Re: [RFC,PATCH 14/14] utrace core

[Roland McGrath]

> On 12/14, Oleg Nesterov wrote:
> >
> > IOW, we must ensure that if ever clear TIF_NOTIFY_RESUME we must not
> > miss ->pending_attach, correct? and for this case we have mb() after
> > clear_thread_flag(). Perhaps instead we should add mb__after_clear_bit()
> > into arch/ hooks, but this needs a lot of arch-dependent changes.

Since it's utrace/tracehook code that relies on the barrier I think it
makes sense to have it in tracehook_notify_resume() or utrace_resume().
The arch requirement is having done clear_thread_flag() beforehand, so the
arch-independent code can reasonably assume whatever semantics that is
guaranteed to have.

> Cough. And I always read this "rmb" as "mb". Even when I changed
> the comment to explain that we need a barrier between clear bit
> and read flags, I didn't notice it is in fact rmb...
> 
> I guess we need the trivial fix, Roland?

You're the barrier man, send me what changes it should get.


Thanks,
Roland
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/