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From: Thomas Gleixner <tglx@linutronix.de>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Kanaka Juvva <kanaka.d.juvva@linux.intel.com>,
	glenn.p.williamson@intel.com, matt.fleming@intel.com,
	will.auld@intel.com, Andi Kleen <andi@firstfloor.org>,
	ananth.s.narayan@intel.com, LKML <linux-kernel@vger.kernel.org>,
	andrew.j.herdrich@intel.com, Tony Luck <tony.luck@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org, mingo@redhat.com,
	"H. Peter Anvin" <hpa@zytor.com>,
	luto@amacapital.net, dvlasenk@redhat.com, bp@alien8.de,
	peter.p.waskiewicz.jr@intel.com, 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
Date: Thu, 18 Jun 2015 22:09:31 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.11.1506182201200.4107@nanos> (raw)
In-Reply-To: <5583234E.5080807@linux.intel.com>

On Thu, 18 Jun 2015, Dave Hansen wrote:
> 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?

Dunno. I did not test that stuff.

The might_sleep() in mutex_lock() should catch it as well, IF that
code was ever executed AFTER boot on a running system.

Thanks,

	tglx

  reply	other threads:[~2015-06-18 20:09 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-18 18:49 Kanaka Juvva
2015-06-18 19:47 ` Thomas Gleixner
2015-06-18 20:00   ` Dave Hansen
2015-06-18 20:09     ` Thomas Gleixner [this message]
2015-06-23 20:32   ` Vikas Shivappa

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