From: Willy Tarreau <w@1wt.eu>
Date: Sun, 7 Dec 2008 19:00:15 +0000 (+0100)
Subject: [MINOR] add a new back-reference type : struct bref
X-Git-Tag: v1.3.16-rc1~112
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bc04ce7cd97410e13de63051190e425c7ee2cab6;p=thirdparty%2Fhaproxy.git

[MINOR] add a new back-reference type : struct bref

This type will be used to maintain back-references to items which
are subject to move between accesses. Typical usage includes session
removal during a listing.
---

diff --git a/include/common/mini-clist.h b/include/common/mini-clist.h
index fca2d76270..7d16b5e46b 100644
--- a/include/common/mini-clist.h
+++ b/include/common/mini-clist.h
@@ -19,6 +19,20 @@ struct list {
     struct list *p;	/* prev */
 };
 
+/* a back-ref is a pointer to a target list entry. It is used to detect when an
+ * element being deleted is currently being tracked by another user. The best
+ * example is a user dumping the session table. The table does not fit in the
+ * output buffer so we have to set a mark on a session and go on later. But if
+ * that marked session gets deleted, we don't want the user's pointer to go in
+ * the wild. So we can simply link this user's request to the list of this
+ * session's users, and put a pointer to the list element in ref, that will be
+ * used as the mark for next iteration.
+ */
+struct bref {
+	struct list users;
+	struct list *ref; /* pointer to the target's list entry */
+};
+
 /* First undefine some macros which happen to also be defined on OpenBSD,
  * in sys/queue.h, used by sys/event.h
  */