Re: [PATCH 3/3] IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

David Brownell
2006-10-06T03:45:46Z

On Tuesday 03 October 2006 11:03 am, Alan Stern wrote:

> > > Notice another questionable use of hcd->state.
> >
> > Questionable in what way? When that code is called to clean up
> > after driver death, that loop must be ignored ... every pending I/O
> > can safely be scrubbed. That's the main point of that particular
> > HC_IS_RUNNING() test. In other cases, it's essential not to touch
> > DMA queue entries that the host controller is still using.
>
> Questionable because changes to hcd->state aren't synchronized with the
> driver. In this case it probably doesn't end up making any difference.

The driver changes hcd->state with its spinlock held ... or it did,
last time I audited that code.

> Removing "regs &&" might change other aspects too. For instance, does
> this routine ever get called from a timer routine, where regs would
> normally be NULL? In such situations removing "regs &&" would reverse
> the sense of the test.

As I said in my previous comments: should not be an issue. OHCI doesn't
have timers. That routine is normally called in_irq(), with the other
two call sites being cases where the controller is stopped.

- Dave