mon/MonClient: set configs via finisher

The config observers may want to take locks that are ordered relative
to monc_lock.

We could simply drop monc_lock for this call, but that would implicitly
rely on a single-threaded dispatch to avoid having two incoming MConfig
messages get reordered.  Explicitly putting it on a finisher is safer.
Note that we adjust the get_monmap_and_config() to start, drain, and stop
the finisher to ensure we have incoming config processed and applied
before returning.

Fixes: http://tracker.ceph.com/issues/24118
Signed-off-by: Sage Weil <sage@redhat.com>

diff --git a/src/mon/MonClient.cc b/src/mon/MonClient.cc
index 5f31182a7614b4cf957de202a0c76b49c1f22cfa..1ad9e50647b166ee3bfad4fb9949823b4d173f72 100644 (file)
--- a/src/mon/MonClient.cc
+++ b/src/mon/MonClient.cc
@@ -374,8 +374,10 @@ void MonClient::handle_monmap(MMonMap *m)
 void MonClient::handle_config(MConfig *m)
 {
   ldout(cct,10) << __func__ << " " << *m << dendl;
-  cct->_conf->set_mon_vals(cct, m->config, config_cb);
-  m->put();
+  finisher.queue(new FunctionContext([this, m](int r) {
+       cct->_conf->set_mon_vals(cct, m->config, config_cb);
+       m->put();
+      }));
   got_config = true;
   map_cond.Signal();
 }