rcu: Add lockdep-enabled variants of rcu_dereference()

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, and make rcu_dereference_check() use
rcu_dereference_raw().

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1266887105-1528-2-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e3d37efe270329c3fa6222a9ac7ec995708cd53a..839d296a7ac0268071d32409745c2ea734c9b78c 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -184,12 +184,12 @@ 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_PROVE_RCU */
 
-#define rcu_dereference_check(p, c)    rcu_dereference(p)
+#define rcu_dereference_check(p, c)    rcu_dereference_raw(p)
 
 #endif /* #else #ifdef CONFIG_PROVE_RCU */
 
@@ -325,21 +325,48 @@ 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

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index adbe1670b3660078a0d0892a84f3fc6de8510ce9..3084f80909cd91bf684dea1c1dcae3fb4f2d2292 100644 (file)
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -105,6 +105,14 @@ 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.