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

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Message-ID: <20110218211140.GA2066@host1.dyn.jankratochvil.net>
Date:	Fri, 18 Feb 2011 22:11:40 +0100
From:	Jan Kratochvil <jan.kratochvil@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Denys Vlasenko <vda.linux@...glemail.com>,
	Tejun Heo <tj@...nel.org>, Roland McGrath <roland@...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 Thu, 17 Feb 2011 20:19:52 +0100, Oleg Nesterov wrote:
> > > That is after PTRACE_DETACH(0) the process should remain `T (stopped)'
> > > iff the process was `T (stopped)' before PTRACE_ATTACH.
> > >  - PTRACE_DETACH(0)       should preserve `T (stopped)'.
> >
> > I assume you are thinking about PTRACE_ATTACH + wait():SIGSTOP
> > + PTRACE_DETACH(0) sequence.
> 
> plus it should be stopped before attach, I assume. Otherwise this
> not true with the current code.

I did not talk about the current code.  I was making a proposal of new
behavior (which should not break existing software).

If PTRACE_ATTACH was done on process with `T (stopped)' then after
PTRACE_DETACH(0) again the process should be `T (stopped)'.


Regards,
Jan
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