3 files changed, 23 insertions, 1 deletions
diff --git a/src/or/config.c b/src/or/config.c
index 54f3930fc5..208680060f 100644
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -1547,6 +1547,7 @@ options_act_reversible(const or_options_t *old_options, char **msg)
       tor_malloc_zero(sizeof(log_severity_list_t));
     close_temp_logs();
     add_callback_log(severity, control_event_logmsg);
+    logs_set_pending_callback_callback(control_event_logmsg_pending);
     control_adjust_event_log_severity();
     tor_free(severity);
     tor_log_update_sigsafe_err_fds();
diff --git a/src/or/control.c b/src/or/control.c
index dda8872182..7ad9460cc8 100644
--- a/src/or/control.c
+++ b/src/or/control.c
@@ -803,6 +803,9 @@ queued_event_free_(queued_event_t *ev)
 static void
 queued_events_flush_all(int force)
 {
+  /* Make sure that we get all the pending log events, if there are any. */
+  flush_pending_log_callbacks();
+
   if (PREDICT_UNLIKELY(queued_control_events == NULL)) {
     return;
   }
@@ -6186,7 +6189,7 @@ control_event_logmsg(int severity, uint32_t domain, const char *msg)
   int event;
 
   /* Don't even think of trying to add stuff to a buffer from a cpuworker
-   * thread. */
+   * thread. (See #25987 for plan to fix.) */
   if (! in_main_thread())
     return;
 
@@ -6232,6 +6235,23 @@ control_event_logmsg(int severity, uint32_t domain, const char *msg)
   }
 }
 
+/**
+ * Logging callback: called when there is a queued pending log callback.
+ */
+void
+control_event_logmsg_pending(void)
+{
+  if (! in_main_thread()) {
+    /* We can't handle this case yet, since we're using a
+     * mainloop_event_t to invoke queued_events_flush_all.  We ought to
+     * use a different mechanism instead: see #25987.
+     **/
+    return;
+  }
+  tor_assert(flush_queued_events_event);
+  mainloop_event_activate(flush_queued_events_event);
+}
+
 /** Called whenever we receive new router descriptors: tell any
  * interested control connections.  <b>routers</b> is a list of
  * routerinfo_t's.
diff --git a/src/or/control.h b/src/or/control.h
index 2f312a6638..7f8a0bdb5f 100644
--- a/src/or/control.h
+++ b/src/or/control.h
@@ -60,6 +60,7 @@ int control_event_conn_bandwidth(connection_t *conn);
 int control_event_conn_bandwidth_used(void);
 int control_event_circuit_cell_stats(void);
 void control_event_logmsg(int severity, uint32_t domain, const char *msg);
+void control_event_logmsg_pending(void);
 int control_event_descriptors_changed(smartlist_t *routers);
 int control_event_address_mapped(const char *from, const char *to,
                                  time_t expires, const char *error,