linux-kernel - Re: [patch 04/11] Introduce virtual debug register in thread_struct and wrapper-routines around process related functions

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Message-ID: <20090310143543.GE3850@elte.hu>
Date:	Tue, 10 Mar 2009 15:35:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	prasad@...ux.vnet.ibm.com
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [patch 04/11] Introduce virtual debug register in
	thread_struct and wrapper-routines around process related functions


* prasad@...ux.vnet.ibm.com <prasad@...ux.vnet.ibm.com> wrote:

> This patch introduces virtual debug registers to used by the 
> per-thread structure ad wrapper routines to manage debug 
> registers by process-related functions.

this is somewhat confusing. It would be much clearer to name it 
'user debug registers'.
  
and why is this:

> @@ -427,13 +427,9 @@ struct thread_struct {
>  	unsigned long		ip;
>  	unsigned long		fs;
>  	unsigned long		gs;
> -	/* Hardware debugging registers: */
> -	unsigned long		debugreg0;
> -	unsigned long		debugreg1;
> -	unsigned long		debugreg2;
> -	unsigned long		debugreg3;
> -	unsigned long		debugreg6;
> -	unsigned long		debugreg7;
> +	/* Hardware breakpoint info */
> +	unsigned long	vdr6;
> +	struct thread_hw_breakpoint	*hw_breakpoint_info;

detached from thread_struct? There's a lot of complications 
(alloc/free, locking, etc.) from this for no good reason - the 
hardware-breakpoints info structure is alway per thread and is 
quite small, so there's no reason not to embedd it directly 
inside thread_struct.

That way we get its allocation and freeing logic for free in 
essence.

	Ingo
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