thread safety enhancements

docs/ares_init_options.3

@@ -216,8 +216,9 @@ The value of
 .I sock_state_cb_data
 will be passed as the
 .I data
-argument.  Since this may be called cross-thread, a channel lock is NOT held
-when this callback is called.
+argument.  The channel lock is held during this callback, if calling
+cross-thread care must be taken to ensure no other c-ares functions are
+called from this callback.
 .TP 18
 .B ARES_OPT_SORTLIST
 .B struct apattern *\fIsortlist\fP;

src/lib/ares_private.h

@@ -563,9 +563,7 @@ ares_status_t ares__dns_name_write(ares__buf_t *buf, ares__llist_t **list,
 #define SOCK_STATE_CALLBACK(c, s, r, w)                           \
   do {                                                            \
     if ((c)->sock_state_cb) {                                     \
-      ares__channel_unlock((c));                                  \
       (c)->sock_state_cb((c)->sock_state_cb_data, (s), (r), (w)); \
-      ares__channel_lock((c));                                    \
     }                                                             \
   } while (0)