[PATCH] Add call to non-crashing cores through IPI

[Catalin Marinas]

On Tue, 2010-11-23 at 12:41 +0000, Mika Westerberg wrote:
> On Tue, Nov 23, 2010 at 12:37:04PM +0000, Catalin Marinas wrote:
> > On 23 November 2010 10:57, Per Fransson <per.fransson.ml at gmail.com> wrote:
> > >>> Am I right that deadlock can occur only if the same IPI was sent?
> > >>
> > >> Not necessarily. It depends on whether the CPU issuing the IPI needs
> > >> to wait for the completion of the cross-call. If you don't need to
> > >> wait, you can send the IPI with the interrupts disabled (the platform
> > >> smp_cross_call is already called with interrupts disabled).
> > >>
> > >
> > > Well, smp_call_function() only optionally waits. As long as we choose not to,
> > > using that function to ask the other cores to save their states and idle, should
> > > be ok, right? In that case we don't need another ipi_msg_type and we can do
> > > it with the interrupts of the ipi caller disabled.
> >
> > I think that should work but we still have a WARN_ON_ONCE in the
> > generic smp_call_function_*() if interrupts are disabled.
> 
> But when we are crashing we have oops_in_progress set:
> 
>         WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled()
>                      && !oops_in_progress);
> 
> so this warning is never printed, right?

Right. So just make sure the caller doesn't set the 'wait' argument.

-- 
Catalin