_procgrp) ? mp->mp_procgrp : 0;
|
|
|
|
/* If the exited process has a timer pending, kill it. */
|
|
if (rmp->mp_flags & ALARM_ON) set_alarm(proc_nr, (unsigned) 0);
|
|
|
|
/* Tell the kernel and FS that the process is no longer runnable. */
|
|
tell_fs(EXIT, proc_nr, 0, 0); /* file system can free the proc slot */
|
|
sys_xit(rmp->mp_parent, proc_nr);
|
|
|
|
/* Release the memory occupied by the child. */
|
|
if (find_share(rmp, rmp->mp_ino, rmp->mp_dev, rmp->mp_ctime) == NULL) {
|
|
/* No other process shares the text segment, so free it. */
|
|
free_mem(rmp->mp_seg[T].mem_phys, rmp->mp_seg[T].mem_len);
|
|
}
|
|
/* Free the data and stack segments. */
|
|
free_mem(rmp->mp_seg[D].mem_phys,
|
|
rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len - rmp->mp_seg[D].mem_vir);
|
|
|
|
/* The process slot can only be freed if the parent has done a WAIT. */
|
|
rmp->mp_exitstatus = (char) exit_status;
|
|
|
|
p_mp = &mproc[rmp->mp_parent]; /* process' parent */
|
|
pidarg = p_mp->mp_wpid; /* who's being waited for? */
|
|
parent_waiting = p_mp->mp_flags & WAITING;
|
|
|
|
right_child = /* child meets one of the 3 tests? */
|
|
(pidarg == -1 || pidarg == rmp->mp_pid || -pidarg == rmp->mp_procgrp);
|
|
|
|
if (parent_waiting && right_child) {
|
|
cleanup(rmp); /* tell parent and release child slot */
|
|
} else {
|
|
rmp->mp_flags = IN_USE|ZOMBIE; /* parent not waiting, zombify child */
|
|
sig_proc(p_mp, SIGCHLD); /* send parent a "child died" signal */
|
|
}
|
|
|
|
/* If the process has children, disinherit them. INIT is the new parent. */
|
|
for (rmp = &mproc[0]; rmp < &mproc[NR_PROCS]; rmp++) {
|
|
if (rmp->mp_flags & IN_USE && rmp->mp_parent == proc_nr) {
|
|
/* 'rmp' now points to a child to be disinherited. */
|
|
rmp->mp_parent = INIT_PROC_NR;
|
|
parent_waiting = mproc[INIT_PROC_NR].mp_flags & WAITING;
|
|
if (parent_waiting && (rmp->mp_flags & ZOMBIE)) cleanup(rmp);
|
|
}
|
|
}
|
|
|
|
/* Send a hangup to the process' process group if it was a session leader. */
|
|
if (procgrp != 0) check_sig(-procgrp, SIGHUP);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* do_waitpid *
|
|
*===========================================================================*/
|
|
PUBLIC int do_waitpid()
|
|
{
|
|
/* 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.
|
|
* Both WAIT and WAITPID are handled by this code.
|
|
*/
|
|
|
|
register struct mproc *rp;
|
|
int pidarg, options, children;
|
|
|
|
/* A process calling WAIT never gets a reply in the usual way at the end
|
|
* of the main loop (unless WNOHANG is set or no qualifying child exists).
|
|
* If a child has already exited, the routine cleanup() sends the reply
|
|
* to awaken the caller.
|
|
*/
|
|
|
|
/* Set internal variables, depending on whether this is WAIT or WAITPID. */
|
|
pidarg = (call_nr == WAIT ? -1 : m_in.pid); /* 1st param of waitpid */
|
|
options = (call_nr == WAIT ? 0 : m_in.sig_nr); /* 3rd param of waitpid */
|
|
if (pidarg == 0) pidarg = -mp->mp_procgrp; /* pidarg < 0 ==> proc grp */
|
|
|
|
/* Is there a child waiting to be collected? At this point, pidarg != 0:
|
|
* pidarg > 0 means pidarg is pid of a specific process to wait for
|
|
* pidarg == -1 means wait for any child
|
|
* pidarg < -1 means wait for any child whose process group = -pidarg
|
|
*/
|
|
children = 0;
|
|
for (rp = &mproc[0]; rp < &mproc[NR_PROCS]; rp++) {
|
|
if ( (rp->mp_flags & IN_USE) && rp->mp_parent == who) {
|
|
/* The value of pidarg determines which children qualify. */
|
|
if (pidarg > 0 && pidarg != rp->mp_pid) continue;
|
|
if (pidarg < -1 && -pidarg != rp->mp_procgrp) continue;
|
|
|
|
children++; /* this child is acceptable */
|
|
if (rp->mp_flags & ZOMBIE) {
|
|
/* This child meets the pid test and has exited. */
|
|
cleanup(rp); /* this child has already exited */
|
|
return(SUSPEND);
|
|
}
|
|
if ((rp->mp_flags & STOPPED) && rp->mp_sigstatus) {
|
|
/* This child meets the pid test and is being traced.*/
|
|
mp->mp_reply.reply_res2 = 0177|(rp->mp_sigstatus << 8);
|
|
rp->mp_sigstatus = 0;
|
|
return(rp->mp_pid);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* No qualifying child has exited. Wait for one, unless none exists. */
|
|
if (children > 0) {
|
|
/* At least 1 child meets the pid test exists, but has not exited. */
|
|
if (options & WNOHANG) return(0); /* parent does not want to wait */
|
|
mp->mp_flags |= WAITING; /* parent wants to wait */
|
|
mp->mp_wpid = (pid_t) pidarg; /* save pid for later */
|
|
return(SUSPEND); /* do not reply, let it wait */
|
|
} else {
|
|
/* No child even meets the pid test. Return error immediately. */
|
|
return(ECHILD); /* no - parent has no children */
|
|
}
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* cleanup *
|
|
*===========================================================================*/
|
|
PRIVATE void cleanup(child)
|
|
register struct mproc *child; /* tells which process is exiting */
|
|
{
|
|
/* Finish off the exit of a process. The process has exited or been killed
|
|
* by a signal, and its parent is waiting.
|
|
*/
|
|
|
|
struct mproc *parent = &mproc[child->mp_parent];
|
|
int exitstatus;
|
|
|
|
/* Wake up the parent. */
|
|
exitstatus = (child->mp_exitstatus << 8) | (child->mp_sigstatus & 0377);
|
|
parent->mp_reply.reply_res2 = exitstatus;
|
|
setreply(child->mp_parent, child->mp_pid);
|
|
parent->mp_flags &= ~WAITING; /* parent no longer waiting */
|
|
|
|
/* Release the process table entry. */
|
|
child->mp_flags = 0;
|
|
procs_in_use--;
|
|
}
|