linux-kernel - Re: [PATCH 04/10] ptrace: implement PTRACE

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Message-ID: <20110519120723.GE627@htj.dyndns.org>
Date:	Thu, 19 May 2011 14:07:23 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	jan.kratochvil@...hat.com, vda.linux@...glemail.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com
Subject: Re: [PATCH 04/10] ptrace: implement PTRACE_INTERRUPT

Hello,

On Wed, May 18, 2011 at 08:38:15PM +0200, Oleg Nesterov wrote:
> On 05/16, Tejun Heo wrote:
> >
> > +	case PTRACE_INTERRUPT:
> > +		/*
> > +		 * Stop tracee without any side-effect on signal or job
> > +		 * control.  At least one trap is guaranteed to happen
> > +		 * after this request.  If @child is already trapped, the
> > +		 * current trap is not disturbed and another trap will
> > +		 * happen after the current trap is ended with PTRACE_CONT.
> > +		 *
> > +		 * The actual trap might not be PTRACE_EVENT_STOP trap but
> > +		 * the pending condition is cleared regardless.
> > +		 */
> > +		if (likely(child->ptrace & PT_SEIZED) &&
> > +		    lock_task_sighand(child, &flags)) {
> > +			child->jobctl |= JOBCTL_TRAP_STOP;
> 
> The same race with do_signal_stop() afaics.

I didn't understand that one, so you'll need to elaborate.

> Otherwise looks fine to me. Compared to V1, personally I like the new
> behaviour more. PTRACE_INTERRUPT and PTRACE_SEIZE do the same.

Great. :)

Thanks.

-- 
tejun
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