Hi,
On 11/12/2012 05:57 PM, Punit Agrawal wrote:
> I am attaching a patch by Thomas Gleixner which adds a kernel
> command line parameter to set the defauilt IRQ affinity mask. Could
> you please integrate this in your tree for the next Linaro release?
>
> I've been using this patch for sometime now and it doesn't introduce
> any regressions. There is a possibility that this patch will make it
> upstream via the RT patches in the near future but in the meanwhile,
> we'd like to carry this patch as well.
>
> Cheers,
> Punit
>
> From 52a7d44f58a262e166575abc57aa0bd3bfc8cfbb Mon Sep 17 00:00:00 2001
> From: Thomas Gleixner <[email protected]>
> Date: Fri, 25 May 2012 16:59:47 +0200
> Subject: [PATCH] genirq: Add default affinity mask command line option
>
> If we isolate CPUs, then we don't want random device interrupts on
> them. Even w/o the user space irq balancer enabled we can end up with
> irqs on non boot cpus.
>
> Allow to restrict the default irq affinity mask.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> ---
> Documentation/kernel-parameters.txt | 9 +++++++++
> kernel/irq/irqdesc.c | 21 +++++++++++++++++++--
> 2 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 7d82468..00fedab 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1164,6 +1164,15 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted.
> See comment before ip2_setup() in
> drivers/char/ip2/ip2base.c.
>
> + irqaffinity= [SMP] Set the default irq affinity mask
> + Format:
> + <cpu number>,...,<cpu number>
> + or
> + <cpu number>-<cpu number>
> + (must be a positive range in ascending order)
> + or a mixture
> + <cpu number>,...,<cpu number>-<cpu number>
> +
> irqfixup [HW]
> When an interrupt is not handled search all handlers
> for it. Intended to get systems with badly broken
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 192a302..473b2b6 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -23,10 +23,27 @@
> static struct lock_class_key irq_desc_lock_class;
>
> #if defined(CONFIG_SMP)
> +static int __init irq_affinity_setup(char *str)
> +{
> + zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
> + cpulist_parse(str, irq_default_affinity);
Since cpulist_parse() sets all the bits of its cpumask argument, it's
not necessary to initialize them to zero during allocation, so I would
use alloc_cpumask_var() instead of zalloc_cpumask_var().
> + /*
> + * Set at least the boot cpu. We don't want to end up with
> + * bugreports caused by random comandline masks
> + */
> + cpumask_set_cpu(smp_processor_id(), irq_default_affinity);
> + return 1;
> +}
> +__setup("irqaffinity=", irq_affinity_setup);
> +
> static void __init init_irq_default_affinity(void)
> {
> - alloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
> - cpumask_setall(irq_default_affinity);
> +#ifdef CONFIG_CPUMASK_OFFSTACK
> + if (!irq_default_affinity)
> + zalloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
> +#endif
The #ifdefery is not necessary here, because if CONFIG_CPUMASK_OFFSTACK
is not defined irq_default_affinity cannot be NULL.
--
Francesco
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