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-rw-r--r--include/linux/rcupdate.h28
1 files changed, 27 insertions, 1 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index fe17d7d750c..cc24a01df94 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -41,6 +41,7 @@
#include <linux/percpu.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
+#include <linux/lockdep.h>
/**
* struct rcu_head - callback structure for use with RCU
@@ -133,6 +134,15 @@ static inline void rcu_bh_qsctr_inc(int cpu)
extern int rcu_pending(int cpu);
extern int rcu_needs_cpu(int cpu);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern struct lockdep_map rcu_lock_map;
+# define rcu_read_acquire() lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
+# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
+#else
+# define rcu_read_acquire() do { } while (0)
+# define rcu_read_release() do { } while (0)
+#endif
+
/**
* rcu_read_lock - mark the beginning of an RCU read-side critical section.
*
@@ -166,6 +176,7 @@ extern int rcu_needs_cpu(int cpu);
do { \
preempt_disable(); \
__acquire(RCU); \
+ rcu_read_acquire(); \
} while(0)
/**
@@ -175,6 +186,7 @@ extern int rcu_needs_cpu(int cpu);
*/
#define rcu_read_unlock() \
do { \
+ rcu_read_release(); \
__release(RCU); \
preempt_enable(); \
} while(0)
@@ -204,6 +216,7 @@ extern int rcu_needs_cpu(int cpu);
do { \
local_bh_disable(); \
__acquire(RCU_BH); \
+ rcu_read_acquire(); \
} while(0)
/*
@@ -213,10 +226,23 @@ extern int rcu_needs_cpu(int cpu);
*/
#define rcu_read_unlock_bh() \
do { \
+ rcu_read_release(); \
__release(RCU_BH); \
local_bh_enable(); \
} while(0)
+/*
+ * Prevent the compiler from merging or refetching accesses. The compiler
+ * is also forbidden from reordering successive instances of ACCESS_ONCE(),
+ * but only when the compiler is aware of some particular ordering. One way
+ * to make the compiler aware of ordering is to put the two invocations of
+ * ACCESS_ONCE() in different C statements.
+ *
+ * This macro does absolutely -nothing- to prevent the CPU from reordering,
+ * merging, or refetching absolutely anything at any time.
+ */
+#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
+
/**
* rcu_dereference - fetch an RCU-protected pointer in an
* RCU read-side critical section. This pointer may later
@@ -228,7 +254,7 @@ extern int rcu_needs_cpu(int cpu);
*/
#define rcu_dereference(p) ({ \
- typeof(p) _________p1 = p; \
+ typeof(p) _________p1 = ACCESS_ONCE(p); \
smp_read_barrier_depends(); \
(_________p1); \
})