linux-kernel - Re: [RFC][PATCH] KGDB: remove kgdb-own fault handling

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Message-ID: <47ACD4CB.7090701@windriver.com>
Date:	Fri, 08 Feb 2008 16:16:43 -0600
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Jan Kiszka <jan.kiszka@....de>, Andi Kleen <andi@...stfloor.org>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC][PATCH] KGDB: remove kgdb-own fault handling

Linus Torvalds wrote:
> On Fri, 8 Feb 2008, Jan Kiszka wrote:
>   
>> Well, let's try it this way: Find below a patch against kgdb.git that
>> removes the special fault handling (this wouldn't be the first feature I
>> recently removed from kgdb :->). Light testing revealed no obvious
>> problems yet.
>>     
>
> That is indeed horrible code. No way will I merge anything that has things 
> like that even in it's *history* (ie somebody needs to re-generate the 
> tree without code like that - some things should not be allowed to exist).
>
>   

I concur.  I will collapse the entire kgdb tree back to the original few
patches which can be bisected.

> That said, while just using "probe_kernel_addr()" is certainly much 
> better, it's still really inefficient. If you actually want to do a "safe 
> memory copy", then the right way to do that is basically to do
>
> 	pagefault_disable();
> 	leftover = __copy_from_user_inatomic(dst, src, count);
> 	pagefault_enable();
>
> 	if (leftover)
> 		handle_the_fact_that_the_copy_didnt_complete();
>
>   

Duly Noted.  Further cleanups are in progress.


Thanks,
Jason.
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