Re: [ACPI] ACPI using smp_processor_id in preemptible code

[Con Kolivas <kernel@xxxxxxxxxxx>]

Li Shaohua wrote:
> On Mon, 2005-01-10 at 17:55, Pavel Machek wrote:
>
> > > > I enabled CPU hotplug and preemptible debugging... now I get...
> > > >
> > > > BUG: using smp_processor_id() in preemptible [00000001] code:
> > > > swapper/0
> > > > caller is acpi_processor_idle+0xb/0x235
> > > > [<c020ba28>] smp_processor_id+0xa8/0xc0
> > > > [<c02338ce>] acpi_processor_idle+0xb/0x235
> > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
> > > > [<c02338ce>] acpi_processor_idle+0xb/0x235
> > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
> > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
> > > > [<c02338c3>] acpi_processor_idle+0x0/0x235
> > > > [<c0101115>] cpu_idle+0x75/0x110
> > > > [<c04f5988>] start_kernel+0x158/0x180
> > > > [<c04f5390>] unknown_bootoption+0x0/0x1e0
> > >
> > > It doesn't trouble to me. It's in idle thread.
> >
> > You mean it does not happen to you? On my machine it fills logs very
> > quickly...
>
> What I mean is idle thread can't be migrated so this doesn't impact the
> correctness. I guess the preemptible debugging can't recognise such
> situation.

This patch should help. If it's safe to use smp_processor_id() in 
acpi_processor_idle use the alternative call.

Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>
Index: linux-2.6.10-mm2/drivers/acpi/processor_idle.c
===================================================================
--- linux-2.6.10-mm2.orig/drivers/acpi/processor_idle.c	2005-01-11 12:20:31.399070008 +1100
+++ linux-2.6.10-mm2/drivers/acpi/processor_idle.c	2005-01-11 12:22:19.931570560 +1100
@@ -162,7 +162,7 @@
 	int			sleep_ticks = 0;
 	u32			t1, t2 = 0;
 
-	pr = processors[smp_processor_id()];
+	pr = processors[_smp_processor_id()];
 	if (!pr)
 		return;