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[v8,3/8] srcu: Add notrace variant of srcu_dereference

Message ID 20180530000500.257225-4-joel@joelfernandes.org (mailing list archive)
State New
Headers show

Commit Message

Joel Fernandes May 30, 2018, 12:04 a.m. UTC
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(+)
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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.