linux-kernel - Re: [PATCH 09/10] x86/intel_rdt: Hot cpu support for Cache Allocation

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Date:	Tue, 16 Jun 2015 12:01:19 -0700 (PDT)
From:	Vikas Shivappa <vikas.shivappa@...el.com>
To:	Thomas Gleixner <tglx@...utronix.de>
cc:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, vikas.shivappa@...el.com,
	x86@...nel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, matt.fleming@...el.com, will.auld@...el.com,
	linux-rdt@...ists.intel.com
Subject: Re: [PATCH 09/10] x86/intel_rdt: Hot cpu support for Cache
 Allocation



On Tue, 16 Jun 2015, Thomas Gleixner wrote:

> On Fri, 12 Jun 2015, Vikas Shivappa wrote:
>> +static inline void intel_rdt_cpu_start(int cpu)
>> +{
>> +	struct intel_pqr_state *state = &per_cpu(pqr_state, cpu);
>> +
>> +	state->closid = 0;
>> +	mutex_lock(&rdt_group_mutex);
>
> This is called from CPU_STARTING, which runs on the starting cpu with
> interrupts disabled. Clearly never tested with any of the mandatory
> debug configs enabled.

But this can race with cbm_update_all calling on_each_cpu_mask ? or in other 
words the lock helps on_each_cpu_mask not race with hot cpu code updating the 
rdt_cpumask since the on_each_cpu_mask is also called with the lock always.

Its tested on the 0 day build which should include the debug config. Will add a 
tested tag.

Thanks,
Vikas

>
> Thanks
>
> 	tglx
>
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