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authorBoqun Feng <boqun.feng@gmail.com>2015-12-29 12:18:47 +0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2016-02-23 19:59:54 -0800
commit67c583a7de3433a971983490b37ad2bff3c55463 (patch)
treeb6d5123664992047b393594cff856de006fb86b4 /kernel/rcu/tree.h
parentad315455d396a1cbcb2f9fdd687b7e1b26b789e7 (diff)
downloadlinux-sh-67c583a7de3433a971983490b37ad2bff3c55463.tar.gz
RCU: Privatize rcu_node::lock
In patch: "rcu: Add transitivity to remaining rcu_node ->lock acquisitions" All locking operations on rcu_node::lock are replaced with the wrappers because of the need of transitivity, which indicates we should never write code using LOCK primitives alone(i.e. without a proper barrier following) on rcu_node::lock outside those wrappers. We could detect this kind of misuses on rcu_node::lock in the future by adding __private modifier on rcu_node::lock. To privatize rcu_node::lock, unlock wrappers are also needed. Replacing spinlock unlocks with these wrappers not only privatizes rcu_node::lock but also makes it easier to figure out critical sections of rcu_node. This patch adds __private modifier to rcu_node::lock and makes every access to it wrapped by ACCESS_PRIVATE(). Besides, unlock wrappers are added and raw_spin_unlock(&rnp->lock) and its friends are replaced with those wrappers. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.h')
-rw-r--r--kernel/rcu/tree.h42
1 files changed, 31 insertions, 11 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 83360b4f4352..4886d6a03353 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -149,8 +149,9 @@ struct rcu_dynticks {
* Definition for node within the RCU grace-period-detection hierarchy.
*/
struct rcu_node {
- raw_spinlock_t lock; /* Root rcu_node's lock protects some */
- /* rcu_state fields as well as following. */
+ raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
+ /* some rcu_state fields as well as */
+ /* following. */
unsigned long gpnum; /* Current grace period for this node. */
/* This will either be equal to or one */
/* behind the root rcu_node's gpnum. */
@@ -680,7 +681,7 @@ static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
#endif /* #else #ifdef CONFIG_PPC */
/*
- * Wrappers for the rcu_node::lock acquire.
+ * Wrappers for the rcu_node::lock acquire and release.
*
* Because the rcu_nodes form a tree, the tree traversal locking will observe
* different lock values, this in turn means that an UNLOCK of one level
@@ -689,29 +690,48 @@ static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
*
* In order to restore full ordering between tree levels, augment the regular
* lock acquire functions with smp_mb__after_unlock_lock().
+ *
+ * As ->lock of struct rcu_node is a __private field, therefore one should use
+ * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
*/
static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp)
{
- raw_spin_lock(&rnp->lock);
+ raw_spin_lock(&ACCESS_PRIVATE(rnp, lock));
smp_mb__after_unlock_lock();
}
+static inline void raw_spin_unlock_rcu_node(struct rcu_node *rnp)
+{
+ raw_spin_unlock(&ACCESS_PRIVATE(rnp, lock));
+}
+
static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp)
{
- raw_spin_lock_irq(&rnp->lock);
+ raw_spin_lock_irq(&ACCESS_PRIVATE(rnp, lock));
smp_mb__after_unlock_lock();
}
-#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \
-do { \
- typecheck(unsigned long, flags); \
- raw_spin_lock_irqsave(&(rnp)->lock, flags); \
- smp_mb__after_unlock_lock(); \
+static inline void raw_spin_unlock_irq_rcu_node(struct rcu_node *rnp)
+{
+ raw_spin_unlock_irq(&ACCESS_PRIVATE(rnp, lock));
+}
+
+#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \
+do { \
+ typecheck(unsigned long, flags); \
+ raw_spin_lock_irqsave(&ACCESS_PRIVATE(rnp, lock), flags); \
+ smp_mb__after_unlock_lock(); \
+} while (0)
+
+#define raw_spin_unlock_irqrestore_rcu_node(rnp, flags) \
+do { \
+ typecheck(unsigned long, flags); \
+ raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(rnp, lock), flags); \
} while (0)
static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp)
{
- bool locked = raw_spin_trylock(&rnp->lock);
+ bool locked = raw_spin_trylock(&ACCESS_PRIVATE(rnp, lock));
if (locked)
smp_mb__after_unlock_lock();