linux-kernel - Re: [PATCH] Linux Kernel Markers

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Message-ID: <20060920171554.GB18333@Krystal>
Date:	Wed, 20 Sep 2006 13:15:54 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Karim Yaghmour <karim@...rsys.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Martin Bligh <mbligh@...gle.com>, prasanna@...ibm.com,
	Andrew Morton <akpm@...l.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Paul Mundt <lethal@...ux-sh.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Jes Sorensen <jes@....com>, Tom Zanussi <zanussi@...ibm.com>,
	Richard J Moore <richardj_moore@...ibm.com>,
	Michel Dagenais <michel.dagenais@...ymtl.ca>,
	Christoph Hellwig <hch@...radead.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	William Cohen <wcohen@...hat.com>, ltt-dev@...fik.org,
	systemtap@...rces.redhat.com, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] Linux Kernel Markers

* Karim Yaghmour (karim@...rsys.com) wrote:
> 
> Masami Hiramatsu wrote:
> > This method is very similar to the djprobe.
> > And I had gotten the same idea to support preemptive kernel.
> ...
> > This means the below code, doesn't this?
> > ---
> > 	jmp 1f /* short jump consumes 2 bytes */
> > 	nop
> > 	nop
> > 	nop
> > 1:
> 
> Actually this is slightly different (and requires more support
> on behalf of the underlying mechanism then what I was suggesting.)
> Basically, as was discussed elsewhere, there is some complex
> mechanisms required for taking care of the case where you got
> an interrupt at, say, the second or third nop. With the
> mechanism I'm suggesting (replacing a 5 byte jmp with a 5 byte
> jmp), the underlying mechanics do not require having to take
> care of the above-mentioned case.
> 

Karim, the jmp already there targets the end of the region : no possible
executioni of the three following nops. Clever :)

Mathieu

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