Message-ID: <47ACD4CB.7090701@windriver.com>
Date: Fri, 08 Feb 2008 16:16:43 -0600
From: Jason Wessel <jason.wessel@windriver.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Jan Kiszka <jan.kiszka@web.de>, Andi Kleen <andi@firstfloor.org>,
       Maxim Levitsky <maximlevitsky@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC][PATCH] KGDB: remove kgdb-own fault handling
References: <20080130011550.GA31853@elte.hu> <200802050436.31070.maximlevitsky@gmail.com> <alpine.LFD.1.00.0802041922300.3237@woody.linux-foundation.org> <p73ejbn2xk2.fsf@bingen.suse.de> <47AC95FC.5090701@siemens.com> <20080208185719.GA11573@one.firstfloor.org> <47ACC97C.3000806@web.de> <alpine.LFD.1.00.0802081347150.2896@woody.linux-foundation.org>
In-Reply-To: <alpine.LFD.1.00.0802081347150.2896@woody.linux-foundation.org>
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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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