rculist: avoid __rcu annotations

This avoids warnings from missing __rcu annotations
in the rculist implementation, making it possible to
use the same lists in both RCU and non-RCU cases.

We can add rculist annotations later, together with
lockdep support for rculist, which is missing as well,
but that may involve changing all the users.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index 4ec3b38ce9c584049229b71bbf537770d6fbe263..c10b1050dbe6c617419b0dd89a86f52b96fe3979 100644 (file)
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -9,6 +9,12 @@
 #include <linux/list.h>
 #include <linux/rcupdate.h>
 
+/*
+ * 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.
  *
@@ -20,7 +26,7 @@ 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 +144,7 @@ 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 +199,7 @@ 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 +214,9 @@ 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 +233,9 @@ 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 +265,9 @@ 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 +322,19 @@ 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 +361,7 @@ 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 +389,7 @@ 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 +416,15 @@ 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 +437,11 @@ 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

diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h
index b70ffe53cb9fe77a668f57c2bc584216f90f95b6..2ae13714828bc42568e77684fedfc2cf929c291d 100644 (file)
--- a/include/linux/rculist_nulls.h
+++ b/include/linux/rculist_nulls.h
@@ -37,6 +37,12 @@ static inline void hlist_nulls_del_init_rcu(struct hlist_nulls_node *n)
        }
 }
 
+#define hlist_nulls_first_rcu(head) \
+       (*((struct hlist_nulls_node __rcu __force **)&(head)->first))
+
+#define hlist_nulls_next_rcu(node) \
+       (*((struct hlist_nulls_node __rcu __force **)&(node)->next))
+
 /**
  * hlist_nulls_del_rcu - deletes entry from hash list without re-initialization
  * @n: the element to delete from the hash list.
@@ -88,7 +94,7 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
 
        n->next = first;
        n->pprev = &h->first;
-       rcu_assign_pointer(h->first, n);
+       rcu_assign_pointer(hlist_nulls_first_rcu(h), n);
        if (!is_a_nulls(first))
                first->pprev = &n->next;
 }
@@ -100,11 +106,11 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n,
  * @member:    the name of the hlist_nulls_node within the struct.
  *
  */
-#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member) \
-       for (pos = rcu_dereference_raw((head)->first);                   \
-               (!is_a_nulls(pos)) &&                   \
+#define hlist_nulls_for_each_entry_rcu(tpos, pos, head, member)                        \
+       for (pos = rcu_dereference_raw(hlist_nulls_first_rcu(head));            \
+               (!is_a_nulls(pos)) &&                                           \
                ({ tpos = hlist_nulls_entry(pos, typeof(*tpos), member); 1; }); \
-               pos = rcu_dereference_raw(pos->next))
+               pos = rcu_dereference_raw(hlist_nulls_next_rcu(pos)))
 
 #endif
 #endif

diff --git a/kernel/pid.c b/kernel/pid.c
index d55c6fb8d087a24a2d462886dfe1fc53bf9deced..0f90c2f713f117d8de65baddb3fa561b51ddf240 100644 (file)
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -401,7 +401,7 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type)
        struct task_struct *result = NULL;
        if (pid) {
                struct hlist_node *first;
-               first = rcu_dereference_check(pid->tasks[type].first,
+               first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
                                              rcu_read_lock_held() ||
                                              lockdep_tasklist_lock_is_held());
                if (first)