Re: latest -git: WARNING: at arch/x86/kernel/ipi.c:123 send_IPI_mask_bitmask+0xc3/0xe0()

["H. Peter Anvin" <hpa@kernel.org>]

Vegard Nossum wrote:
> 
> Hm.
> 
> Kernel fails to detect cpu1 at all.
> 
> I am currently unsure of whether it's your patch or not. But it's the
> same config that I've been booting for ages (and I copy it over for
> each new kernel version I check out).
> 
> Processor #0 (Bootup-CPU)
> I/O APIC #2 Version 32 at 0xFEC00000.
> Enabling APIC mode:  Flat.  Using 1 I/O APICs
> Processors: 1
> SMP: Allowing 1 CPUs, 0 hotplug CPUs
> mapped APIC to ffffb000 (fee00000)
> mapped IOAPIC to ffffa000 (fec00000)
> Allocating PCI resources starting at 50000000 (gap: 40000000:bee00000)
> PERCPU: Allocating 1221764 bytes of per cpu data
> NR_CPUS: 7, nr_cpu_ids: 1, nr_node_ids 1
> 
> I really don't get it. Is this something that can be caused by your
> patch _at all_ ?
> 

Well, if smp_call_function_single() is called during the CPU up 
sequence, without the CPU having been added to the online mask, then 
yes, it could.  The most likely place would be from a notifier.

That makes it ugly.  Need to track down the reason.

	-hpa