On Sun, 12 Dec 2010, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
>
> This enabled interrupt handlers to retrieve the current line sharing state via
> the new interrupt status word so that they can adapt to it.
>
> The switch from shared to exclusive is generally uncritical and can thus be
> performed on demand. However, preparing a line for shared mode may require
> preparational steps of the currently registered handler. It can therefore
> request an ahead-of-time notification via IRQF_ADAPTIVE. The notification
> consists of an exceptional handler invocation with IRQS_MAKE_SHAREABLE set in
> the status word.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
> include/linux/interrupt.h | 10 ++++++++++
> include/linux/irqdesc.h | 2 ++
> kernel/irq/irqdesc.c | 2 ++
> kernel/irq/manage.c | 44 +++++++++++++++++++++++++++++++++++++++++---
> 4 files changed, 55 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index 16cdbbf..c6323a2 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -55,6 +55,7 @@
> * Used by threaded interrupts which need to keep the
> * irq line disabled until the threaded handler has been run.
> * IRQF_NO_SUSPEND - Do not disable this IRQ during suspend
> + * IRQF_ADAPTIVE - Request notification about upcoming interrupt line sharing
> *
> */
> #define IRQF_DISABLED 0x00000020
> @@ -67,6 +68,7 @@
> #define IRQF_IRQPOLL 0x00001000
> #define IRQF_ONESHOT 0x00002000
> #define IRQF_NO_SUSPEND 0x00004000
> +#define IRQF_ADAPTIVE 0x00008000
>
> #define IRQF_TIMER (__IRQF_TIMER | IRQF_NO_SUSPEND)
>
> @@ -126,6 +128,14 @@ struct irqaction {
>
> extern irqreturn_t no_action(int cpl, void *dev_id);
>
> +/*
> + * Driver-readable IRQ line status flags:
> + * IRQS_SHARED - line is shared between multiple handlers
> + * IRQS_MAKE_SHAREABLE - in the process of making an exclusive line shareable
> + */
> +#define IRQS_SHARED 0x00000001
> +#define IRQS_MAKE_SHAREABLE 0x00000002
> +
> extern unsigned long get_irq_status(unsigned long irq);
>
> #ifdef CONFIG_GENERIC_HARDIRQS
> diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
> index 979c68c..c490e83 100644
> --- a/include/linux/irqdesc.h
> +++ b/include/linux/irqdesc.h
> @@ -29,6 +29,7 @@ struct timer_rand_state;
> * @wait_for_threads: wait queue for sync_irq to wait for threaded handlers
> * @dir: /proc/irq/ procfs entry
> * @name: flow handler name for /proc/interrupts output
> + * @register_lock: protects registration & release, for unshared->shared
I think we can make that a global mutex. request/free_irq are not
hotpath operations which require a mutex per irq descriptor.
Thanks,
tglx
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