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Date: Thu, 18 Jun 2015 13:00:14 -0700
From: Dave Hansen <dave.hansen@linux.intel.com>
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To: Thomas Gleixner <tglx@linutronix.de>,
        Kanaka Juvva <kanaka.d.juvva@linux.intel.com>
CC: kanaka.d.juvva@intel.com, glenn.p.williamson@intel.com,
        matt.fleming@intel.com, will.auld@intel.com, andi@firstfloor.org,
        ananth.s.narayan@intel.com, linux-kernel@vger.kernel.org,
        andrew.j.herdrich@intel.com, tony.luck@intel.com, peterz@infradead.org,
        x86@kernel.org, mingo@redhat.com, hpa@zytor.com, luto@amacapital.net,
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        imammedo@redhat.com, bp@suse.de, ross.zwisler@linux.intel.com,
        jacob.w.shin@gmail.com, dirk.j.brandewie@intel.com,
        vikas.shivappa@intel.com, edwin.verplanke@intel.com,
        tomasz.kantecki@intel.com
Subject: Re: [PATCH v1 2/2] x86, perf,cqm: handle CPU hotplug
References: <1434653369-5162-1-git-send-email-kanaka.d.juvva@linux.intel.com> <alpine.DEB.2.11.1506182146160.4107@nanos>
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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?