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Re: [PATCH] Linux Kernel Markers
- From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
- To: Karim Yaghmour <karim at opersys dot com>
- Cc: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Martin Bligh <mbligh at google dot com>, prasanna at in dot ibm dot com, Andrew Morton <akpm at osdl dot org>, "Frank Ch. Eigler" <fche at redhat dot com>, Ingo Molnar <mingo at elte dot hu>, Paul Mundt <lethal at linux-sh dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, Jes Sorensen <jes at sgi dot com>, Tom Zanussi <zanussi at us dot ibm dot com>, Richard J Moore <richardj_moore at uk dot ibm dot com>, Michel Dagenais <michel dot dagenais at polymtl dot ca>, Christoph Hellwig <hch at infradead dot org>, Greg Kroah-Hartman <gregkh at suse dot de>, Thomas Gleixner <tglx at linutronix dot de>, William Cohen <wcohen at redhat dot com>, ltt-dev at shafik dot org, systemtap at sources dot redhat dot com, Alan Cox <alan at lxorguk dot ukuu dot org dot uk>
- Date: Wed, 20 Sep 2006 13:15:54 -0400
- Subject: Re: [PATCH] Linux Kernel Markers
- References: <4510151B.5070304@google.com> <20060919093935.4ddcefc3.akpm@osdl.org> <45101DBA.7000901@google.com> <20060919063821.GB23836@in.ibm.com> <45102641.7000101@google.com> <20060919070516.GD23836@in.ibm.com> <451030A6.6040801@google.com> <45105B5E.9080107@opersys.com> <451141B1.40803@hitachi.com> <451178B0.9030205@opersys.com>
* Karim Yaghmour (karim@opersys.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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