BUG/MAJOR: server: fix deadlock when changing maxconn via agent-check
The server_parse_maxconn_change_request locks the server lock. However,
this function can be called via agent-checks or lua code which already
lock it. This bug has been introduced by the following commit :
commit 79a88ba3d09f7e2b73ae27cb5d24cc087a548fa6
BUG/MAJOR: server: prevent deadlock when using 'set maxconn server'
This commit tried to fix another deadlock with can occur because
previoulsy server_parse_maxconn_change_request requires the server lock
to be held. However, it may call internally process_srv_queue which also
locks the server lock. The locking policy has thus been updated. The fix
is functional for the CLI 'set maxconn' but fails to address the
agent-check / lua counterparts.
This new issue is fixed in two steps :
- changes from the above commit have been reverted. This means that
server_parse_maxconn_change_request must again be called with the
server lock.
- to counter the deadlock fixed by the above commit, process_srv_queue
now takes an argument to render the server locking optional if the
caller already held it. This is only used by
server_parse_maxconn_change_request.
The above commit was subject to backport up to 1.8. Thus this commit
must be backported in every release where it is already present.
(cherry picked from commit 0274286dd3768c0d5e58588a1cb7e7e710fbc9d4)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit caaafd055edcbceb3d57ed9672b90900ec52a203)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/tcpcheck.c b/src/tcpcheck.c
index f889dff..896d4ee 100644
--- a/src/tcpcheck.c
+++ b/src/tcpcheck.c
@@ -913,6 +913,9 @@
cs += strlen("maxconn:");
+ /* This is safe to call server_parse_maxconn_change_request
+ * because the server lock is held during the check.
+ */
msg = server_parse_maxconn_change_request(check->server, cs);
if (!wrn || !*wrn)
wrn = msg;