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Message-ID: <20080305172420.GA6751@tv-sign.ru>
Date: Wed, 5 Mar 2008 20:24:20 +0300
From: Oleg Nesterov <oleg@...sign.ru>
To: Roland McGrath <roland@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] introduce ptrace_reparented() helper
On 03/04, Roland McGrath wrote:
>
> > Somehow the patch I sent misses the change in ptrace.c, it can use the
> > new helper too.
>
> Actually, my pedantic streak prefers that to be in a separate patch.
> ...
> I don't object to the change, but it should be
> separate so bisect distinguishes it should it ever turn out to
> matter in some way we are now overlooking.
OK, agreed, will do.
> I'd even be a
> little inclined towards:
>
> if (child->real_parent == child->parent) {
> BUG_ON(!list_empty(&child->ptrace_list));
> return 0;
> } else {
> BUG_ON(list_empty(&child->ptrace_list));
> return 1;
> }
>
> except of course you couldn't use that in the reparent_thread case.
^^^^^^^^^^^^^^^
I can't believe. You are reading my mind!
I am planning to do some changes in forget_original_parent (fix 2 very
old minor bugs and _perhaps_ add some improvement). I hit the minor but
nasty problem: this open coded __ptrace_unlink() in reparent_thread().
_This_ is the actual reason for this patch.
So. Would you object if I do
--- kernel/ptrace.c 2008-03-03 17:01:06.000000000 +0300
+++ kernel/ptrace.c 2008-03-05 20:22:44.801142777 +0300
@@ -67,11 +67,12 @@ void ptrace_untrace(struct task_struct *
* remove it from the ptrace list.
*
* Must be called with the tasklist lock write-held.
+ *
+ * Either the caller is ptracer, or the caller is ->real_parent
+ * and the child is not traced.
*/
void __ptrace_unlink(struct task_struct *child)
{
- BUG_ON(!child->ptrace);
-
child->ptrace = 0;
if (ptrace_reparented(child)) {
list_del_init(&child->ptrace_list);
?
Oleg.
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