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Date: Sun, 22 Mar 2009 21:41:56 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
       LKML <linux-kernel@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 0/5] [GIT PULL] updates for tip/tracing/ftrace
Message-ID: <20090322204156.GA27113@elte.hu>
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* Ingo Molnar <mingo@elte.hu> wrote:

> found another, unrelated lockup with the event tracer:
> 
> europe:/debug/tracing/events/sched/sched_wakeup_new> cat enable 
> 0
> europe:/debug/tracing/events/sched/sched_wakeup_new> echo 1 > enable
> europe:/debug/tracing/events/sched/sched_wakeup_new> sync
> europe:/debug/tracing/events/sched/sched_wakeup_new> cat 
> ../../../trace_pipe 
>            <...>-2870  [000]   688.730160: sched_wakeup_new: task 
> bash:2898 [120] success=1
>            <...>-2870  [001]   689.945375: sched_wakeup_new: task 
> bash:2899 [120] success=1
> 
> [hard lockup]

ok, tracked it down - it's the new trace_wake_up() from within 
wake_up_new_task() => bad idea.

I think this was introduced via:

6eaaa5d: tracing/core: use appropriate waiting on trace_pipe

	Ingo