linux-kernel - Re: [PATCH 6/6] x86: Allow disabling HW_BREAKPOINTS and PERF

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Date:	Wed, 9 Oct 2013 08:02:28 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 6/6] x86: Allow disabling HW_BREAKPOINTS and PERF_EVENTS


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> On Tue, Oct 08, 2013 at 10:05:21PM +0200, Peter Zijlstra wrote:
> > On Tue, Oct 08, 2013 at 09:55:59PM +0200, Frederic Weisbecker wrote:
> > > 1) make breakpoints independant from perf. The drawback is that we must then
> > > add seperate hooks on context switch for ptrace breakpoints. OTOH we get
> > > rid of the perf -> breakpoint -> perf circular dependency, which is the very
> > > controversial thing.
> > 
> > we used to have this in __switch_to_xtra(), right?
> 
> Right.
> 
> And then it got replaced by perf events scheduling.

Which we have anyway - so this moved complexity out the contex switch 
path, for the common case where no hardware-breakpoints are used.

Thanks,

	Ingo
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