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From:   Joel Fernandes <joelaf@google.com>
To:     linux-kernel@vger.kernel.org
Cc:     kernel-team@android.com,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Boqun Feng <boqun.feng@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Erick Reyes <erickreyes@google.com>,
        Ingo Molnar <mingo@redhat.com>,
        Julia Cartwright <julia@ni.com>,
        linux-kselftest@vger.kernel.org,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Shuah Khan <shuah@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Glexiner <tglx@linutronix.de>,
        Todd Kjos <tkjos@google.com>,
        Tom Zanussi <tom.zanussi@linux.intel.com>
Subject: [PATCH v7 3/8] srcu: Add notrace variant of srcu_dereference
Date:   Wed, 23 May 2018 18:21:52 -0700
Message-Id: <20180524012157.181277-4-joel@joelfernandes.org>
In-Reply-To: <20180524012157.181277-1-joel@joelfernandes.org>
References: <20180524012157.181277-1-joel@joelfernandes.org>
Sender: linux-kernel-owner@vger.kernel.org
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From: "Joel Fernandes (Google)" <joel@joelfernandes.org>

In the last patch in this series, we are making lockdep register hooks
onto the irq_{disable,enable} tracepoints. These tracepoints use the
_rcuidle tracepoint variant. In this series we switch the _rcuidle
tracepoint callers to use SRCU instead of sched-RCU. Inorder to
dereference the pointer to the probe functions, we could call
srcu_dereference, however this API will call back into lockdep to check
if the lock is held *before* the lockdep probe hooks have a chance to
run and annotate the IRQ enabled/disabled state.

For this reason we need a notrace variant of srcu_dereference since
otherwise we get lockdep splats. This patch adds the needed
srcu_dereference_notrace variant.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 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