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    SubjectRe: Regression: Bisected, IRQ and MSI allocations screwed without sparse irq
    Jesper,

    On Thu, 20 Nov 2008, Jesper Dangaard Brouer wrote:
    > I have bisected a regression to your commit
    > 3235e936c0cc3589309280b6f59e5096779adae3,
    > "x86: remove sparse irq from Kconfig".
    >
    > Its actually not necessary your fault, as your commit simply removes
    > the config option HAVE_SPARSE_IRQ. This revels the bug / regression
    > I'm exposted to.

    Yup, the bisect result is pretty useless.

    > The cause of this problem (tracked down together with Robert Olsson)
    > is that on 2.6.28 I have a lot less IRQs available. It seems max 34
    > IRQs. Due the reduced number of IRQs the NIU driver cannot get
    > enough IRQs to the interfaces, and starts to use "IO-APIC" based
    > IRQs.

    Can you please try the attached patch ?

    Thanks,

    tglx

    -----
    arch/x86/kernel/io_apic.c | 22 +---------------------
    1 file changed, 1 insertion(+), 21 deletions(-)

    Index: linux-2.6/arch/x86/kernel/io_apic.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/io_apic.c
    +++ linux-2.6/arch/x86/kernel/io_apic.c
    @@ -3594,27 +3594,7 @@ int __init io_apic_get_redir_entries (in

    int __init probe_nr_irqs(void)
    {
    - int idx;
    - int nr = 0;
    -#ifndef CONFIG_XEN
    - int nr_min = 32;
    -#else
    - int nr_min = NR_IRQS;
    -#endif
    -
    - for (idx = 0; idx < nr_ioapics; idx++)
    - nr += io_apic_get_redir_entries(idx) + 1;
    -
    - /* double it for hotplug and msi and nmi */
    - nr <<= 1;
    -
    - /* something wrong ? */
    - if (nr < nr_min)
    - nr = nr_min;
    - if (WARN_ON(nr > NR_IRQS))
    - nr = NR_IRQS;
    -
    - return nr;
    + return NR_IRQS;
    }

    /* --------------------------------------------------------------------------

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