linux-kernel - Re: [PATCH v1 2/2] x86, perf,cqm: handle CPU hotplug

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Date:	Thu, 18 Jun 2015 13:00:14 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Kanaka Juvva <kanaka.d.juvva@...ux.intel.com>
CC:	kanaka.d.juvva@...el.com, glenn.p.williamson@...el.com,
	matt.fleming@...el.com, will.auld@...el.com, andi@...stfloor.org,
	ananth.s.narayan@...el.com, linux-kernel@...r.kernel.org,
	andrew.j.herdrich@...el.com, tony.luck@...el.com,
	peterz@...radead.org, x86@...nel.org, mingo@...hat.com,
	hpa@...or.com, luto@...capital.net, dvlasenk@...hat.com,
	bp@...en8.de, peter.p.waskiewicz.jr@...el.com, imammedo@...hat.com,
	bp@...e.de, ross.zwisler@...ux.intel.com, jacob.w.shin@...il.com,
	dirk.j.brandewie@...el.com, vikas.shivappa@...el.com,
	edwin.verplanke@...el.com, tomasz.kantecki@...el.com
Subject: Re: [PATCH v1 2/2] x86, perf,cqm: handle CPU hotplug

On 06/18/2015 12:47 PM, Thomas Gleixner wrote:
>> > @@ -1239,12 +1239,15 @@ static inline void cqm_pick_event_reader(int cpu)
>> >  	int phys_id = topology_physical_package_id(cpu);
>> >  	int i;
>> >  
>> > +	mutex_lock(&cache_mutex);
> I already explained it to Vikas. You CANNOT take a mutex in that code
> path as it runs with interrupts disabled on a CPU which cannot
> schedule.

How did lockdep not blow up and scream about this?
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