in fork1(), only add make the new proc visible (by giving it a pid
and adding it to allproc) after it's fully initialized. this prevents the scheduler from coming in via a clock interrupt and tripping over a partially-initialized proc.
This commit is contained in:
chs
parent
b7192d086c
commit
a284236c04
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@ -1,4 +1,4 @@
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/* $NetBSD: kern_fork.c,v 1.75 2000/11/07 12:41:52 jdolecek Exp $ */
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/* $NetBSD: kern_fork.c,v 1.76 2000/11/08 05:16:23 chs Exp $ */
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/*
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* Copyright (c) 1982, 1986, 1989, 1991, 1993
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@ -106,9 +106,8 @@ fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
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void (*func)(void *), void *arg, register_t *retval,
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struct proc **rnewprocp)
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{
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struct proc *p2;
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struct proc *p2, *tp;
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uid_t uid;
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struct proc *newproc;
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int count, s;
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vaddr_t uaddr;
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static int nextpid, pidchecked = 0;
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@ -126,6 +125,7 @@ fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
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tablefull("proc", "increase kern.maxproc or NPROC");
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return (EAGAIN);
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}
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nprocs++;
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/*
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* Increment the count of procs running with this uid. Don't allow
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@ -135,6 +135,7 @@ fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
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if (__predict_false(uid != 0 && count >
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p1->p_rlimit[RLIMIT_NPROC].rlim_cur)) {
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(void)chgproccnt(uid, -1);
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nprocs--;
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return (EAGAIN);
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}
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@ -147,6 +148,7 @@ fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
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uaddr = uvm_km_valloc(kernel_map, USPACE);
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if (__predict_false(uaddr == 0)) {
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(void)chgproccnt(uid, -1);
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nprocs--;
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return (ENOMEM);
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}
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@ -156,94 +158,7 @@ fork1(struct proc *p1, int flags, int exitsig, void *stack, size_t stacksize,
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*/
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/* Allocate new proc. */
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newproc = pool_get(&proc_pool, PR_WAITOK);
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/*
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* BEGIN PID ALLOCATION.
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*/
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s = proclist_lock_write();
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/*
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* Find an unused process ID. We remember a range of unused IDs
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* ready to use (from nextpid+1 through pidchecked-1).
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*/
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nextpid++;
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retry:
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/*
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* If the process ID prototype has wrapped around,
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* restart somewhat above 0, as the low-numbered procs
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* tend to include daemons that don't exit.
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*/
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if (nextpid >= PID_MAX) {
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nextpid = 100;
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pidchecked = 0;
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}
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if (nextpid >= pidchecked) {
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const struct proclist_desc *pd;
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pidchecked = PID_MAX;
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/*
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* Scan the process lists to check whether this pid
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* is in use. Remember the lowest pid that's greater
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* than nextpid, so we can avoid checking for a while.
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*/
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pd = proclists;
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again:
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for (p2 = LIST_FIRST(pd->pd_list); p2 != 0;
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p2 = LIST_NEXT(p2, p_list)) {
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while (p2->p_pid == nextpid ||
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p2->p_pgrp->pg_id == nextpid ||
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p2->p_session->s_sid == nextpid) {
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nextpid++;
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if (nextpid >= pidchecked)
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goto retry;
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}
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if (p2->p_pid > nextpid && pidchecked > p2->p_pid)
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pidchecked = p2->p_pid;
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if (p2->p_pgrp->pg_id > nextpid &&
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pidchecked > p2->p_pgrp->pg_id)
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pidchecked = p2->p_pgrp->pg_id;
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if (p2->p_session->s_sid > nextpid &&
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pidchecked > p2->p_session->s_sid)
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pidchecked = p2->p_session->s_sid;
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}
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/*
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* If there's another list, scan it. If we have checked
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* them all, we've found one!
