linux-kernel - Re: [PATCH 2/6] hw_breakpoints: Migrate breakpoint conditional build under new config

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Date:	Tue, 5 Jul 2011 15:49:25 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Paul Mundt <lethal@...ux-sh.org>,
	linuxppc-dev@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 2/6] hw_breakpoints: Migrate breakpoint conditional build
 under new config

On Mon, Jul 04, 2011 at 11:14:16PM +0530, K.Prasad wrote:
> On Mon, Jul 04, 2011 at 03:29:14PM +0200, Frederic Weisbecker wrote:
> > On Mon, Jul 04, 2011 at 06:57:46PM +0530, K.Prasad wrote:
> > > On Tue, May 24, 2011 at 11:52:23PM +0200, Frederic Weisbecker wrote:
> > > > Migrate conditional hw_breakpoint code compilation under
> > > > the new config to prepare for letting the user chose whether
> > > > or not to build this feature
> > > > 
> > > 
> > > Making the hardware breakpoint patches modular has always been a goal.
> > > I've looked at the PowerPC parts of the code and they look harmless.
> > > 
> > > Acked-by: K.Prasad <prasad@...ux.vnet.ibm.com>
> > 
> > Great!
> > 
> > I'll push that soon, thanks guys for your acks!
> 
> Meanwhile, I was testing hardware breakpoints through perf and found
> that monitoring a given address fails when using 'perf record' (returns
> -ENOSPC) while 'perf stat' and watchpoint through gdb works fine (see
> logs below).
> 
> Has this behaviour been reported for other perf counters?

Nope I haven't anything like that. What I reported privately to you a
few ago was actually due to a mistake of mine. Otherwise I haven't seen
other problems.

-ENOSPC is likely related to the breakpoint slot reservation, in kernel/events/hw_breakpoint.c
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