linux-kernel - Re: [RFC][PATCH] kprobes: Add separate preempt

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Date:	Thu, 30 Jun 2011 23:56:37 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] kprobes: Add separate preempt_disabling for
 kprobes

On Thu, 2011-06-30 at 11:51 -0400, Steven Rostedt wrote:
> 
> To solve this, I've added a per_cpu variable called
> kprobe_preempt_disabled, that is set by the kprobe code. If it is set,
> the preempt_schedule() will not preempt the code.

Damn this is ugly. Can we step back and see if we can make the
requirement for kprobe to disable preemption go away?

Why does it have to do that anyway? Isn't it keeping enough per-task
state to allow preemption over the single step?


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