[tip:core/urgent] rcu, ftrace: Fix RCU lockdep splat in ftrace_perf_buf_prepare()

tip-bot for Paul E. McKenney
2010-03-04T16:33:41Z

Commit-ID: 8d53dd546f36073e0d29b0cfc24c665db301e3e7
Gitweb: http://git.kernel.org/tip/8d53dd546f36073e0d29b0cfc24c665db301e3e7
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Wed, 3 Mar 2010 17:50:18 -0800
Committer: Ingo Molnar <mingo@elte.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@linux.vnet.ibm.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1267667418-32233-3-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.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;