linux-kernel - [PATCH RFC v5 3/6] srcu: Add notrace variant of srcu

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Date:   Mon, 30 Apr 2018 18:42:01 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Fernandes <joelaf@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zilstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Boqun Feng <boqun.feng@...il.com>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Fenguang Wu <fengguang.wu@...el.com>,
        Baohong Liu <baohong.liu@...el.com>,
        Vedang Patel <vedang.patel@...el.com>, kernel-team@...roid.com
Subject: [PATCH RFC v5 3/6] srcu: Add notrace variant of srcu_dereference

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@...dmis.org>
Cc: Peter Zilstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Thomas Glexiner <tglx@...utronix.de>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Randy Dunlap <rdunlap@...radead.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Fenguang Wu <fengguang.wu@...el.com>
Cc: Baohong Liu <baohong.liu@...el.com>
Cc: Vedang Patel <vedang.patel@...el.com>
Cc: kernel-team@...roid.com
Signed-off-by: Joel Fernandes <joelaf@...gle.com>
---
 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.
-- 
2.17.0.441.gb46fe60e1d-goog