[PATCH RFC v5 3/6] srcu: Add notrace variant of srcu_dereference

From: Joel Fernandes
Date: Mon Apr 30 2018 - 21:42:41 EST

In this series, we are making lockdep use an rcuidle tracepoint. For
this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats since lockdep hooks may not have run
yet. This patch adds the needed variant.

Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Peter Zilstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Thomas Glexiner <tglx@xxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Fenguang Wu <fengguang.wu@xxxxxxxxx>
Cc: Baohong Liu <baohong.liu@xxxxxxxxx>
Cc: Vedang Patel <vedang.patel@xxxxxxxxx>
Cc: kernel-team@xxxxxxxxxxx
Signed-off-by: Joel Fernandes <joelaf@xxxxxxxxxx>
include/linux/srcu.h | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 2ec618979b20..a1c4947be877 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -135,6 +135,11 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp)
#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)

+ * srcu_dereference_notrace - no tracing and no lockdep calls from here
+ */
+#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1)
* srcu_read_lock - register a new reader for an SRCU-protected structure.
* @sp: srcu_struct in which to register the new reader.