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Subject[tip:core/rcu] rcu: Add lockdep-enabled variants of rcu_dereference()
Commit-ID:  c26d34a5858f96a564c45048bf5f09319d2abad1
Gitweb: http://git.kernel.org/tip/c26d34a5858f96a564c45048bf5f09319d2abad1
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Mon, 22 Feb 2010 17:04:46 -0800
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 25 Feb 2010 09:41:00 +0100

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>
---
include/linux/rcupdate.h | 41 ++++++++++++++++++++++++++++++++++-------
include/linux/srcu.h | 8 ++++++++
2 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e3d37ef..839d296 100644
--- 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 */

@@ -325,22 +325,49 @@ 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.
*

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