Re: get_irq_regs() from soft IRQ

[Jean Pihet <jpihet@mvista.com>]

On Monday 29 June 2009 18:07:44 Russell King - ARM Linux wrote:
> On Mon, Jun 29, 2009 at 05:35:37PM +0200, Jean Pihet wrote:
> > On Monday 29 June 2009 17:19:31 Russell King - ARM Linux wrote:
> > > It's one of these things that nests itself - when you have several IRQs
> > > being processed on one CPU, there are several register contexts saved,
> > > and get_irq_regs() returns the most recent one.
> > >
> > > > The use case is that the performance unit (PMNC) of the Cortex A8 has
> > > > some serious bug, in short the performance counters overflow IRQ is
> > > > to be avoided.
> > >
> > > I don't follow.  None of the PMNC support code in the mainline kernel
> > > uses get_irq_regs() outside of IRQ context.
> >
> > That is correct. The Cortex A8 needs some special treatment.
> > The errata says that if the counters are overflowing at the same time as
> > a coprocessor access is performed, the perf unit gets reset and/or locks
> > up. In short the counters overflow is to be avoided and so the PMNC IRQ.
>
> Are you talking about 628216?
Yes that is the one. Sorry not to mention it sooner.

Jean