linux-kernel - Re: [PATCH v3] tracing: Fix rcu splat from idle CPU on boot.

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Message-ID: <20151222144645.GA29103@breakpoint.cc>
Date:	Tue, 22 Dec 2015 15:46:49 +0100
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Philipp Schrader <philipp@...oton-tech.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
	paulmck@...ux.vnet.ibm.com, rostedt@...dmis.org
Subject: Re: [PATCH v3] tracing: Fix rcu splat from idle CPU on boot.

On 2015-12-14 11:07:09 [-0800], Philipp Schrader wrote:
> With PREEMPT_RT and most of the lockdep-related options enabled I
> encountered this splat when booting our DRA7 evaluation module:
> 
> [    0.055073]
> [    0.055076] ===============================
> [    0.055079] [ INFO: suspicious RCU usage. ]
> [    0.055084] 4.1.6+ #2 Not tainted
> [    0.055086] -------------------------------
> [    0.055090] include/trace/events/hist.h:31 suspicious
> rcu_dereference_check() usage!
…
> As per Steve Rotstedt's suggestion I changed the trace_* calls to
> trace_*_rcuidle calls. He pointed out that the trace points were getting
> triggered when rcu wasn't watching.
> 
> Signed-off-by: Philipp Schrader <philipp@...oton-tech.com>
> Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

I'm taking this for -RT. Is my assumption correct, that this goes into
the v4.5 merge window once everybody is back from holidays?

Sebastian
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