Messages in this thread | | | Date | Fri, 28 Mar 2008 15:24:30 -0500 | From | Jack Steiner <> | Subject | Re: [PATCH 8/8] x86_64: Support for new UV apic |
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On Fri, Mar 28, 2008 at 09:15:32PM +0100, Ingo Molnar wrote: > > * Jack Steiner <steiner@sgi.com> wrote: > > > Index: linux/arch/x86/kernel/apic_64.c > > =================================================================== > > --- linux.orig/arch/x86/kernel/apic_64.c 2008-03-28 13:00:22.000000000 -0500 > > +++ linux/arch/x86/kernel/apic_64.c 2008-03-28 13:06:12.000000000 -0500 > > @@ -738,6 +738,7 @@ void __cpuinit setup_local_APIC(void) > > unsigned int value; > > int i, j; > > > > + preempt_disable(); > > value = apic_read(APIC_LVR); > > > > BUILD_BUG_ON((SPURIOUS_APIC_VECTOR & 0x0f) != 0x0f); > > @@ -831,6 +832,7 @@ void __cpuinit setup_local_APIC(void) > > else > > value = APIC_DM_NMI | APIC_LVT_MASKED; > > apic_write(APIC_LVT1, value); > > + preempt_enable(); > > } > > hm, this looks a bit weird - why are all the preempt-disable/enable > calls needed?
The first patch had a preempt disable/enable in the function that reads apicid (see read_apic_id() in arch/x86/kernel/genapic_64.c). This seemed necessary since large system generate an apicid by reading the live id & concatenating it with extra bits.
One of the review comments suggested that I change the preempt to a WARN() since reading apic_id really should be done with preemtion disabled. The added code eliminates the warnings.
--- jack
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