Hi,
On Tuesday, 5 December 2006 15:12, Pavel Machek wrote:
> Hi!
>
> > > > Actually, what do you think about this patch? It removes special
> > > > handling of TASK_TRACED, and should do the trick, too...
> > >
> > > I was surprised, but the patch seems to work okay. Can you replace
> > > your 1/2 with this one, and see what breaks?
> >
> > I don't think anything will _visibly_ break, because (1) even if the traced
> > task has TIF_SIGPENDING set unnecessarily, it will just notice there is no
> > real signal to handle and continue and
>
> We are generating spurious wakeups, but as you noticed, that should be
> okay.
So we can move the check to freezeable(). Fine.
> >(2) the race between the delivery of
> > the continuation signal and the freezer is damn hard to trigger (still I
> > think
> > I can wirte some artificial code that would trigger this, although it would
> > involve a kernel thread sending SIGCONT to a user space process - provided
> > it's permissible ;-)).
>
> It is not really permissible, but I do not see how it would hurt...
>
> With that patch, we put TASK_STOPPED tasks into refrigerator, along
> with everyone else. SIGCONT is *not* going to help them out of
> refrigerator.
>
> We also ignore TASK_STOPPED now, so we'll not proceed until all
> stopped tasks are in refrigerator.
>
> Now... I'm not 100% sure I got the ptrace() cases right (and did not
> test that)... but TASK_STOPPED cases look pretty trivial to me now.
Please note that currently (and with your patch) freezeable() returns 0 for
TASK_STOPPED, so we don't set PF_FREEZE for them and my patch changes
_exactly_ that and adds some minor (optional) modifications to the error
paths.
Greetings,
Rafael
--
If you don't have the time to read,
you don't have the time or the tools to write.
- Stephen King
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