linux-kernel - Re: [BUG RT] 2.6.25.8-rt7 on 8-way

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Date:	Sun, 29 Jun 2008 16:28:44 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Noah Watkins <noahwatkins@...il.com>
Cc:	Sven-Thorsten Dietrich <sven@...bigcorporation.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	RT <linux-rt-users@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [BUG RT] 2.6.25.8-rt7 on 8-way

On Sun, Jun 29, 2008 at 06:18:46PM -0500, Noah Watkins wrote:
> That eliminated the messages.

Does the patch below allow you to re-enable CONFIG_PREEMPT_RCU_BOOST
without getting these messages?  (I sent this out previously, but
am to lazy to search for the original posting.)

						Thanx, Paul

> - Noah
> 
> On Sun, Jun 29, 2008 at 5:23 PM, Sven-Thorsten Dietrich
> <sven@...bigcorporation.com> wrote:
> > On Sun, 2008-06-29 at 16:32 -0500, Noah Watkins wrote:
> >> My kernel is very, very noisy with the following bug:
> >>
> >> - Full dmesg below
> >> - Please CC me
> >>
> >
> > I found this as well (adding Paul).
> >
> > If you disable CONFIG_PREEMPT_RCU_BOOST, does it go away?
> >
> > Regards,
> > Sven

Signed-off-by: Paul E. McKenney <paulmck@...ibm.com>
---

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)))
--
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