smp_affinity weirdness in LK 2.6.14

smp_affinity weirdness in LK 2.6.14

[Dimitri Puzin]

Hello,

I found that I cannot change IRQ affinity in the 2.6.14 kernel. It works
however on the 2.6.13.4 and earlier.
2.6.13.4:
# cat /proc/irq/189/smp_affinity
1
# echo 2 > /proc/irq/189/smp_affinity
# cat /proc/irq/189/smp_affinity
2
#

2.6.14:
# cat /proc/irq/189/smp_affinity
1
# echo 2 > /proc/irq/189/smp_affinity
# cat /proc/irq/189/smp_affinity
1
#
/proc/interrupts is also showing that all all IRQs are bound to CPU0. I
must add, that this system is a P4 with HyperThreading support. I've
tried both with CONFIG_IRQBALANCE=y and n but the result is always the
same. With the new kernel I cannot balance the IRQs neither by hand, nor
userspace/kernel tools. Is that normal?

Regards
-Dimitri

Re: smp_affinity weirdness in LK 2.6.14

[Dimitri Puzin]

Dimitri Puzin schrieb:

>Hello,
>
>I found that I cannot change IRQ affinity in the 2.6.14 kernel. It works
>however on the 2.6.13.4 and earlier.
>
This got fixed with 2.6.15-rc4

commit fe655d3a06488c8a188461bca493e9f23fc8c448
Author: Shaohua Li <shaohua.li@intel.com>
Date:   Tue Nov 29 19:34:42 2005 -0800

    [PATCH] setting irq affinity is broken in ia32 with MSI enabled
    
    Setting irq affinity stops working when MSI is enabled.  With MSI, move_irq
    is empty, so we can't change irq affinity.  It appears a typo in Ashok's
    original commit for this issue.  X86_64 actually is using move_native_irq.
    
    Signed-off-by: Shaohua Li <shaohua.li@intel.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>


Regards,
-Dimitri Puzin aka Tristan-777