How to establish a priority to an interrupt handler

How to establish a priority to an interrupt handler

[Monica Puig-Pey]

Hi,

I'm using Ubuntu 10.04 with the 2.6.31-11-rt patch installed. I'm
developing a PCI device driver using hardware interrupts.
As I read at the RT wiki
(https://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch )
interrupts are moved to kernel threads called Threaded Interrupts in the
RT patch.

I would like to give a priority chosen by me to my IRQ handler, but I
don't know how to do it, or if it is possible (it seems it is).

I've found (http://lwn.net/Articles/302043/ ) that what I had to use in
order to get Threaded Interrupt is:

int request_threaded_irq(unsigned int irq, irq_handler_t handler,
                      irq_handler_t quick_check_handler,
                      unsigned long flags, const char *name, void *dev)

But there is not priority there!

Using ps -eo pid,pri,rtprio,cmd I've seen my handler runs with priority 50.

I also used :

int request_irq (unsigned int irq, void (*handler) (int, void *, struct
pt_regs *), unsigned long irqflags, const char *devname, void *dev_id);

and using ps command here my handler still runs with priority 50.
Shouldn't it work as a non threaded interrupt then? Why 50 instead 99 or
the highest priority one?

Which function should I use to chose the priority for the IRQ thread?

Is there any other function to call from this context where my handler
could know its priority?

Please I wish to be personally CC'ed the answers/comments posted to the 
list in response to my posting because I'm not subscribed to the list.

Thank you very much

Mónica

Re: How to establish a priority to an interrupt handler

[Clemens Ladisch]

Monica Puig-Pey wrote:
> I'm developing a PCI device driver using hardware interrupts.
> I would like to give a priority chosen by me to my IRQ handler,

Please note that
1) priorities are relative to the other priorites currently in use,
   so assigning a fixed priority does not make sense unless you know
   all the other priorites; and
2) it is the job of the administrator, not of the driver writer, to
   determine which device gets the highest priority.


Regards,
Clemens

Re: How to establish a priority to an interrupt handler

[David Kastrup]

Monica Puig-Pey <puigpeym@unican.es> writes:

> Hi,
>
> I'm using Ubuntu 10.04 with the 2.6.31-11-rt patch installed. I'm
> developing a PCI device driver using hardware interrupts.
> As I read at the RT wiki
> (https://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch )
> interrupts are moved to kernel threads called Threaded Interrupts in
> the RT patch.
>
> I would like to give a priority chosen by me to my IRQ handler, but I
> don't know how to do it, or if it is possible (it seems it is).

This may not answer your question, but

apt-get install rtirq-init

might be all you need to do in order to get the interrupt priorities set
and sorted out for your purposes (well, for sound
recording/processing/playback it usually works reasonably well).

Even if not, taking a look at what the rtirq service script does might
give you good ideas.

-- 
David Kastrup

How to establish a priority to an interrupt handler

[Monica Puig-Pey]

Hi,

I'm using Ubuntu 10.04 with the 2.6.31-11-rt patch installed. I'm 
developing a PCI device driver using hardware interrupts.
As I read at the RT wiki 
(https://rt.wiki.kernel.org/index.php/CONFIG_PREEMPT_RT_Patch ) 
interrupts are moved to kernel threads called Threaded Interrupts in the 
RT patch.

I would like to give a priority chosen by me to my IRQ handler, but I 
don't know how to do it, or if it is possible (it seems it is).

I've found (http://lwn.net/Articles/302043/ ) that what I had to use in 
order to get Threaded Interrupt is:

int request_threaded_irq(unsigned int irq, irq_handler_t handler,
                      irq_handler_t quick_check_handler,
                      unsigned long flags, const char *name, void *dev)

But there is not priority there!

Using ps -eo pid,pri,rtprio,cmd I've seen my handler runs with priority 50.

I also used :

int request_irq (unsigned int irq, void (*handler) (int, void *, struct 
pt_regs *), unsigned long irqflags, const char *devname, void *dev_id);

and using ps command here my handler still runs with priority 50. 
Shouldn't it work as a non threaded interrupt then? Why 50 instead 99 or 
the highest priority one?

Which function should I use to chose the priority for the IRQ thread?

Is there any other function to call from this context where my handler 
could know its priority?

Thank you

Mónica
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