linux-kernel - Re: [PATCH v2] tracing/function-graph-tracer: prevent from hrtimer interrupt infinite loop

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Message-ID: <20081218211637.GF24271@elte.hu>
Date:	Thu, 18 Dec 2008 22:16:37 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frédéric Weisbecker <fweisbec@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tracing/function-graph-tracer: prevent from hrtimer
	interrupt infinite loop


* Frédéric Weisbecker <fweisbec@...il.com> wrote:

> Hmm. No, I just tested by setting 1000 HZ and disabled NOHZ, the system 
> doesn't lockup unless I turn on the function graph tracer.

but that's what we are interested in: the system locks up with HZ=1000 and 
with the tracer on - right?

Which means that it's not some hrtimer problem, but simply the traced 
timer tick takes more than 1 millisecond to execute under this 
virtualization.

	Ingo
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