1 files changed, 43 insertions, 19 deletions

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 4ec3b38ce9c5..f31ef61f1c65 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -10,6 +10,21 @@
 #include <linux/rcupdate.h>
 
 /*
+ * Why is there no list_empty_rcu()?  Because list_empty() serves this
+ * purpose.  The list_empty() function fetches the RCU-protected pointer
+ * and compares it to the address of the list head, but neither dereferences
+ * this pointer itself nor provides this pointer to the caller.  Therefore,
+ * it is not necessary to use rcu_dereference(), so that list_empty() can
+ * be used anywhere you would want to use a list_empty_rcu().
+ */
+
+/*
+ * return the ->next pointer of a list_head in an rcu safe
+ * way, we must not access it directly
+ */
+#define list_next_rcu(list)     (*((struct list_head __rcu **)(&(list)->next)))
+
+/*
  * Insert a new entry between two known consecutive entries.
  *
  * This is only for internal list manipulation where we know
@@ -20,7 +35,7 @@ static inline void __list_add_rcu(struct list_head *new,
 {
         new->next = next;
         new->prev = prev;
-        rcu_assign_pointer(prev->next, new);
+        rcu_assign_pointer(list_next_rcu(prev), new);
         next->prev = new;
 }
 
@@ -138,7 +153,7 @@ static inline void list_replace_rcu(struct list_head *old,
 {
         new->next = old->next;
         new->prev = old->prev;
-        rcu_assign_pointer(new->prev->next, new);
+        rcu_assign_pointer(list_next_rcu(new->prev), new);
         new->next->prev = new;
         old->prev = LIST_POISON2;
 }
@@ -193,7 +208,7 @@ static inline void list_splice_init_rcu(struct list_head *list,
          */
 
         last->next = at;
-        rcu_assign_pointer(head->next, first);
+        rcu_assign_pointer(list_next_rcu(head), first);
         first->prev = head;
         at->prev = last;
 }
@@ -208,7 +223,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
  */
 #define list_entry_rcu(ptr, type, member) \
-        container_of(rcu_dereference_raw(ptr), type, member)
+        ({typeof (*ptr) __rcu *__ptr = (typeof (*ptr) __rcu __force *)ptr; \
+         container_of((typeof(ptr))rcu_dereference_raw(__ptr), type, member); \
+        })
 
 /**
  * list_first_entry_rcu - get the first element from a list
@@ -225,9 +242,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
         list_entry_rcu((ptr)->next, type, member)
 
 #define __list_for_each_rcu(pos, head) \
-        for (pos = rcu_dereference_raw((head)->next); \
+        for (pos = rcu_dereference_raw(list_next_rcu(head)); \
                 pos != (head); \
-                pos = rcu_dereference_raw(pos->next))
+                pos = rcu_dereference_raw(list_next_rcu((pos)))
 
 /**
  * list_for_each_entry_rcu      -       iterate over rcu list of given type
@@ -257,9 +274,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_continue_rcu(pos, head) \
-        for ((pos) = rcu_dereference_raw((pos)->next); \
+        for ((pos) = rcu_dereference_raw(list_next_rcu(pos)); \
                 prefetch((pos)->next), (pos) != (head); \
-                (pos) = rcu_dereference_raw((pos)->next))
+                (pos) = rcu_dereference_raw(list_next_rcu(pos)))
 
 /**
  * list_for_each_entry_continue_rcu - continue iteration over list of given type
@@ -314,12 +331,19 @@ static inline void hlist_replace_rcu(struct hlist_node *old,
 
         new->next = next;
         new->pprev = old->pprev;
-        rcu_assign_pointer(*new->pprev, new);
+        rcu_assign_pointer(*(struct hlist_node __rcu **)new->pprev, new);
         if (next)
                 new->next->pprev = &new->next;
         old->pprev = LIST_POISON2;
 }
 
+/*
+ * return the first or the next element in an RCU protected hlist
+ */
+#define hlist_first_rcu(head)   (*((struct hlist_node __rcu **)(&(head)->first)))
+#define hlist_next_rcu(node)    (*((struct hlist_node __rcu **)(&(node)->next)))
+#define hlist_pprev_rcu(node)   (*((struct hlist_node __rcu **)((node)->pprev)))
+
 /**
  * hlist_add_head_rcu
  * @n: the element to add to the hash list.
@@ -346,7 +370,7 @@ static inline void hlist_add_head_rcu(struct hlist_node *n,
 
         n->next = first;
         n->pprev = &h->first;
-        rcu_assign_pointer(h->first, n);
+        rcu_assign_pointer(hlist_first_rcu(h), n);
         if (first)
                 first->pprev = &n->next;
 }
@@ -374,7 +398,7 @@ static inline void hlist_add_before_rcu(struct hlist_node *n,
 {
         n->pprev = next->pprev;
         n->next = next;
-        rcu_assign_pointer(*(n->pprev), n);
+        rcu_assign_pointer(hlist_pprev_rcu(n), n);
         next->pprev = &n->next;
 }
 
@@ -401,15 +425,15 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
 {
         n->next = prev->next;
         n->pprev = &prev->next;
-        rcu_assign_pointer(prev->next, n);
+        rcu_assign_pointer(hlist_next_rcu(prev), n);
         if (n->next)
                 n->next->pprev = &n->next;
 }
 
-#define __hlist_for_each_rcu(pos, head)                 \
-        for (pos = rcu_dereference((head)->first);      \
-             pos && ({ prefetch(pos->next); 1; });      \
-             pos = rcu_dereference(pos->next))
+#define __hlist_for_each_rcu(pos, head)                         \
+        for (pos = rcu_dereference(hlist_first_rcu(head));      \
+             pos && ({ prefetch(pos->next); 1; });              \
+             pos = rcu_dereference(hlist_next_rcu(pos)))
 
 /**
  * hlist_for_each_entry_rcu - iterate over rcu list of given type
@@ -422,11 +446,11 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
  * the _rcu list-mutation primitives such as hlist_add_head_rcu()
  * as long as the traversal is guarded by rcu_read_lock().
  */
-#define hlist_for_each_entry_rcu(tpos, pos, head, member)                \
-        for (pos = rcu_dereference_raw((head)->first);                   \
+#define hlist_for_each_entry_rcu(tpos, pos, head, member)               \
+        for (pos = rcu_dereference_raw(hlist_first_rcu(head));          \
                 pos && ({ prefetch(pos->next); 1; }) &&                  \
                 ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
-                pos = rcu_dereference_raw(pos->next))
+                pos = rcu_dereference_raw(hlist_next_rcu(pos)))
 
 /**
  * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type