Re: [RFC] clustered apic irq affinity fix for i386

From: Andrew Morton (akpm@digeo.com)
Date: Wed Apr 30 2003 - 21:22:05 EST


Keith Mannthey <kmannth@us.ibm.com> wrote:
>
> This should be better. Thanks for the comments.

Remind me again what the patch actually does? It seems to be purely adding
debug checks?

Won't it just go BUG if someone boots the kernel and then tries to manually
set affinity?

Seems a bit racy too. setup_ioapic_dest() does:

                        pending_irq_balance_apicid[irq] = mask;
        ==> window here
                        set_ioapic_affinity(irq, mask);

ioapic_lock is not held, so there is a window where
pending_irq_balance_apicid[irq] can be set to some other value and
io_apic_write_affinity() will accidentally go BUG.

Is it not possible to fix set_ioapic_affinity() for real for clustered APIC
mode? What is involved in that?

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