Re: [PATCH 10/11] ptrace: move JOBCTL_TRAPPING wait to wait(2) and ptrace_check_attach()

[Tejun Heo <tj@kernel.org>]

Hey,

On Thu, May 12, 2011 at 05:59:10PM +0200, Oleg Nesterov wrote:
> > I don't know.  Why is retrying hairy?  The whole waiting logic is
> > built for clean retries.  The suggested change just does it without
> > intervening sleeping and waking up.  I don't see anything particularly
> > hairy there.
> 
> As always, this is subjective. But I didn't mean -EAGAIN itself. In fact
> I was going to add this (simple) logic some time ago and kill the EXIT_DEAD
> state. Hmm, and I'd still like to do this...

Oh, I've been updating code and it's now using interruptible sleep +
-ERESTARTNOINTR return.  It's simpler and the freezer problem is gone
too.

> I meant the whole ptrace_wait_trapping() + lock dance + retry thing.
> But of course I do not pretend my feeling is right.

Yeah, it's more complex than I would have liked.  The problem is that
ptrace(2) isn't really equipped with facilities to handle async
events, so it's a bit painful to add async mechanism into the existing
mechanics, but most problems seem solvable.

> Also. _Perhaps_ we can rethink the SIGCONT trapping, and perhaps in
> this case do_wait() won't need any changes. May be.

But, if there's a better way, sure.

Thanks.

-- 
tejun