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Subject: Re: [REGRESSION][v4.14.y][v4.15] x86/intel_rdt/cqm: Improve limbo
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To:     Thomas Gleixner <tglx@linutronix.de>,
        "Yu, Fenghua" <fenghua.yu@intel.com>
Cc:     "Shankar, Ravi V" <ravi.v.shankar@intel.com>,
        "vikas.shivappa@linux.intel.com" <vikas.shivappa@linux.intel.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Luck, Tony" <tony.luck@intel.com>,
        "peterz@infradead.org" <peterz@infradead.org>,
        "eranian@google.com" <eranian@google.com>,
        "ak@linux.intel.com" <ak@linux.intel.com>,
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        "hpa@zytor.com" <hpa@zytor.com>, "x86@kernel.org" <x86@kernel.org>,
        "1733662@bugs.launchpad.net" <1733662@bugs.launchpad.net>,
        "Roderick W. Smith" <rod.smith@canonical.com>
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 <alpine.DEB.2.20.1801161909020.2366@nanos>
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 <alpine.DEB.2.20.1801161957510.2366@nanos>
From:   Joseph Salisbury <joseph.salisbury@canonical.com>
Message-ID: <85822005-a3e5-a8eb-32a0-1dacd3af9804@canonical.com>
Date:   Wed, 17 Jan 2018 17:16:53 -0500
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On 01/16/2018 01:59 PM, Thomas Gleixner wrote:
> On Tue, 16 Jan 2018, Yu, Fenghua wrote:
>>> From: Thomas Gleixner [mailto:tglx@linutronix.de]
>> 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