linux-kernel - Re: [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG

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Message-ID: <1264764648.4283.2231.camel@laptop>
Date:	Fri, 29 Jan 2010 12:30:48 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Fr??d??ric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>
Subject: Re: [PATCH tracing/kprobes] kprobes: Disable booster when
 CONFIG_PREEMPT=y

On Fri, 2010-01-29 at 10:21 +0100, Ingo Molnar wrote:
> * Masami Hiramatsu <mhiramat@...hat.com> wrote:
> 
> > Disable kprobe booster when CONFIG_PREEMPT=y, because it can't ensure that 
> > all kernel threads preempted on kprobe's boosted slot run out from the slot 
> > even using freeze_processes().
> 
> hm, this really sucks as it makes preemptible kernels perform worse. Is there 
> no better solution?

We could pre-allocate 1 slot per kernel thread.

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