linux-kernel - Re: [PATCH 3/6] x86: Allow the user not to build hw

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Message-ID: <4DC020D9.3050000@zytor.com>
Date:	Tue, 03 May 2011 08:35:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jason Wessel <jason.wessel@...driver.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/6] x86: Allow the user not to build hw_breakpoints

On 04/27/2011 12:50 PM, Frederic Weisbecker wrote:
> On Wed, Apr 27, 2011 at 11:54:17AM -0700, H. Peter Anvin wrote:
>> Why do you have to be able to disable breakpoints to disable perf? That seems seriously backwards, especially since we had breakpoints long before perf...
> 
> That started when we implemented breakpoints as counters. Then we realized that
> ptrace had its own scheduling that was somehow duplicating what perf was doing.
> So we have finally unified that under perf. The good point is that archs don't need
> to care much about ptrace breakpoints tracking, just the interface.
> 
> But yeah the bad point is that dependency.

It really is very bad... without breakpoints, you lose almost all
debugging support.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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