On Wed, 2012-03-07 at 11:48 -0800, Alok Kataria wrote:
> Len, anyone else,
>
> Any comments on this one ? This fixes a important bug during cpu hotadd
> where the kernel fails to recognize all the newly added cpus.
>
> Thanks,
> Alok
>
>
> On Wed, 2012-02-15 at 16:06 -0800, Petr Vandrovec wrote:
> > From: Petr Vandrovec <petr@xxxxxxxxxx>
> >
> > When processor is being hot-added to the system, acpi_map_lsapic invokes
> > ACPI _MAT method to find APIC ID and flags, verifies that returned structure
> > is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
> > bit. Then saves APIC ID, frees structure - and accesses structure when
> > computing arguments for acpi_register_lapic call. Which sometime leads
> > to acpi_register_lapic call being made with second argument zero, failing
> > to bring processor online with error 'Unable to map lapic to logical cpu
> > number'.
> >
> > As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
> > few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
> > acpi_register_lapic.
> >
> > Thanks, Petr
> >
> > Signed-off-by: Petr Vandrovec <petr@xxxxxxxxxx>
> > Signed-off-by: Alok Kataria <akataria@xxxxxxxxxx>
> >
> >
> > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
> > index ce664f3..a4a0901 100644
> > --- a/arch/x86/kernel/acpi/boot.c
> > +++ b/arch/x86/kernel/acpi/boot.c
> > @@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
> > goto free_tmp_map;
> >
> > cpumask_copy(tmp_map, cpu_present_mask);
> > - acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
> > + acpi_register_lapic(physid, ACPI_MADT_ENABLED);
The change looks good. I suggest you also add the following line to
prevent such bug in future.
kfree(buffer.pointer);
buffer.length = ACPI_ALLOCATE_BUFFER;
buffer.pointer = NULL;
+ lapic = NULL;
Thanks,
-Toshi
> >
> > /*
> > * If mp_register_lapic successfully generates a new logical cpu
>
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