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From: Ananth N Mavinakayanahalli <>
To: Masami Hiramatsu <>
Cc: Abhishek Sagar <>,
	LKML <>,, Ingo Molnar <>
Subject: Re: [PATCH 0/3][RFC] x86: Catch stray non-kprobe breakpoints
Date: Wed, 30 Jan 2008 09:37:13 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jan 29, 2008 at 02:29:41PM -0500, Masami Hiramatsu wrote:
> Abhishek Sagar wrote:
> > On 1/29/08, Masami Hiramatsu <> wrote:
> >> In that case, why don't you just reduce the priority of kprobe_exceptions_nb?
> >> Then, the execution path becomes very simple.
> > 
> > Ananth mentioned that the kprobe notifier has to be the first to run.
> (Hmm.. I think he has just explained current implementation:))
> IMHO, since kprobes itself can not know what the external debugger
> wants to do, the highest priority should be reserved for those external tools.

The reason why kprobes needs to be the first to run is simple: it
doesn't need user intervention and if it isn't the intended recepient of
the breakpoint, it just lets the kernel take over (unlike a debugger,
which would potentially need user attention). Also, if the underlying
instruction itself is a breakpoint, we have the facility in kprobes to
single-step inline so the kernel can take control and notify any other
intended recepient of the underlying breakpoint.

As such, I believe the current situation is fine, has worked fine for
close to 4 years now and doesn't warrant any change.


      reply	other threads:[~2008-01-30  4:06 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-27  9:08 Abhishek Sagar
2008-01-29  6:02 ` Ananth N Mavinakayanahalli
2008-01-29 10:40   ` Abhishek Sagar
2008-01-29 13:18     ` Ananth N Mavinakayanahalli
2008-01-29 17:24       ` Abhishek Sagar
2008-01-29 15:13     ` Masami Hiramatsu
2008-01-29 18:08       ` Abhishek Sagar
2008-01-29 19:29         ` Masami Hiramatsu
2008-01-30  4:07           ` Ananth N Mavinakayanahalli [this message]

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