linux-kernel - Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE

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Message-ID: <20110214162036.GB11605@redhat.com>
Date:	Mon, 14 Feb 2011 17:20:36 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>,
	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 1/1] ptrace: make sure do_wait() won't hang after
	PTRACE_ATTACH

On 02/14, Tejun Heo wrote:
>
> Hello,
>
> On Mon, Feb 14, 2011 at 04:06:56PM +0100, Oleg Nesterov wrote:
> > This was (very briefly) discussed recently. Probably we can implement
> > PTRACE_DETACH_RUNNING (the name is random) which doesn't require the
> > stopped tracee but ignores the "data" argument.
>
> I think the root problem is not how ptrace detaches but how ptrace
> attaches and stops tracee.

Agreed, but please note that currently it is _very_ nontrivial to detach
correctly.

> If we have a clean way to seize the
> tracee, how we detach doesn't really matter.  For example, a new
> ptrace call which stops the tracee and puts it in a ptrace command
> ready state without messing with the signal and group stop stuff.

Indeed. Also briefly discussed: PTRACE_INTERRUPT.

Oleg.

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