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From: Joel Fernandes <joelaf@google.com>
To: linux-kernel@vger.kernel.org
Cc: "Joel Fernandes (Google)" <joel@joelfernandes.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zilstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Tom Zanussi <tom.zanussi@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Thomas Glexiner <tglx@linutronix.de>,
	Boqun Feng <boqun.feng@gmail.com>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Fenguang Wu <fengguang.wu@intel.com>,
	Baohong Liu <baohong.liu@intel.com>,
	Vedang Patel <vedang.patel@intel.com>,
	kernel-team@android.com
Subject: [PATCH RFC v6 2/5] srcu: Add notrace variant of srcu_dereference
Date: Mon,  7 May 2018 13:41:40 -0700	[thread overview]
Message-ID: <20180507204143.13061-3-joelaf@google.com> (raw)
In-Reply-To: <20180507204143.13061-1-joelaf@google.com>

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.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zilstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Glexiner <tglx@linutronix.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Fenguang Wu <fengguang.wu@intel.com>
Cc: Baohong Liu <baohong.liu@intel.com>
Cc: Vedang Patel <vedang.patel@intel.com>
Cc: kernel-team@android.com
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

  parent reply	other threads:[~2018-05-07 20:42 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-07 20:41 [PATCH RFC v6 0/5] Centralize and unify usage of preempt/irq tracepoints Joel Fernandes
2018-05-07 20:41 ` [PATCH RFC v6 1/5] srcu: Add notrace variants of srcu_read_{lock,unlock} Joel Fernandes
2018-05-07 20:41 ` Joel Fernandes [this message]
2018-05-07 20:41 ` [PATCH RFC v6 3/5] trace/irqsoff: Split reset into separate functions Joel Fernandes
2018-05-07 20:41 ` [PATCH RFC v6 4/5] tracepoint: Make rcuidle tracepoint callers use SRCU Joel Fernandes
2018-05-07 21:05   ` Mathieu Desnoyers
2018-05-07 21:46     ` Joel Fernandes
2018-05-08  0:37       ` Mathieu Desnoyers
2018-05-08 21:10         ` Joel Fernandes
2018-05-07 21:08   ` Paul E. McKenney
2018-05-07 21:17     ` Mathieu Desnoyers
2018-05-07 21:45     ` Joel Fernandes
2018-05-07 21:55       ` Paul E. McKenney
2018-05-07 23:37         ` Joel Fernandes
2018-05-07 20:41 ` [PATCH RFC v6 5/5] tracing: Centralize preemptirq tracepoints and unify their usage Joel Fernandes

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