linux-kernel - Re: [RFC Patch 2/4] Allow breakpoints to be enabled/disabled without yielding the breakpoint request through new APIs

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Message-ID: <20091029213440.GA4596@in.ibm.com>
Date:	Fri, 30 Oct 2009 03:04:40 +0530
From:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC Patch 2/4] Allow breakpoints to be enabled/disabled
	without yielding the breakpoint request through new APIs -
	<enable><disable>_hw_breakpoint()

On Wed, Oct 28, 2009 at 04:31:49PM -0400, Steven Rostedt wrote:
> On Tue, 2009-10-27 at 02:49 +0530, K.Prasad wrote:
> 
> > Index: linux-2.6-tip.perf_hbkpt/include/asm-generic/hw_breakpoint.h
> > ===================================================================
> > --- linux-2.6-tip.perf_hbkpt.orig/include/asm-generic/hw_breakpoint.h
> > +++ linux-2.6-tip.perf_hbkpt/include/asm-generic/hw_breakpoint.h
> > @@ -102,11 +102,22 @@
> >   * ----------------------------------------------------------------------
> >   */
> >  struct hw_breakpoint {
> > +	/*
> > +	 * Denotes if a breakpoint is currently enabled in physical debug
> > +	 * registers. Not to be set directly by the end-user. Must be
> > +	 * operated through <enable><disable>_hw_breakpoint() APIs only.
> > +	 */
> > +	atomic_t enabled;
> 
> Just a nit, but by looking at this structure as a whole, it's not easy
> to see that the above comment is talking just about the "enabled" part
> of the structure or the entire structure itself.
> 
> Probably want to add ...
> 
> 	/*
> 	 * The enabled item denotes if ...
> 
> 
> -- Steve
>

I will modify the comments to read as under...the role of the 'enabled'
flag has undergone changes and the comments will reflect that.


 struct hw_breakpoint {
+	/*
+	 * The 'enabled' flag denotes if a breakpoint hit would in-turn invoke
+	 * the 'triggered' function. Not to be set directly by the end-user.
+	 * Must be operated through <enable><disable>_hw_breakpoint() APIs only.
+	 */
+	atomic_t enabled;
 	void (*triggered)(struct hw_breakpoint *, struct pt_regs *);
 	const cpumask_t *cpumask;
 	struct arch_hw_breakpoint info;

Thanks,
K.Prasad

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