Re: [pok-devel] [Discussion] IRQ handling: chaining && pending IRQs

[Julien Delange <julien@xxxxxxxxx>]

Obviously, this would require to read the x86 manual again ... Laurent, Julian or Jeremy may have a direct answer because they work more on the lower-level aspects ... Anyway, if you think some changes are needed, feel free to do it as long as you do not break the existing code ! :)

On Thu, Aug 8, 2013 at 6:10 AM, Philipp Eppelt <philipp.eppelt@xxxxxxxxxxxxxxxxxxxxx> wrote:

Hi,

I have a question about the interrupt handling code.

In the x86 interrupt.h file [0], there is a "subl $4, %esp" in line 61
and 116 so in the interrupt handler code and in the syscall handler code.
But this instruction is missing in the errorcode handler code.

Shouldn't "subl $4, %esp" after "cli" in line 88? Because there is an
addl $4, %esp" right before "sti" in line 102.

Cheers,
Philipp


[0]
https://github.com/phipse/pok/blob/master/kernel/include/arch/x86/interrupt.h

On 08/01/2013 11:41 AM, Philipp Eppelt wrote:
> Hi,
>
> currently the interrupt handling does not support two features,
> necessary for my GSoC project: interrupt chaining and delivering pending
> interrupts.
>
> If one partition registers a handler for IRQ 0, then no other partition
> is able to register a handler for the same interrupt line.
> As I want to run several RTEMS instances in different partitions on POK
> one day, I need to be able to pass the clock IRQ on to every partition
> needing it.
>
> I come from the L4 microkernel world and are used to stuff like that,
> but it might introduce an overhead you are not willing to pay for in the
> embedded world. I appreciate a lively discussion about this change.
>
> I have put together a blog post, with a little bit of source code.
> http://phipse.github.io/rtems/blog/2013/07/09/how-late-is-it/
>
> Here is a summary of the post.
>
> I propose a meta handler, registering the IRQ with POK. One meta handler
> per IRQ vector. The meta handler is intercepting the current
> registration process and stores the received handler in a array indexed
> by the current partition number. If several partition want to acquire
> the same IRQ vector, their handlers are stored in the array and get
> invoked when the IRQ fires and they are currently running.
> If they are not running the IRQ is stored in the pending array, also
> indexed by the partition number. When the scheduler changes partition it
> needs to check for pending interrupts for the selected partition on
> every meta handler and deliver them.
>
> Open questions: Where to store the meta-handler table.
>
>
> Cheers,
> Philipp
>
>