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    SubjectCPU hotplug and IRQ affinity with 2.6.24-rt1
    This is just an FYI. As part of the "Isolated CPU extensions" thread Daniel suggest for me
    to check out latest RT kernels. So I did or at least tried to and immediately spotted a couple
    of issues.

    The machine I'm running it on is:
    HP xw9300, Dual Opteron, NUMA

    It looks like with -rt kernel IRQ affinity masks are ignored on that system. ie I write 1 to
    lets say /proc/irq/23/smp_affinity but the interrupts keep coming to CPU1.
    Vanilla 2.6.24 does not have that issue.

    Also the first thing I tried was to bring CPU1 off-line. Thats the fastest way to get irqs,
    soft-irqs, timers, etc of a CPU. But the box hung completely. It also managed to mess up my
    ext3 filesystem to the point where it required manual fsck (have not see that for a couple of
    years now).
    I tried the same thing (ie echo 0 > /sys/devices/cpu/cpu1/online) from the console. It hang
    again with the message that looked something like:
    CPU1 is now off-line
    Thread IRQ-23 is on CPU1 ...

    IRQ 23 is NVidia SATA. So I guess it has something to do with the borked affinity handling.
    Vanilla 2.6.24 handles this just fine.

    Anyway, like I said it's just an FYI, not an urgent issue.

    Max



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