[src/trunk]: src/sys/kern Fix kernel panic triggered with LLDB

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

details:   https://anonhg.NetBSD.org/src/rev/b453a78461d6
branches:  trunk
changeset: 353398:b453a78461d6
user:      kamil <kamil%NetBSD.org@localhost>
date:      Wed May 03 15:53:31 2017 +0000

description:
Fix kernel panic triggered with LLDB

PT_SETSTEP and PT_CLEARSTEP in the current design must unlock proc_lock and
t->p_lock. These functions use lwp_delref() for a tracee with more than one
LWP. This function internally lock (t->)p_lock and this is lock against
self.

There are coming new ATF test with PT_*STEP with multiple LWPs to catch
these bugs in future changes.

Sponsored by <The NetBSD Foundation>

diffstat:

 sys/kern/sys_ptrace_common.c |  6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diffs (27 lines):

diff -r 86ccfe995411 -r b453a78461d6 sys/kern/sys_ptrace_common.c
--- a/sys/kern/sys_ptrace_common.c      Wed May 03 15:34:05 2017 +0000
+++ b/sys/kern/sys_ptrace_common.c      Wed May 03 15:53:31 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_ptrace_common.c,v 1.21 2017/04/08 00:25:50 kamil Exp $     */
+/*     $NetBSD: sys_ptrace_common.c,v 1.22 2017/05/03 15:53:31 kamil Exp $     */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -118,7 +118,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.21 2017/04/08 00:25:50 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_ptrace_common.c,v 1.22 2017/05/03 15:53:31 kamil Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ptrace.h"
@@ -536,8 +536,6 @@
        switch (req) {
 #ifdef PT_STEP
        case PT_STEP:
-       case PT_SETSTEP:
-       case PT_CLEARSTEP:
 #endif
        case PT_CONTINUE:
        case PT_DETACH: