Hi,
On Thu, Mar 17, 2016 at 7:39 PM, Thomas Gleixner <t...@linutronix.de> wrote:
> B1;2802;0cOn Thu, 17 Mar 2016, Peter Zijlstra wrote:
>
>> On Thu, Mar 17, 2016 at 11:21:24AM +0100, Thomas Gleixner wrote:
>> > On Thu, 17 Mar 2016, Peter Zijlstra wrote:
>> >
>> > > Could you please try? I'm not sure how this would explain your loop
>> > > device bug fail, but it certainly pointed towards broken.
>> >
>> > It definitely does not explain it. The wreckage that topo stuff causes is
>> > that
>> > it disables a cpu, but that really is not a reason for block/loop to
>> > explode.
>>
>> Right. Sadly I could not reproduce that error on my machine. But we can
>> at least start by fixing the 'obvious' problems and then maybe we get
>> more clues ;-)
>
> I'm able to reproduce by rejecting a cpu in that topology map function
> forcefully.
>
> That stuff explodes, because the block-mq code assumes that cpu_possible_mask
> has no holes.
>
> #define queue_for_each_ctx(q, ctx, i) \
> for ((i) = 0; (i) < (q)->nr_queues && \
> ({ ctx = per_cpu_ptr((q)->queue_ctx, (i)); 1; }); (i)++)
>
> is what makes that assumption about a consecutive possible mask.
>
> The cure for now is the patch below on top of PeterZ's patch.
No panic with both Peter's patch and yours.
Thanks all.
--
Xiong
>
> But we have to clarify and document whether holes in cpu_possible_mask are not
> allowed at all or if code like the above is simply broken.
>
> Thanks,
>
> tglx
> ---
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 643dbdccf4bc..f2ed8a01f870 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -345,7 +345,6 @@ static void __init smp_init_package_map(void)
> continue;
> pr_warn("CPU %u APICId %x disabled\n", cpu, apicid);
> per_cpu(x86_bios_cpu_apicid, cpu) = BAD_APICID;
> - set_cpu_possible(cpu, false);
> set_cpu_present(cpu, false);
> }
> }
>
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>
