Messages in this thread | | | Date | Sun, 20 Sep 2009 20:21:24 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: Don't ack_APIC_irq() if lapic is disabled in GENERIC_INTERRUPT_VECTOR handler |
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* Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> [Ingo Molnar - Sun, Sep 20, 2009 at 08:06:32PM +0200] > | > | * Sheng Yang <sheng@linux.intel.com> wrote: > | > | > Otherwise would cause trouble... > | > > | > Cc: Dimitri Sivanich <sivanich@sgi.com> > | > Signed-off-by: Sheng Yang <sheng@linux.intel.com> > | > --- > | > arch/x86/kernel/irq.c | 3 ++- > | > 1 files changed, 2 insertions(+), 1 deletions(-) > | > > | > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > | > index b0cdde6..78b23d0 100644 > | > --- a/arch/x86/kernel/irq.c > | > +++ b/arch/x86/kernel/irq.c > | > @@ -257,7 +257,8 @@ void smp_generic_interrupt(struct pt_regs *regs) > | > { > | > struct pt_regs *old_regs = set_irq_regs(regs); > | > > | > - ack_APIC_irq(); > | > + if (!disable_apic) > | > + ack_APIC_irq(); > | > | Wont in that case the apic->ack method be a NOP? > | > | Ingo > | > > iirc it was Xen related patch. So it's not that simple. > > I've pointed out Sheng about disable_apic. I'm not Xen > specialist but Xen team seem to use specific apic setup > so our "dummy" operations are not involved (case they > set disable_apic=1 without "turn off" apic ops in real). > Something like that.
They should then set a NOP function in that case. We really dont want to slow down hotpath functions like smp_generic_interrupt() with flaggery.
Ingo
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