Ben,
On Mon, 19 Aug 2019, luoben wrote:
> 在 2019/8/15 下午10:58, Thomas Gleixner 写道:
> > > This narrows the gap for setting up new irq (and irte, if has)
> > What does that mean: "narrows the gap"
> >
> > What's the gap and why is it only made smaller and not closed?
>
> Sorry for confusing. The so called 'gap' is a time window between free_irq()
> and request_irq().
And exactly this information wants to be in the changelog.
> > function please. Also it does not matter whether the time is short or
> > not. The point is:
> >
> > Ensure that an interrupt in flight on another CPU which uses
> > the
> > old 'dev_id' has completed because the caller can free the
> > memory
> > to which it points after this function returns.
> >
> > But this has another twist:
> >
> > CPU0 CPU1
> >
> > interrupt
> > primary_handler(old_dev_id)
> > do_stuff_on(old_dev_id)
> > return WAKE_THREAD; update_dev_id()
> > wakeup_thread();
> > action->dev_id = new_dev_id;
> > irq_thread()
> > secondary_handler(new_dev_id)
> >
> > That's broken and synchronize_irq() does not protect against it.
>
> Thanks to point it out, I will change to the following in next version, is
> that ok?
>
> ...
>
> /*
^^^
Please use a mail client which does not insert random wierd characters.
> * Ensure that an interrupt in flight on another CPU which uses the
> * old 'dev_id' has completed because the caller can free the memory
> * to which it points after this function returns. And also void to
s/void/avoid/
> * update 'dev_id' in the middle of a threaded interrupt process, it
> * can lead to a twist that primary handler uses old 'dev_id' but new
> * 'dev_id' is used by secondary handler.
> */
> disable_irq(irq);
Yes, that works.
Thanks,
tglx
