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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: 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>,
	Jason Wessel <jason.wessel@windriver.com>
Subject: Re: [RFC][PATCH] KGDB: remove kgdb-own fault handling (was: Re: [git pull] x86 arch updates for v2.6.25)
Date: Fri, 8 Feb 2008 13:58:44 -0800 (PST)	[thread overview]
Message-ID: <alpine.LFD.1.00.0802081347150.2896@woody.linux-foundation.org> (raw)
In-Reply-To: <47ACC97C.3000806@web.de>



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).

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();

which should even be reasonably efficient and should work in all contexts 
(hardware interrupts disabled, spinlocks held, you name it).

So all those "kgdb_{get|set}_mem()" things seem bogus (they also have 
insane calling semantics - return NULL or errptr? Why not just return an 
integer error code?

		Linus

  reply	other threads:[~2008-02-08 22:00 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-30  1:15 [git pull] x86 arch updates for v2.6.25 Ingo Molnar
2008-01-31  0:33 ` x86 arch updates also broke s390 Adrian Bunk
2008-01-31  9:34   ` Martin Schwidefsky
2008-01-31 10:24     ` Ingo Molnar
2008-01-31 12:37       ` Nick Piggin
2008-02-01  9:48     ` Ingo Molnar
2008-02-01  9:52       ` Ingo Molnar
2008-02-01  9:54       ` Martin Schwidefsky
2008-02-01 10:02         ` Ingo Molnar
2008-01-31 15:57 ` [git pull] x86 arch updates for v2.6.25 Adrian Bunk
2008-01-31 16:00   ` Ingo Molnar
2008-01-31 16:04     ` Ingo Molnar
2008-01-31 16:12     ` Adrian Bunk
2008-01-31 16:15       ` Ingo Molnar
2008-01-31 16:21         ` WANG Cong
2008-01-31 16:24         ` Adrian Bunk
2008-01-31 16:46           ` Ingo Molnar
2008-01-31 16:52             ` Jeremy Fitzhardinge
2008-01-31 16:29         ` sparc compile error caused by x86 arch updates Adrian Bunk
2008-01-31 16:50           ` Jeremy Fitzhardinge
2008-01-31 17:43             ` Ingo Molnar
2008-01-31 17:55               ` Jeremy Fitzhardinge
2008-01-31 18:21               ` Adrian Bunk
2008-01-31 18:38                 ` Ingo Molnar
2008-02-05  2:36 ` [git pull] x86 arch updates for v2.6.25 Maxim Levitsky
2008-02-05  3:27   ` Linus Torvalds
2008-02-05  4:11     ` Phil Oester
2008-02-05  4:54       ` Andrew Morton
2008-02-06 12:08         ` Jan Kiszka
2008-02-07 20:00           ` Daniel Phillips
2008-02-08  4:48       ` Christoph Hellwig
2008-02-08  9:51         ` Jan Kiszka
2008-02-05 17:45     ` John Stoffel
2008-02-05 17:52       ` H. Peter Anvin
2008-02-08 18:24         ` Bernhard Kaindl
2008-02-08 19:38           ` remote DMA via FireWire (was Re: [git pull] x86 arch updates for v2.6.25) Stefan Richter
2008-02-07 19:20     ` [git pull] x86 arch updates for v2.6.25 Daniel Phillips
2008-02-08 17:00     ` Andi Kleen
2008-02-08 17:48       ` Jan Kiszka
2008-02-08 18:57         ` Andi Kleen
2008-02-08 21:28           ` [RFC][PATCH] KGDB: remove kgdb-own fault handling (was: Re: [git pull] x86 arch updates for v2.6.25) Jan Kiszka
2008-02-08 21:58             ` Linus Torvalds [this message]
2008-02-08 22:16               ` [RFC][PATCH] KGDB: remove kgdb-own fault handling Jason Wessel
2008-02-09 14:11 ` [git pull] x86 arch updates for v2.6.25 Amit Shah
2008-02-10 12:30   ` Jiri Kosina
2008-02-12  7:16     ` Amit Shah
2008-02-13  8:56       ` Ingo Molnar
2008-02-13 10:19         ` Amit Shah

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