linux-kernel - Re: [PATCH V2] perf/x86: Consider pinned events for group validation

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Date:   Fri, 23 Aug 2019 04:05:12 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <ak@...ux.intel.com>
cc:     kan.liang@...ux.intel.com, peterz@...radead.org, mingo@...hat.com,
        acme@...nel.org, linux-kernel@...r.kernel.org, eranian@...gle.com
Subject: Re: [PATCH V2] perf/x86: Consider pinned events for group
 validation

On Thu, 22 Aug 2019, Andi Kleen wrote:
> On Thu, Aug 22, 2019 at 08:29:46PM +0200, Thomas Gleixner wrote:
> > On Thu, 22 Aug 2019, Andi Kleen wrote:
> > 
> > > > +	/*
> > > > +	 * Disable interrupts to prevent the events in this CPU's cpuc
> > > > +	 * going away and getting freed.
> > > > +	 */
> > > > +	local_irq_save(flags);
> > > 
> > > I believe it's also needed to disable preemption. Probably should
> > > add a comment, or better an explicit preempt_disable() too.
> > 
> > Preemption is implicit disabled by disabling interrupts.
> 
> Yes it is, this is more for documentation.

Comment, yes. An explicit preempt_disable() surely not.

Thanks,

	tglx