[src/trunk]: src/sys/kern Make sure the child of a posix_spawn operation is n...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/87ace45db4fe
branches:  trunk
changeset: 777929:87ace45db4fe
user:      martin <martin%NetBSD.org@localhost>
date:      Sat Mar 10 08:46:45 2012 +0000

description:
Make sure the child of a posix_spawn operation is not preempted during
the times when it does not have any vm_space.
Should fix PR kern/46153.

diffstat:

 sys/kern/kern_exec.c |  15 ++++++++++-----
 1 files changed, 10 insertions(+), 5 deletions(-)

diffs (61 lines):

diff -r f565349c0f03 -r 87ace45db4fe sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Sat Mar 10 07:54:17 2012 +0000
+++ b/sys/kern/kern_exec.c      Sat Mar 10 08:46:45 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.344 2012/02/21 04:13:22 christos Exp $ */
+/*     $NetBSD: kern_exec.c,v 1.345 2012/03/10 08:46:45 martin Exp $   */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.344 2012/02/21 04:13:22 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.345 2012/03/10 08:46:45 martin Exp $");
 
 #include "opt_exec.h"
 #include "opt_ktrace.h"
@@ -1739,11 +1739,13 @@
        register_t retval;
        bool have_reflock;
 
+       /* we have been created non-preemptable */
+       KASSERT(l->l_nopreempt == 1);
+
        /*
         * The following actions may block, so we need a temporary
         * vmspace - borrow the kernel one
         */
-       KPREEMPT_DISABLE(l);
        l->l_proc->p_vmspace = proc0.p_vmspace;
        pmap_activate(l);
        KPREEMPT_ENABLE(l);
@@ -1869,8 +1871,6 @@
        KPREEMPT_DISABLE(l);
        pmap_deactivate(l);
        l->l_proc->p_vmspace = NULL;
-       KPREEMPT_ENABLE(l);
-
 
        /* now do the real exec */
        rw_enter(&exec_lock, RW_READER);
@@ -1881,6 +1881,9 @@
        else if (error)
                goto report_error;
 
+       /* we now have our own vmspace */
+       KPREEMPT_ENABLE(l);
+
        /* done, signal parent */
        mutex_enter(&spawn_data->sed_mtx_child);
        cv_signal(&spawn_data->sed_cv_child_ready);
@@ -2230,6 +2233,8 @@
                kauth_cred_free(ocred);
        }
 
+       l2->l_nopreempt = 1; /* start it non-preemptable */
+
        /*
         * It's now safe for the scheduler and other processes to see the
         * child process.