Re: [REGRESSION][v4.14.y][v4.15] x86/intel_rdt/cqm: Improve limbo list processing

From: Joseph Salisbury
Date: Wed Jan 17 2018 - 17:17:30 EST


On 01/16/2018 01:59 PM, Thomas Gleixner wrote:
> On Tue, 16 Jan 2018, Yu, Fenghua wrote:
>>> From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx]
>> Is this a Haswell specific issue?
>>
>> I run the following test forever without issue on Broadwell and 4.15.0-rc6 with rdt mounted:
>> for ((;;)) do
>> for ((i=1;i<88;i++)) do
>> echo 0 >/sys/devices/system/cpu/cpu$i/online
>> done
>> echo "online cpus:"
>> grep processor /proc/cpuinfo |wc
>> for ((i=1;i<88;i++)) do
>> echo 1 >/sys/devices/system/cpu/cpu$i/online
>> done
>> echo "online cpus:"
>> grep processor /proc/cpuinfo|wc
>> done
>>
>> I'm finding a Haswell to reproduce the issue.
> Come on. This is crystal clear from the KASAN trace. And the fix is simple enough.
>
> You simply do not run into it because on your machine
>
> is_llc_occupancy_enabled() is false...
>
> Thanks,
>
> tglx
>
> 8<--------------------
>
> diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
> index 88dcf8479013..99442370de40 100644
> --- a/arch/x86/kernel/cpu/intel_rdt.c
> +++ b/arch/x86/kernel/cpu/intel_rdt.c
> @@ -525,10 +525,6 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
> */
> if (static_branch_unlikely(&rdt_mon_enable_key))
> rmdir_mondata_subdir_allrdtgrp(r, d->id);
> - kfree(d->ctrl_val);
> - kfree(d->rmid_busy_llc);
> - kfree(d->mbm_total);
> - kfree(d->mbm_local);
> list_del(&d->list);
> if (is_mbm_enabled())
> cancel_delayed_work(&d->mbm_over);
> @@ -545,6 +541,10 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
> cancel_delayed_work(&d->cqm_limbo);
> }
>
> + kfree(d->ctrl_val);
> + kfree(d->rmid_busy_llc);
> + kfree(d->mbm_total);
> + kfree(d->mbm_local);
> kfree(d);
> return;
> }

Hi Thomas,

Testing of your patch shows that your patch resolves the bug. Thanks
for the assistance! Is this something you could submit to mainline?

Thanks,


Joe