fix jobc adjustments so we increment before decrementing, avoiding spurious

[unix-history] / usr / src / sys / kern / kern_proc.c

/*
 * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)kern_proc.c	7.12 (Berkeley) %G%
 */

#include "param.h"
#include "systm.h"
#include "map.h"
#include "user.h"
#include "kernel.h"
#include "proc.h"
#include "buf.h"
#include "seg.h"
#include "acct.h"
#include "wait.h"
#include "vm.h"
#include "text.h"
#include "file.h"
#include "../ufs/quota.h"
#include "uio.h"
#include "malloc.h"
#include "mbuf.h"
#include "ioctl.h"
#include "tty.h"

#include "machine/reg.h"
#include "machine/pte.h"
#include "machine/psl.h"

/*
 * Is p an inferior of the current process?
 */
inferior(p)
	register struct proc *p;
{

	for (; p != u.u_procp; p = p->p_pptr)
		if (p->p_ppid == 0)
			return (0);
	return (1);
}

/*
 * Locate a process by number
 */
struct proc *
pfind(pid)
	register pid;
{
	register struct proc *p = pidhash[PIDHASH(pid)];

	for (; p; p = p->p_hash)
		if (p->p_pid == pid)
			return (p);
	return ((struct proc *)0);
}

/*
 * Locate a process group by number
 */
struct pgrp *
pgfind(pgid)
	register pid_t pgid;
{
	register struct pgrp *pgrp = pgrphash[PIDHASH(pgid)];

	for (; pgrp; pgrp = pgrp->pg_hforw)
		if (pgrp->pg_id == pgid)
			return (pgrp);
	return ((struct pgrp *)0);
}

/*
 * Move p to a new or existing process group (and session)
 */
pgmv(p, pgid, mksess)
	register struct proc *p;
	pid_t pgid;
{
	register struct pgrp *pgrp = pgfind(pgid);
	register struct proc **pp;
	register struct proc *cp;
	int n;

#ifdef DIAGNOSTIC
	if (pgrp && mksess)	/* firewalls */
		panic("pgmv: setsid into non-empty pgrp");
	if (SESS_LEADER(p))
		panic("pgmv: session leader attempted setpgrp");
#endif
	if (pgrp == NULL) {
		/*
		 * new process group
		 */
#ifdef DIAGNOSTIC
		if (p->p_pid != pgid)
			panic("pgmv: new pgrp and pid != pgid");
#endif
		MALLOC(pgrp, struct pgrp *, sizeof(struct pgrp), M_PGRP,
		       M_WAITOK);
		if (mksess) {
			register struct session *sess;
			/*
			 * new session
			 */
			MALLOC(sess, struct session *, sizeof(struct session),
				M_SESSION, M_WAITOK);
			sess->s_leader = p;
			sess->s_count = 1;
			sess->s_ttyvp = NULL;
			sess->s_ttyp = NULL;
			p->p_flag &= ~SCTTY;
			pgrp->pg_session = sess;
#ifdef DIAGNOSTIC
			if (p != u.u_procp)
				panic("pgmv: mksession and p != u.u_procp");
#endif
		} else {
			pgrp->pg_session = p->p_session;
			pgrp->pg_session->s_count++;
		}
		pgrp->pg_id = pgid;
		pgrp->pg_hforw = pgrphash[n = PIDHASH(pgid)];
		pgrphash[n] = pgrp;
		pgrp->pg_jobc = 0;
		pgrp->pg_mem = NULL;
	} else if (pgrp == p->p_pgrp)
		return;

	/*
	 * Adjust eligibility of affected pgrps to participate in job control.
	 * Increment eligibility counts before decrementing, otherwise we
	 * could reach 0 spuriously during the first call.
	 */
	fixjobc(p, pgrp, 1);
	fixjobc(p, p->p_pgrp, 0);

	/*
	 * unlink p from old process group
	 */
	for (pp = &p->p_pgrp->pg_mem; *pp; pp = &(*pp)->p_pgrpnxt)
		if (*pp == p) {
			*pp = p->p_pgrpnxt;
			goto done;
		}
	panic("pgmv: can't find p on old pgrp");
done:
	/*
	 * delete old if empty
	 */
	if (p->p_pgrp->pg_mem == 0)
		pgdelete(p->p_pgrp);
	/*
	 * link into new one
	 */
	p->p_pgrp = pgrp;
	p->p_pgrpnxt = pgrp->pg_mem;
	pgrp->pg_mem = p;
}

