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>

2 files changed, 4 insertions, 4 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 0804cd594803..601ad7744247 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 f0d693005075..c1cc3ab633de 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;