On Thu, 03 May 2007 07:56:02 -0500
John Keller <[email protected]> wrote:
> On SN, only allow one bit to be set in the smp_affinty mask
> when redirecting an interrupt. Currently setting multiple
> bits is allowed, but only the first bit is used in
> determining the CPU to redirect to. This has caused confusion
> among some customers.
>
> ...
>
> +
> +int is_affinity_mask_valid(cpumask_t cpumask)
> +{
> + if (ia64_platform_is("sn2")) {
> + /* Only allow one CPU to be specified in the smp_affinity mask */
> + if (cpus_weight(cpumask) != 1)
> + return 0;
> + }
> + return 1;
> +}
A bool returning true or false would be appropriate, given this function's
clearly-boolean name.
> +#ifndef ARCH_HAS_IRQ_AFFINITY_VALIDATION
> +#define is_irq_affinity_mask_valid(cpumask) 1
> +#endif
The ARCH_HAS_FOO things have never been popular. There are a couple of
alternatives going around:
a) use __attribute__((weak)) and provide a one-line default
implementation in kernel/irq/proc.c. This has a small runtime cost.
b) In include/asm-ia64/irq.h, do
#define is_affinity_mask_valid is_affinity_mask_valid
and in kernel/irq/proc.c do
#ifndef is_affinity_mask_valid
#define is_affinity_mask_valid() 1
#endif
This has minimal runtime cost, but is a bit tricksy.
It has the advantage that it doesn't introduce some new identifier
which needs to be maintained.
> extern int irq_set_affinity(unsigned int irq, cpumask_t cpumask);
> extern int irq_can_set_affinity(unsigned int irq);
>
> Index: linux-2.6/include/asm-ia64/irq.h
> ===================================================================
> --- linux-2.6.orig/include/asm-ia64/irq.h 2007-05-01 15:47:01.660643076 -0500
> +++ linux-2.6/include/asm-ia64/irq.h 2007-05-01 15:48:42.729254805 -0500
> @@ -11,6 +11,8 @@
> * 02/29/00 D.Mosberger moved most things into hw_irq.h
> */
>
> +#include <linux/cpumask.h>
> +
This is the sort of inclusion which tends to make things blow up. I trust
this was carefully compile-tested.
With a) above, the is_affinity_mask_valid() declaration would be in a
different header. With b), no additional include will be needed.
> #define NR_IRQS 256
> #define NR_IRQ_VECTORS NR_IRQS
>
> @@ -30,4 +32,7 @@ extern void disable_irq_nosync (unsigned
> extern void enable_irq (unsigned int);
> extern void set_irq_affinity_info (unsigned int irq, int dest, int redir);
>
> +#define ARCH_HAS_IRQ_AFFINITY_VALIDATION
> +extern int is_affinity_mask_valid(cpumask_t cpumask);
> +
-
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