[src/netbsd-6]: src/sys/kern Pull up following revision(s) (requested by mart...

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

details:   https://anonhg.NetBSD.org/src/rev/c28ec1a15513
branches:  netbsd-6
changeset: 773915:c28ec1a15513
user:      riz <riz%NetBSD.org@localhost>
date:      Sat Mar 10 16:49:01 2012 +0000

description:
Pull up following revision(s) (requested by martin in ticket #107):
        sys/kern/kern_exec.c: revision 1.345
        sys/kern/kern_exec.c: revision 1.346
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.
Remove a KPREEMPT_ENABLE() in an error path I overlooked in the previous
change - pointed out by Manuel Bouyer.
While there, add a KASSERT() to make sure we have preemption enabled in
the success case.

diffstat:

 sys/kern/kern_exec.c |  18 ++++++++++++------
 1 files changed, 12 insertions(+), 6 deletions(-)

diffs (71 lines):

diff -r 908494019fc6 -r c28ec1a15513 sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Sat Mar 10 16:46:45 2012 +0000
+++ b/sys/kern/kern_exec.c      Sat Mar 10 16:49:01 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.339.2.2 2012/02/22 18:43:35 riz Exp $  */
+/*     $NetBSD: kern_exec.c,v 1.339.2.3 2012/03/10 16:49:01 riz Exp $  */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -59,7 +59,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.339.2.2 2012/02/22 18:43:35 riz Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_exec.c,v 1.339.2.3 2012/03/10 16:49:01 riz Exp $");
 
 #include "opt_exec.h"
 #include "opt_ktrace.h"
@@ -1778,11 +1778,13 @@
        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);
@@ -1908,8 +1910,6 @@
        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);
@@ -1920,6 +1920,10 @@
        else if (error)
                goto report_error;
 
+       /* we now have our own vmspace */
+       KPREEMPT_ENABLE(l);
+       KASSERT(l->l_nopreempt == 0);
+
        /* done, signal parent */
        mutex_enter(&spawn_data->sed_mtx_child);
        cv_signal(&spawn_data->sed_cv_child_ready);
@@ -1940,7 +1944,7 @@
                KPREEMPT_DISABLE(l);
                pmap_deactivate(l);
                l->l_proc->p_vmspace = NULL;
-               KPREEMPT_ENABLE(l);
+               /* do not enable preemption without vmspace */
        }
 
        /*
@@ -2269,6 +2273,8 @@
                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.