BUG/MEDIUM: list: add missing store barriers when updating elements and head
Commit a8434ec14 ("MINOR: lists: Implement locked variations.")
introduced locked lists which use the elements pointers as locks
for concurrent operations. Under heavy stress the lists occasionally
fail. The cause is a missing barrier at some points when updating
the list element and the head : nothing prevents the compiler (or
CPU) from updating the list head first before updating the element,
making another thread jump to a wrong location. This patch simply
adds the missing barriers before these two opeations.
This will have to be backported if the commit above is backported.
diff --git a/include/common/mini-clist.h b/include/common/mini-clist.h
index aefff82..d8fcb15 100644
--- a/include/common/mini-clist.h
+++ b/include/common/mini-clist.h
@@ -189,6 +189,7 @@
} \
(el)->n = n; \
(el)->p = p; \
+ __ha_barrier_store(); \
n->p = (el); \
__ha_barrier_store(); \
p->n = (el); \
@@ -214,6 +215,7 @@
} \
(el)->n = n; \
(el)->p = p; \
+ __ha_barrier_store(); \
n->p = (el); \
__ha_barrier_store(); \
p->n = (el); \
@@ -276,6 +278,7 @@
continue; \
if (n == (lh)) { \
(lh)->n = lh; \
+ __ha_barrier_store(); \
_ret = NULL; \
break; \
} \
@@ -288,6 +291,7 @@
n2 = HA_ATOMIC_XCHG(&n->n, LLIST_BUSY); \
if (n2 == LLIST_BUSY) { \
n->p = p; \
+ __ha_barrier_store(); \
(lh)->n = n; \
__ha_barrier_store(); \
continue; \
@@ -296,6 +300,7 @@
if (p2 == LLIST_BUSY) { \
n->n = n2; \
n->p = p; \
+ __ha_barrier_store(); \
(lh)->n = n; \
__ha_barrier_store(); \
continue; \