From: Willy Tarreau <w@1wt.eu>
Date: Mon, 5 Feb 2018 18:43:30 +0000 (+0100)
Subject: BUG/MINOR: fd/threads: properly dereference fdcache as volatile
X-Git-Tag: v1.9-dev1~437
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=abeaff2d543fded7ffc14dd908d673c59d725155;p=thirdparty%2Fhaproxy.git

BUG/MINOR: fd/threads: properly dereference fdcache as volatile

In fd_rm_from_fd_list(), we have loops waiting for another change to
complete, in case we don't have support for a double CAS. But these
ones fail to place a compiler barrier or to dereference the fdcache
as a volatile, resulting in an endless loop on the first collision,
which is visible when run on MIPS32.

No backport needed.
---

diff --git a/src/fd.c b/src/fd.c
index 108235332e..04ac3350a9 100644
--- a/src/fd.c
+++ b/src/fd.c
@@ -281,7 +281,7 @@ lock_self:
 
 #else
 lock_self_next:
-	next = fdtab[fd].cache.next;
+	next = pl_deref_int(&fdtab[fd].cache.next);
 	if (next == -2)
 		goto lock_self_next;
 	if (next <= -3)
@@ -289,7 +289,7 @@ lock_self_next:
 	if (unlikely(!HA_ATOMIC_CAS(&fdtab[fd].cache.next, &next, -2)))
 		goto lock_self_next;
 lock_self_prev:
-	prev = fdtab[fd].cache.prev;
+	prev = pl_deref_int(&fdtab[fd].cache.prev);
 	if (prev == -2)
 		goto lock_self_prev;
 	if (unlikely(!HA_ATOMIC_CAS(&fdtab[fd].cache.prev, &prev, -2)))