/*
 * remove process from process group
 */
pgrm(p)
	register struct proc *p;
{
	register struct proc **pp = &p->p_pgrp->pg_mem;

	for (; *pp; pp = &(*pp)->p_pgrpnxt)
		if (*pp == p) {
			*pp = p->p_pgrpnxt;
			goto done;
		}
	panic("pgrm: can't find p in pgrp");
done:
	if (!p->p_pgrp->pg_mem)
		pgdelete(p->p_pgrp);
	p->p_pgrp = 0;
}

/*
 * delete a process group
 */
pgdelete(pgrp)
	register struct pgrp *pgrp;
{
	register struct pgrp **pgp = &pgrphash[PIDHASH(pgrp->pg_id)];

	if (pgrp->pg_session->s_ttyp != NULL && 
	    pgrp->pg_session->s_ttyp->t_pgrp == pgrp)
		pgrp->pg_session->s_ttyp->t_pgrp = NULL;
	for (; *pgp; pgp = &(*pgp)->pg_hforw)
		if (*pgp == pgrp) {
			*pgp = pgrp->pg_hforw;
			goto done;
		}
	panic("pgdelete: can't find pgrp on hash chain");
done:
	if (--pgrp->pg_session->s_count == 0)
		FREE(pgrp->pg_session, M_SESSION);
	FREE(pgrp, M_PGRP);
}

/*
 * Adjust pgrp jobc counters when specified process changes process group.
 * We count the number of processes in each process group that "qualify"
 * the group for terminal job control (those with a parent in a different
 * process group of the same session).  If that count reaches zero, the
 * process group becomes orphaned.  Check both the specified process'
 * process group and that of its children.
 * entering == 0 => p is leaving specified group.
 * entering == 1 => p is entering specified group.
 */
fixjobc(p, pgrp, entering)
	register struct proc *p;
	register struct pgrp *pgrp;
	int entering;
{
	register struct pgrp *hispgrp;
	register struct session *mysession = pgrp->pg_session;

	/*
	 * Check p's parent to see whether p qualifies its own process
	 * group; if so, adjust count for p's process group.
	 */
	if ((hispgrp = p->p_pptr->p_pgrp) != pgrp &&
	    hispgrp->pg_session == mysession)
		if (entering)
			pgrp->pg_jobc++;
		else if (--pgrp->pg_jobc == 0)
			orphanpg(pgrp);

	/*
	 * Check this process' children to see whether they qualify
	 * their process groups; if so, adjust counts for children's
	 * process groups.
	 */
	for (p = p->p_cptr; p; p = p->p_osptr)
		if ((hispgrp = p->p_pgrp) != pgrp &&
		    hispgrp->pg_session == mysession &&
		    p->p_stat != SZOMB)
			if (entering)
				hispgrp->pg_jobc++;
			else if (--hispgrp->pg_jobc == 0)
				orphanpg(hispgrp);
}

/* 
 * A process group has become orphaned;
 * if there are any stopped processes in the group,
 * hang-up all process in that group.
 */
static
orphanpg(pg)
	struct pgrp *pg;
{
	register struct proc *p;

	for (p = pg->pg_mem; p; p = p->p_pgrpnxt) {
		if (p->p_stat == SSTOP) {
			for (p = pg->pg_mem; p; p = p->p_pgrpnxt) {
				psignal(p, SIGHUP);
				psignal(p, SIGCONT);
			}
			return;
		}
	}
}

/*
 * init the process queues
 */
pqinit()
{
	register struct proc *p;

	/*
	 * most procs are initially on freequeue
	 *	nb: we place them there in their "natural" order.
	 */

	freeproc = NULL;
	for (p = procNPROC; --p > proc; freeproc = p)
		p->p_nxt = freeproc;

	/*
	 * but proc[0] is special ...
	 */

	allproc = p;
	p->p_nxt = NULL;
	p->p_prev = &allproc;

	zombproc = NULL;
}

#ifdef debug
/* DEBUG */
pgrpdump()
{
	register struct pgrp *pgrp;
	register struct proc *p;
	register i;

	for (i=0; i<PIDHSZ; i++) {
		if (pgrphash[i]) {
		  printf("\tindx %d\n", i);
		  for (pgrp=pgrphash[i]; pgrp; pgrp=pgrp->pg_hforw) {
		    printf("\tpgrp %x, pgid %d, sess %x, sesscnt %d, mem %x\n",
			pgrp, pgrp->pg_id, pgrp->pg_session,
			pgrp->pg_session->s_count, pgrp->pg_mem);
		    for (p=pgrp->pg_mem; p; p=p->p_pgrpnxt) {
			printf("\t\tpid %d addr %x pgrp %x\n", 
				p->p_pid, p, p->p_pgrp);
		    }
		  }

		}
	}
}
#endif /* debug */