Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap - Kernel

This is a discussion on Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap - Kernel ; On Fri, Oct 10, 2008 at 04:01:54PM -0400, Stefan Bader wrote: > Affected: 2.6.24-2.6.27 > > Someone from the community found out, that after repeatedly unloading and > loading a device driver that uses MSI IRQs, the system eventually assigned ...

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Thread: Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

  1. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    On Fri, Oct 10, 2008 at 04:01:54PM -0400, Stefan Bader wrote:
    > Affected: 2.6.24-2.6.27
    >
    > Someone from the community found out, that after repeatedly unloading and
    > loading a device driver that uses MSI IRQs, the system eventually assigned
    > the vector initially reserved for IRQ0 to the device driver.
    >
    > The reason for this is, that although IRQ0 is tied to the FIRST_DEVICE_VECTOR
    > when declaring the irq_vector table, the corresponding bit in the used_vectors
    > map is not set. So, if vectors are released and assigned often enough, the
    > vector will get assigned to another interrupt. This happens more often with
    > MSI interrupts as those are exclusively using a vector.


    Is there a problem with being assigned to IRQ0 in situations like this?

    thanks,

    greg k-h
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  2. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    Greg KH wrote:
    >
    > Is there a problem with being assigned to IRQ0 in situations like this?
    >


    On PCs, IRQ 0 is dedicated to use for the PIT.

    -hpa
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  3. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    On Fri, Oct 10, 2008 at 01:35:48PM -0700, H. Peter Anvin wrote:
    > Greg KH wrote:
    >> Is there a problem with being assigned to IRQ0 in situations like this?

    >
    > On PCs, IRQ 0 is dedicated to use for the PIT.


    Ah, I didn't realize it couldn't be shared.

    thanks,

    greg k-h
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  4. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    On Fri, 10 Oct 2008 13:41:33 -0700
    Greg KH wrote:

    > On Fri, Oct 10, 2008 at 01:35:48PM -0700, H. Peter Anvin wrote:
    > > Greg KH wrote:
    > >> Is there a problem with being assigned to IRQ0 in situations like this?

    > >
    > > On PCs, IRQ 0 is dedicated to use for the PIT.

    >
    > Ah, I didn't realize it couldn't be shared.


    And more importantly dev->irq == 0 or IRQ == 0 to anything but arch
    internal code means "no interrupt line".
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  5. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    On Fri, Oct 10, 2008 at 09:50:38PM +0100, Alan Cox wrote:
    > On Fri, 10 Oct 2008 13:41:33 -0700
    > Greg KH wrote:
    >
    > > On Fri, Oct 10, 2008 at 01:35:48PM -0700, H. Peter Anvin wrote:
    > > > Greg KH wrote:
    > > >> Is there a problem with being assigned to IRQ0 in situations like this?
    > > >
    > > > On PCs, IRQ 0 is dedicated to use for the PIT.

    > >
    > > Ah, I didn't realize it couldn't be shared.

    >
    > And more importantly dev->irq == 0 or IRQ == 0 to anything but arch
    > internal code means "no interrupt line".


    I thought we had changed that a while ago, as some arches had 0 as a
    valid irq line.

    Anyway, thanks all for the information, I appreciate it.

    greg k-h
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  6. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    > > And more importantly dev->irq == 0 or IRQ == 0 to anything but arch
    > > internal code means "no interrupt line".

    >
    > I thought we had changed that a while ago, as some arches had 0 as a
    > valid irq line.


    No .. Linus decreed (and I think sensibly myself that IRQ = 0 meant no
    IRQ assigned).. the argument being that in C you naturally write stuff
    like

    if (!dev->irq)

    I can dig up the reference URLS to the list mails if you want
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  7. Re: [stable] [PATCH] x86: Reserve FIRST_DEVICE_VECTOR in used_vectors bitmap

    On Fri, Oct 10, 2008 at 10:49:07PM +0100, Alan Cox wrote:
    > > > And more importantly dev->irq == 0 or IRQ == 0 to anything but arch
    > > > internal code means "no interrupt line".

    > >
    > > I thought we had changed that a while ago, as some arches had 0 as a
    > > valid irq line.

    >
    > No .. Linus decreed (and I think sensibly myself that IRQ = 0 meant no
    > IRQ assigned).. the argument being that in C you naturally write stuff
    > like
    >
    > if (!dev->irq)


    Ok, I was confused, thanks.

    > I can dig up the reference URLS to the list mails if you want


    Nah, I trust you

    thanks,

    greg k-h
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