linux-kernel - Re: 2.6.26-rt1

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Date:	Wed, 13 Aug 2008 15:30:32 +0200
From:	Juergen Beisert <jbe@...gutronix.de>
To:	linux-rt-users@...r.kernel.org, paulmck@...ux.vnet.ibm.com
Cc:	Jürgen Mell <j.mell@...nline.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	Clark Williams <williams@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Carsten Emde <ce@...g.ch>
Subject: Re: 2.6.26-rt1

On Freitag, 1. August 2008, Paul E. McKenney wrote:
> On Wed, Jul 30, 2008 at 11:01:32AM +0200, Jürgen Mell wrote:
> > On Wednesday, 30. July 2008, Thomas Gleixner wrote:
> > > We are pleased to announce the 2.6.26-rt1 tree, which can be
> > > downloaded from the location:
> >
> > I have tried the new kernel and have some good news and some bad news:
> >
> > The good news: The machine boots and seems to run without major problems.
> >
> > The bad news: It produces continuously lots of bug messages in the error
> > logs (cf. attached dmesg.tgz). The error at rtmutex.c:743 was already
> > present in 2.6.25-rt* when ACPI was enabled. The 'using smp_processor_id
> > ()  in preemptible code' is new here with 2.6.26.
> >
> > Machine is an old Athlon XP (single core) on an EPOX mainboard with VIA
> > chipset.
> >
> > If I can help with testing, please let me know.
>
> The following patch should clear things up.  It is against 2.6.25.8-rt7,
> but should still apply.
>
> ------------------------------------------------------------------------
>
> Disable preemption around statistics for RCU boost and unboost calls.
>
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
>
>  rcupreempt-boost.c |   20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff -urpNa -X dontdiff linux-2.6.25.8-rt7/kernel/rcupreempt-boost.c
> linux-2.6.25.8-rt7-preemptfix/kernel/rcupreempt-boost.c ---
> linux-2.6.25.8-rt7/kernel/rcupreempt-boost.c	2008-06-24 14:14:52.000000000
> -0700 +++
> linux-2.6.25.8-rt7-preemptfix/kernel/rcupreempt-boost.c	2008-06-24
> 14:38:59.000000000 -0700 @@ -205,11 +205,23 @@
> RCU_BOOST_TRACE_FUNC_DECL(boost_readers)
>  RCU_BOOST_TRACE_FUNC_DECL(try_unboost_readers)
>  RCU_BOOST_TRACE_FUNC_DECL(unboost_readers)
>  RCU_BOOST_TRACE_FUNC_DECL(over_taken)
> +static void rcu_trace_boost_boost_called_preempt(void)
> +{
> +	preempt_disable();
> +	rcu_trace_boost_boost_called(RCU_BOOST_ME);
> +	preempt_enable();
> +}
> +static void rcu_trace_boost_unboost_called_preempt(void)
> +{
> +	preempt_disable();
> +	rcu_trace_boost_unboost_called(RCU_BOOST_ME);
> +	preempt_enable();
> +}
>  #else /* CONFIG_RCU_TRACE */
>  /* These were created by the above macro "RCU_BOOST_TRACE_FUNC_DECL" */
> -# define rcu_trace_boost_task_boost_called(rbd) do { } while (0)
> +# define rcu_trace_boost_task_boost_called_preempt(rbd) do { } while (0)
>  # define rcu_trace_boost_task_boosted(rbd) do { } while (0)
> -# define rcu_trace_boost_boost_called(rbd) do { } while (0)
> +# define rcu_trace_boost_boost_called_preempt(rbd) do { } while (0)
>  # define rcu_trace_boost_try_boost(rbd) do { } while (0)
>  # define rcu_trace_boost_boosted(rbd) do { } while (0)
>  # define rcu_trace_boost_unboost_called(rbd) do { } while (0)
> @@ -261,7 +273,7 @@ void __rcu_preempt_boost(void)
>
>  	WARN_ON(!current->rcu_read_lock_nesting);
>
> -	rcu_trace_boost_boost_called(RCU_BOOST_ME);
> +	rcu_trace_boost_boost_called_preempt();
>
>  	/* check to see if we are already boosted */
>  	if (unlikely(rcu_is_boosted(curr)))
> @@ -313,7 +325,7 @@ void __rcu_preempt_unboost(void)
>  	int prio;
>  	unsigned long flags;
>
> -	rcu_trace_boost_unboost_called(RCU_BOOST_ME);
> +	rcu_trace_boost_unboost_called_preempt();
>
>  	/* if not boosted, then ignore */
>  	if (likely(!rcu_is_boosted(curr)))
>
Using this patch on top of 2.6.26-rt1 results into:

[...]
 CC      kernel/rcupreempt-boost.o
kernel/rcupreempt-boost.c: In function 'rcu_boost_task':
kernel/rcupreempt-boost.c:249: error: implicit declaration of function 'rcu_trace_boost_task_boost_called'
kernel/rcupreempt-boost.c: In function '__rcu_preempt_unboost':
kernel/rcupreempt-boost.c:328: error: implicit declaration of function 'rcu_trace_boost_unboost_called_preempt'

when CONFIG_PREEMPT_RCU_BOOST is enabled and target is a PowerPC of
type MPC5200B.

jbe

-- 
Dipl.-Ing. Juergen Beisert | http://www.pengutronix.de
 Pengutronix - Linux Solutions for Science and Industry
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