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>

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 0804cd5948035d9dd8d59084e946c1d32cad330c..601ad7744247582feeec95555464ce4b8a2bdc0d 100644 (file)
--- 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 f0d693005075c938a7163e38f67171587814f0cc..c1cc3ab633de6cab14b87463d4f70669feb8904b 100644 (file)
--- 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;