From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Andi Kleen <andi@firstfloor.org>,
2nddept-manager@sdl.hitachi.co.jp
Subject: Re: [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86_64 right now)
Date: Fri, 18 Feb 2011 00:34:43 +0900 [thread overview]
Message-ID: <4D5D4013.4070602@hitachi.com> (raw)
In-Reply-To: <1297948703.23343.907.camel@gandalf.stny.rr.com>
(2011/02/17 22:18), Steven Rostedt wrote:
> On Thu, 2011-02-17 at 21:37 +0900, Masami Hiramatsu wrote:
>
>> Oops! with this change, current kprobes might not be able to probe
>> the entry of functions, because that is always reserved by ftrace!
>> I think we need to have some new interface for replacing each other
>> safely...
>
> Good point. I suspect that this wont be ready till .40 anyway. When I
> get a chance to work more an this, I'll also include patches where if
> -mfentry is activated kprobes will just hook to the mcount caller
> instead. Or ftrace itself :)
Ah, that's a good idea! :) it could be done without -mfentry too.
But is that possible to modify just one mcount entry? I also worry
about the latency of enabling/disabling one entry.
BTW, without dynamic ftrace (no code modifying), I think we don't
need to reserve mcount code, because no one modifies it.
>
> I'm also working on making the function tracer a bit more flexible. That
> is, to let multiple clients control the dynamic trace instead of just
> one big global one.
Nice!
--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2011-02-17 15:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-09 20:02 [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86_64 right now) Steven Rostedt
2011-02-09 20:02 ` [RFC][PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
2011-02-09 20:02 ` [RFC][PATCH 2/4] ftrace: Add -mfentry to Makefile on function tracer Steven Rostedt
2011-02-09 20:28 ` Steven Rostedt
2011-02-09 21:22 ` H. Peter Anvin
2011-02-09 20:02 ` [RFC][PATCH 3/4] ftrace: Do not test frame pointers if -mfentry is used Steven Rostedt
2011-02-09 20:02 ` [RFC][PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64 Steven Rostedt
2011-02-10 2:38 ` [RFC][PATCH 0/4] ftrace: Use -mfentry when supported (this is for x86_64 right now) Masami Hiramatsu
2011-02-17 12:37 ` Masami Hiramatsu
2011-02-17 13:18 ` Steven Rostedt
2011-02-17 15:34 ` Masami Hiramatsu [this message]
2011-02-17 15:46 ` Steven Rostedt
2011-02-17 16:07 ` Masami Hiramatsu
2011-02-17 20:11 ` Steven Rostedt
2011-02-18 11:45 ` Masami Hiramatsu
2011-02-18 15:07 ` Steven Rostedt
2011-02-18 15:19 ` Mathieu Desnoyers
2011-02-18 20:10 ` Dominique Toupin
2011-02-18 20:36 ` Steven Rostedt
2011-02-18 21:45 ` Dominique Toupin
2011-02-18 22:39 ` Andi Kleen
2011-02-18 22:45 ` H. Peter Anvin
2011-02-18 23:02 ` Steven Rostedt
2011-02-19 5:07 ` Masami Hiramatsu
2011-02-19 5:10 ` hpas
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