Re: [PATCH 04/10] ptrace: implement PTRACE_INTERRUPT

[Oleg Nesterov <oleg@redhat.com>]

On 05/19, Tejun Heo wrote:
>
> 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,

Yeah, I was wrong, see the previous email.

Oleg.