commit f4be23cefd779894ca85680d85b1d66cd22d42b6
Author: Willy Tarreau <w@1wt.eu>
Date:   Thu Feb 28 15:05:53 2019 +0100

    MINOR: list: make the delete and pop operations idempotent
    
    These operations previously used to return a "locked" element, which is
    a constraint when multiple threads try to delete the same element, because
    the second one will block indefinitely. Instead, let's make sure that both
    LIST_DEL_LOCKED() and LIST_POP_LOCKED() always reinitialize the element
    after deleting it. This ensures that the second thread will immediately
    unblock and succeed with the removal. It also secures the pop vs delete
    competition that may happen when trying to remove an element that's about
    to be dequeued.
    
    (cherry picked from commit 4c747e86cda5d7eab46390779447f216ce9aa5de)
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    (cherry picked from commit 731853a3e19b2ce314c1626360dc5b1dcba5baa1)
    Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/include/common/mini-clist.h b/include/common/mini-clist.h
index 92a995c9..d4861ccc 100644
--- a/include/common/mini-clist.h
+++ b/include/common/mini-clist.h
@@ -261,6 +261,9 @@ struct cond_wordlist {
 			n->p = p;                                          \
 			p->n = n;                                          \
 			__ha_barrier_store();                              \
+			(el)->p = (el);                                    \
+			(el)->n = (el);	                                   \
+			__ha_barrier_store();                              \
 			break;                                             \
 		}                                                          \
 	} while (0)
@@ -308,6 +311,9 @@ struct cond_wordlist {
 			 (lh)->n = n2;                                     \
 			 (n2)->p = (lh);                                   \
 			 __ha_barrier_store();                             \
+			 (n)->p = (n);                                     \
+			 (n)->n = (n);	                                   \
+			 __ha_barrier_store();                             \
 			 _ret = LIST_ELEM(n, pt, el);                      \
 			 break;                                            \
 		 }                                                         \