linux-kernel - [tip:core/urgent] rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf

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Date:	Thu, 4 Mar 2010 16:33:07 GMT
From:	"tip-bot for Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
	hpa@...or.com, mingo@...hat.com, fweisbec@...il.com,
	rostedt@...dmis.org, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:core/urgent] rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf_prepare()

Commit-ID:  8d53dd546f36073e0d29b0cfc24c665db301e3e7
Gitweb:     http://git.kernel.org/tip/8d53dd546f36073e0d29b0cfc24c665db301e3e7
Author:     Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
AuthorDate: Wed, 3 Mar 2010 17:50:18 -0800
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 4 Mar 2010 12:07:35 +0100

rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf_prepare()

Change the pair of rcu_dereference() calls in
ftrace_perf_buf_prepare() to rcu_dereference_sched().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Acked-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: laijs@...fujitsu.com
Cc: dipankar@...ibm.com
Cc: mathieu.desnoyers@...ymtl.ca
Cc: josh@...htriplett.org
Cc: dvhltc@...ibm.com
Cc: niv@...ibm.com
Cc: peterz@...radead.org
Cc: Valdis.Kletnieks@...edu
Cc: dhowells@...hat.com
Cc: Frederic Weisbecker <fweisbec@...il.com>
LKML-Reference: <1267667418-32233-3-git-send-email-paulmck@...ux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 include/trace/ftrace.h             |    4 ++--
 kernel/trace/trace_event_profile.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 0804cd5..601ad77 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -699,9 +699,9 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
  *	__cpu = smp_processor_id();
  *
  *	if (in_nmi())
- *		trace_buf = rcu_dereference(perf_trace_buf_nmi);
+ *		trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
  *	else
- *		trace_buf = rcu_dereference(perf_trace_buf);
+ *		trace_buf = rcu_dereference_sched(perf_trace_buf);
  *
  *	if (!trace_buf)
  *		goto end;
diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index f0d6930..c1cc3ab 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -138,9 +138,9 @@ __kprobes void *ftrace_perf_buf_prepare(int size, unsigned short type,
 	cpu = smp_processor_id();
 
 	if (in_nmi())
-		trace_buf = rcu_dereference(perf_trace_buf_nmi);
+		trace_buf = rcu_dereference_sched(perf_trace_buf_nmi);
 	else
-		trace_buf = rcu_dereference(perf_trace_buf);
+		trace_buf = rcu_dereference_sched(perf_trace_buf);
 
 	if (!trace_buf)
 		goto err;
--
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