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*/
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pd++;
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if (pd->pd_list != NULL)
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goto again;
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}
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nprocs++;
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p2 = newproc;
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/* Record the pid we've allocated. */
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p2->p_pid = nextpid;
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/* Record the signal to be delivered to the parent on exit. */
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p2->p_exitsig = exitsig;
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/*
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* Put the proc on allproc before unlocking PID allocation
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* so that waiters won't grab it as soon as we unlock.
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*/
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p2->p_stat = SIDL; /* protect against others */
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p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */
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LIST_INSERT_HEAD(&allproc, p2, p_list);
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LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
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/*
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* END PID ALLOCATION.
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*/
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proclist_unlock_write(s);
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p2 = pool_get(&proc_pool, PR_WAITOK);
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/*
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* Make a proc table entry for the new process.
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@ -274,7 +189,7 @@ again:
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/*
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* Duplicate sub-structures as needed.
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* Increase reference counts on shared objects.
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* The p_stats and p_sigacts substructs are set in vm_fork.
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* The p_stats and p_sigacts substructs are set in uvm_fork().
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*/
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p2->p_flag = P_INMEM | (p1->p_flag & P_SUGID);
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p2->p_emul = p1->p_emul;
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@ -368,6 +283,89 @@ again:
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(func != NULL) ? func : child_return,
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(arg != NULL) ? arg : p2);
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/*
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* BEGIN PID ALLOCATION.
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*/
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s = proclist_lock_write();
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/*
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* Find an unused process ID. We remember a range of unused IDs
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* ready to use (from nextpid+1 through pidchecked-1).
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*/
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nextpid++;
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retry:
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/*
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* If the process ID prototype has wrapped around,
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* restart somewhat above 0, as the low-numbered procs
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* tend to include daemons that don't exit.
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*/
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if (nextpid >= PID_MAX) {
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nextpid = 100;
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pidchecked = 0;
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}
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if (nextpid >= pidchecked) {
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const struct proclist_desc *pd;
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pidchecked = PID_MAX;
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/*
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* Scan the process lists to check whether this pid
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* is in use. Remember the lowest pid that's greater
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* than nextpid, so we can avoid checking for a while.
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*/
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pd = proclists;
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again:
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LIST_FOREACH(tp, pd->pd_list, p_list) {
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while (tp->p_pid == nextpid ||
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tp->p_pgrp->pg_id == nextpid ||
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tp->p_session->s_sid == nextpid) {
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nextpid++;
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if (nextpid >= pidchecked)
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goto retry;
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}
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if (tp->p_pid > nextpid && pidchecked > tp->p_pid)
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pidchecked = tp->p_pid;
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if (tp->p_pgrp->pg_id > nextpid &&
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pidchecked > tp->p_pgrp->pg_id)
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pidchecked = tp->p_pgrp->pg_id;
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if (tp->p_session->s_sid > nextpid &&
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pidchecked > tp->p_session->s_sid)
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pidchecked = tp->p_session->s_sid;
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}
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/*
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* If there's another list, scan it. If we have checked
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* them all, we've found one!
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*/
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pd++;
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if (pd->pd_list != NULL)
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goto again;
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}
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/* Record the pid we've allocated. */
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p2->p_pid = nextpid;
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/* Record the signal to be delivered to the parent on exit. */
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p2->p_exitsig = exitsig;
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/*
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* Put the proc on allproc before unlocking PID allocation
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* so that waiters won't grab it as soon as we unlock.
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*/
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p2->p_stat = SIDL; /* protect against others */
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p2->p_forw = p2->p_back = NULL; /* shouldn't be necessary */
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LIST_INSERT_HEAD(&allproc, p2, p_list);
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LIST_INSERT_HEAD(PIDHASH(p2->p_pid), p2, p_hash);
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/*
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* END PID ALLOCATION.
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*/
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proclist_unlock_write(s);
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/*
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* Make child runnable, set start time, and add to run queue.
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*/
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