linux-kernel - Re: [patch 02/11] x86 architecture implementation of Hardware Breakpoint interfaces

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Message-Id: <1237002033.25062.77.camel@pasglop>
Date:	Sat, 14 Mar 2009 14:40:33 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alan Stern <stern@...land.harvard.edu>, prasad@...ux.vnet.ibm.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [patch 02/11] x86 architecture implementation of Hardware
 Breakpoint interfaces

On Tue, 2009-03-10 at 18:26 +0100, Ingo Molnar wrote:
> 
> That 'arbitrarily larg number of breakpoints' worries me. It's a 
> pretty broken concept for a 4-items resource that cannot be 
> time-shared and hence cannot be overcommitted.
> 
> Seems to me that much of the complexity of this patchset:
> 
>  28 files changed, 2439 insertions(+), 199 deletions(-)
> 
> Could be eliminated via a very simple exclusive reservation 
> mechanism.
> 
I also have some worries about the bloat of this infrastructure,
especially in the context switching code.

I would prefer the arch to be in control of the state in the task struct
and just context switch the actual HW registers at that stage.

Ben.


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