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Subject[PATCH tip/core/rcu 2/8] rcu: add lockdep-enabled variants of rcu_dereference()
Date
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Make rcu_dereference() check for being in an RCU read-side critical
section, and create rcu_dereference_bh(), rcu_dereference_sched(), and
srcu_dereference() to check for the other flavors of RCU. Also create
rcu_dereference_raw() to avoid checking.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/linux/rcupdate.h | 45 ++++++++++++++++++++++++++++++++++-----------
include/linux/srcu.h | 8 ++++++++
2 files changed, 42 insertions(+), 11 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index aa6c738..a52af93 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -156,7 +156,7 @@ static inline int rcu_read_lock_sched_held(void)
({ \
if (debug_locks) \
WARN_ON_ONCE(!(c)); \
- rcu_dereference(p); \
+ rcu_dereference_raw(p); \
})

#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@@ -183,11 +183,7 @@ static inline int rcu_read_lock_sched_held(void)
return preempt_count() != 0;
}

-#define rcu_dereference_check(p, c) \
- ({ \
- (void)(c); \
- rcu_dereference(p); \
- })
+#define rcu_dereference_check(p, c) rcu_dereference_raw(p)

#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

@@ -323,22 +319,49 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)


/**
- * rcu_dereference - fetch an RCU-protected pointer in an
- * RCU read-side critical section. This pointer may later
- * be safely dereferenced.
+ * rcu_dereference_raw - fetch an RCU-protected pointer
+ *
+ * The caller must be within some flavor of RCU read-side critical
+ * section, or must be otherwise preventing the pointer from changing,
+ * for example, by holding an appropriate lock. This pointer may later
+ * be safely dereferenced. It is the caller's responsibility to have
+ * done the right thing, as this primitive does no checking of any kind.
*
* Inserts memory barriers on architectures that require them
* (currently only the Alpha), and, more importantly, documents
* exactly which pointers are protected by RCU.
*/
-
-#define rcu_dereference(p) ({ \
+#define rcu_dereference_raw(p) ({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
smp_read_barrier_depends(); \
(_________p1); \
})

/**
+ * rcu_dereference - fetch an RCU-protected pointer, checking for RCU
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference(p) \
+ rcu_dereference_check(p, rcu_read_lock_held())
+
+/**
+ * rcu_dereference_bh - fetch an RCU-protected pointer, checking for RCU-bh
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_bh(p) \
+ rcu_dereference_check(p, rcu_read_lock_bh_held())
+
+/**
+ * rcu_dereference_sched - fetch RCU-protected pointer, checking for RCU-sched
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_sched(p) \
+ rcu_dereference_check(p, rcu_read_lock_sched_held())
+
+/**
* rcu_assign_pointer - assign (publicize) a pointer to a newly
* initialized structure that will be dereferenced by RCU read-side
* critical sections. Returns the value assigned.
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index adbe167..3084f80 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -106,6 +106,14 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

/**
+ * srcu_dereference - fetch SRCU-protected pointer with checking
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define srcu_dereference(p, sp) \
+ rcu_dereference_check(p, srcu_read_lock_held(sp))
+
+/**
* srcu_read_lock - register a new reader for an SRCU-protected structure.
* @sp: srcu_struct in which to register the new reader.
*
--
1.5.2.5


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