@@ -750,3 +750,74 @@ struct hlist_node *seq_hlist_next(void *
return node->next;
}
EXPORT_SYMBOL(seq_hlist_next);
+
+/**
+ * seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
+ * @head: the head of the hlist
+ * @pos: the start position of the sequence
+ *
+ * Called at seq_file->op->start().
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
+ loff_t pos)
+{
+ struct hlist_node *node;
+
+ __hlist_for_each_rcu(node, head)
+ if (pos-- == 0)
+ return node;
+ return NULL;
+}
+EXPORT_SYMBOL(seq_hlist_start_rcu);
+
+/**
+ * seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
+ * @head: the head of the hlist
+ * @pos: the start position of the sequence
+ *
+ * Called at seq_file->op->start(). Call this function if you want to
+ * print a header at the top of the output.
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
+ loff_t pos)
+{
+ if (!pos)
+ return SEQ_START_TOKEN;
+
+ return seq_hlist_start_rcu(head, pos - 1);
+}
+EXPORT_SYMBOL(seq_hlist_start_head_rcu);
+
+/**
+ * seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
+ * @v: the current iterator
+ * @head: the head of the hlist
+ * @pos: the current posision
+ *
+ * Called at seq_file->op->next().
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as hlist_add_head_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+struct hlist_node *seq_hlist_next_rcu(void *v,
+ struct hlist_head *head,
+ loff_t *ppos)
+{
+ struct hlist_node *node = v;
+
+ ++*ppos;
+ if (v == SEQ_START_TOKEN)
+ return rcu_dereference(head->first);
+ else
+ return rcu_dereference(node->next);
+}
+EXPORT_SYMBOL(seq_hlist_next_rcu);
@@ -140,10 +140,17 @@ extern struct list_head *seq_list_next(v
*/
extern struct hlist_node *seq_hlist_start(struct hlist_head *head,
- loff_t pos);
+ loff_t pos);
extern struct hlist_node *seq_hlist_start_head(struct hlist_head *head,
- loff_t pos);
+ loff_t pos);
extern struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
- loff_t *ppos);
+ loff_t *ppos);
+extern struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
+ loff_t pos);
+extern struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
+ loff_t pos);
+extern struct hlist_node *seq_hlist_next_rcu(void *v,
+ struct hlist_head *head,
+ loff_t *ppos);
#endif
@@ -406,6 +406,11 @@ static inline void hlist_add_after_rcu(s
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))
+
/**
* hlist_for_each_entry_rcu - iterate over rcu list of given type
* @tpos: the type * to use as a loop cursor.
Many usages of seq_file use RCU protected lists, so non RCU iterators will not work safely. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> --- Add comment (same as other RCU functions) fs/seq_file.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/rculist.h | 5 ++++ include/linux/seq_file.h | 12 +++++++--- 3 files changed, 70 insertions(+), 3 deletions(-)