linux-kernel - Re: [PATCH] ptrace: use safer wake up on ptrace

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Message-ID: <20110201191743.GA8913@redhat.com>
Date:	Tue, 1 Feb 2011 20:17:43 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Roland McGrath <roland@...hat.com>, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] ptrace: use safer wake up on ptrace_detach()

On 02/01, Tejun Heo wrote:
>
> Hello,
>
> On Tue, Feb 01, 2011 at 02:40:37PM +0100, Oleg Nesterov wrote:
> > On 02/01, Tejun Heo wrote:
> > >
> > > --- work.orig/kernel/ptrace.c
> > > +++ work/kernel/ptrace.c
> > > @@ -313,7 +313,7 @@ int ptrace_detach(struct task_struct *ch
> > >  		child->exit_code = data;
> > >  		dead = __ptrace_detach(current, child);
> > >  		if (!child->exit_state)
> > > -			wake_up_process(child);
> > > +			wake_up_state(child, TASK_TRACED | TASK_STOPPED);
> >
> > Well, it can't be TASK_TRACED at this point. And of course this still
> > contradicts to __set_task_state(child, TASK_STOPPED) in ptrace_untrace().
> > IOW, to me the previous patch makes more sense.
>
> Yeah, it can't be in TRACED but the whole point of the patch is
> avoiding rude wakeups, so as long as it doesn't end up waking random
> [un]interruptible sleeps...  It will be removed later anyway.

Yes, yes, I understand.

> > But OK, I understand Roland's concerns. And, at least this change
> > fixes the bug mentioned in 95a3540d.
> >
> > Acked-by: Oleg Nesterov <oleg@...hat.com>
>
> Oleg, Roland, you guys are the maintainers, so how do you guys want to
> route the patches which have been acked?

Well. I know only one way, send it to akpm ;)

> As it's likely that there
> will be quite some number of ptrace patches, it will be better to have
> a git tree.

Probably yes... but everything in this area goes through -mm so far.

Oleg.

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