On 1/15/25 6:24 PM, Olga Kornievskaia wrote:
nfsd stores its network transports in a lwq (which is a lockless list)
llist has no ability to remove a particular entry which nfsd needs
to remove a listener thread.
Note that scripts/get_maintainer.pl says that the maintainer of this
file is:
linux-kernel@xxxxxxxxxxxxxxx
so that address should appear on the cc: list of this series. So
should the list of reviewers for NFSD that appear in MAINTAINERS.
ISTR Neil found the same gap in the llist API. I don't think it's
possible to safely remove an item from the middle of an llist. Much
of the complexity of the current svc thread scheduler is due to this
complication.
I think you will need to mark the listener as dead and find some
way of safely dealing with it later.
Suggested-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Olga Kornievskaia <okorniev@xxxxxxxxxx>
---
include/linux/llist.h | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/include/linux/llist.h b/include/linux/llist.h
index 2c982ff7475a..fe6be21897d9 100644
--- a/include/linux/llist.h
+++ b/include/linux/llist.h
@@ -253,6 +253,42 @@ static inline bool __llist_add(struct llist_node *new, struct llist_head *head)
return __llist_add_batch(new, new, head);
}
+/**
+ * llist_del_entry - remove a particular entry from a lock-less list
+ * @head: head of the list to remove the entry from
+ * @entry: entry to be removed from the list
+ *
+ * Walk the list, find the given entry and remove it from the list.
+ * The caller must ensure that nothing can race in and change the
+ * list while this is running.
+ *
+ * Returns true if the entry was found and removed.
+ */
+static inline bool llist_del_entry(struct llist_head *head, struct llist_node *entry)
+{
+ struct llist_node *pos;
+
+ if (!head->first)
+ return false;
+
+ /* Is it the first entry? */
+ if (head->first == entry) {
+ head->first = entry->next;
+ entry->next = entry;
+ return true;
+ }
+
+ /* Find it in the list */
+ llist_for_each(head->first, pos) {
+ if (pos->next == entry) {
+ pos->next = entry->next;
+ entry->next = entry;
+ return true;
+ }
+ }
+ return false;
+}
+
/**
* llist_del_all - delete all entries from lock-less list
* @head: the head of lock-less list to delete all entries
--
Chuck Lever
