Re: [Linux-ia64] ia64_mca_rendez_int_handler use of hard_smp_processor_id

Keith Owens
2003-03-25T21:15:30Z

On Tue, 25 Mar 2003 08:45:56 -0800,
"Luck, Tony" <tony.luck@intel.com> wrote:
>>>>>> On Sat, 22 Mar 2003 15:12:55 +1100, Keith Owens <kaos@sgi.com> >said:
>
> Keith> arch/ia64/kernel/mca.c:ia64_mca_rendez_int_handler has
> Keith> #ifdef CONFIG_SMP
> Keith> cpu = cpu_logical_id(hard_smp_processor_id());
> Keith> #endif
> Keith> ia64_mc_info.imi_rendez_checkin[cpu] = >IA64_MCA_RENDEZ_CHECKIN_DONE;
>
> Keith> All the other code that runs imi_rendez_checkin does so using >logical
> Keith> cpu numbers. Why does ia64_mca_rendez_int_handler use that >convoluted
> Keith> expression instead of the simpler
> Keith> cpu = smp_processor_id();
>
> David> I don't know either. Perhaps the original author remembers >(Jenna or
> David> Tony, perhaps?).
>
>This code predates me. I checked with Jenna and she says that it's >before
>her time too.
>
><speculation>
>That convoluted expression avoids use of the per-cpu mapping, but I >can't see
>why we'd be scared to use that here, and not be paranoid elsewhere. How >was
>smp_processor_id() implemented far back in days of 2.4.0 and before?
></speculation>

At one time there was confusion between which arrays used the logical
cpu number in smp_processor_id() and which arrays used the hardware cpu
number. This is probably a holdover from that period.

Index: 20.5/arch/ia64/kernel/mca.c
--- 20.5/arch/ia64/kernel/mca.c Wed, 11 Dec 2002 20:58:53 +1100 kaos (linux-2.4/s/c/5_mca.c 1.1.3.2.3.1.1.1.1.3 644)
+++ 20.5(w)/arch/ia64/kernel/mca.c Wed, 26 Mar 2003 08:14:29 +1100 kaos (linux-2.4/s/c/5_mca.c 1.1.3.2.3.1.1.1.1.3 644)
@@ -640,13 +640,10 @@ ia64_mca_wakeup_all(void)
void
ia64_mca_rendez_int_handler(int rendez_irq, void *arg, struct pt_regs *ptregs)
{
- int flags, cpu = 0;
+ int flags, cpu = smp_processor_id();
/* Mask all interrupts */
save_and_cli(flags);

-#ifdef CONFIG_SMP
- cpu = cpu_logical_id(hard_smp_processor_id());
-#endif
ia64_mc_info.imi_rendez_checkin[cpu] = IA64_MCA_RENDEZ_CHECKIN_DONE;
/* Register with the SAL monarch that the slave has
* reached SAL