Re: [PATCH -mm 1/2]: PM: Fix handling of stopped tasks

[Pavel Machek <pavel@ucw.cz>]

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.

>(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.

							Pavel
-- 
Thanks for all the (sleeping) penguins.

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