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

Thomas Gleixner
2008-11-21T00:34:53Z

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;
}

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