Re: linux-next: build failure after merge of the tip tree

Peter Zijlstra
2014-01-16T12:14:15Z

On Tue, Jan 14, 2014 at 04:43:43PM -0500, Mikulas Patocka wrote:
> > @@ -200,7 +201,9 @@ static void speedstep_set_state(unsigned int state)
> > if (retry) {
> > pr_debug("retry %u, previous result %u, waiting...\n",
> > retry, result);
> > + local_irq_restore(flags);
>
> ^^^ this is wrong, because the function speedstep_set_state may already be
> called with interrupts disabled from speedstep_get_freqs. So, you need to
> enable interrupts unconditionally, even if they were disabled at the
> beginning of the function speedstep_set_state.
>
> I know it's dirty to enable interrupts in a function that was called with
> disabled interrupts, but here it must be so (you could rewrite
> speedstep_get_freqs to not disable interrupts if you want to avoid this
> dirtiness).

Egads; I think you had better, this is vile beyond reason.

> > mdelay(retry * 50);
> > + local_irq_save(flags);
> > }
> > retry++;
> > __asm__ __volatile__(
> > @@ -217,6 +220,7 @@ static void speedstep_set_state(unsigned int state)
> >
> > /* enable IRQs */
> > local_irq_restore(flags);
> > + preempt_enable();
> >
> > if (new_state == state)
> > pr_debug("change to %u MHz succeeded after %u tries "
>
> You need also preempt_disable/enable in speedstep_get_freqs.

Argh I see, this is really horrid.

Anyway, its Rafael's call, its his subsystem he gets to fix it when it
explodes.

/me shudders