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- commit cee000f97c9300dbbae50118838c6d3e8d5eb9cf
- Author: Willy Tarreau <w@1wt.eu>
- Date: Thu Feb 28 11:14:22 2019 +0100
-
- 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.
-
- (cherry picked from commit 690d2ad4d207da5c8821b84ab467090bd515eedf)
- Signed-off-by: Willy Tarreau <w@1wt.eu>
- (cherry picked from commit c2aa5cb8b8ff3af27f1a962541e53f792745bc4a)
- Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
-
- diff --git a/include/common/mini-clist.h b/include/common/mini-clist.h
- index 51c61051..92a995c9 100644
- --- a/include/common/mini-clist.h
- +++ b/include/common/mini-clist.h
- @@ -189,6 +189,7 @@ struct cond_wordlist {
- } \
- (el)->n = n; \
- (el)->p = p; \
- + __ha_barrier_store(); \
- n->p = (el); \
- __ha_barrier_store(); \
- p->n = (el); \
- @@ -214,6 +215,7 @@ struct cond_wordlist {
- } \
- (el)->n = n; \
- (el)->p = p; \
- + __ha_barrier_store(); \
- n->p = (el); \
- __ha_barrier_store(); \
- p->n = (el); \
- @@ -276,6 +278,7 @@ struct cond_wordlist {
- continue; \
- if (n == (lh)) { \
- (lh)->n = lh; \
- + __ha_barrier_store(); \
- _ret = NULL; \
- break; \
- } \
- @@ -288,6 +291,7 @@ struct cond_wordlist {
- 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 @@ struct cond_wordlist {
- if (p2 == LLIST_BUSY) { \
- n->n = n2; \
- n->p = p; \
- + __ha_barrier_store(); \
- (lh)->n = n; \
- __ha_barrier_store(); \
- continue; \
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