[src/trunk]: src/sys/kern Follow the correct locking protocol when creating a...

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

details:   https://anonhg.NetBSD.org/src/rev/e551d3fae024
branches:  trunk
changeset: 755442:e551d3fae024
user:      skrll <skrll%NetBSD.org@localhost>
date:      Sun Jun 06 07:46:17 2010 +0000

description:
Follow the correct locking protocol when creating an LWP and the process
is stopping.

Problem found by running the gdb testsuite (gdb didn't have pthreads
support)

Thanks to rmind for help with this.

diffstat:

 sys/kern/sys_lwp.c |  18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diffs (55 lines):

diff -r a550af22a374 -r e551d3fae024 sys/kern/sys_lwp.c
--- a/sys/kern/sys_lwp.c        Sun Jun 06 06:20:16 2010 +0000
+++ b/sys/kern/sys_lwp.c        Sun Jun 06 07:46:17 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_lwp.c,v 1.49 2010/04/23 19:18:09 rmind Exp $       */
+/*     $NetBSD: sys_lwp.c,v 1.50 2010/06/06 07:46:17 skrll Exp $       */
 
 /*-
  * Copyright (c) 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -35,7 +35,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_lwp.c,v 1.49 2010/04/23 19:18:09 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_lwp.c,v 1.50 2010/06/06 07:46:17 skrll Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -82,6 +82,7 @@
        } */
        struct proc *p = l->l_proc;
        struct lwp *l2;
+       struct schedstate_percpu *spc;
        vaddr_t uaddr;
        ucontext_t *newuc;
        int error, lid;
@@ -133,20 +134,23 @@
         */
        mutex_enter(p->p_lock);
        lwp_lock(l2);
+       spc = &l2->l_cpu->ci_schedstate;
        if ((SCARG(uap, flags) & LWP_SUSPENDED) == 0 &&
            (l->l_flag & (LW_WREBOOT | LW_WSUSPEND | LW_WEXIT)) == 0) {
-               if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0)
+               if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0) {
+                       KASSERT(l2->l_wchan == NULL);
                        l2->l_stat = LSSTOP;
-               else {
-                       KASSERT(lwp_locked(l2, l2->l_cpu->ci_schedstate.spc_mutex));
+                       lwp_unlock_to(l2, spc->spc_lwplock);
+               } else {
+                       KASSERT(lwp_locked(l2, spc->spc_mutex));
                        p->p_nrlwps++;
                        l2->l_stat = LSRUN;
                        sched_enqueue(l2, false);
+                       lwp_unlock(l2);
                }
-               lwp_unlock(l2);
        } else {
                l2->l_stat = LSSUSPENDED;
-               lwp_unlock_to(l2, l2->l_cpu->ci_schedstate.spc_lwplock);
+               lwp_unlock_to(l2, spc->spc_lwplock);
        }
        mutex_exit(p->p_lock);