Fix use of process_info(Pid, monitored_by)

This can now return references that are from NIFs monitoring the
process. This is important for the new file IO NIFs that monitor the
controlling process. For now we'll just take the easy way out by
filtering the references from our returned monitor lists.

Fixes #1396

3 files changed, 12 insertions, 8 deletions

diff --git a/src/couch/src/couch_bt_engine.erl b/src/couch/src/couch_bt_engine.erl
index 6d858ed49..f856bde8f 100644
--- a/src/couch/src/couch_bt_engine.erl
+++ b/src/couch/src/couch_bt_engine.erl
@@ -196,7 +196,7 @@ decref(St) ->
 monitored_by(St) ->
     case erlang:process_info(St#st.fd, monitored_by) of
         {monitored_by, Pids} ->
-            Pids;
+            lists:filter(fun is_pid/1, Pids);
         _ ->
             []
     end.
diff --git a/src/couch/src/couch_file.erl b/src/couch/src/couch_file.erl
index 6aa8d0b89..0c6070dad 100644
--- a/src/couch/src/couch_file.erl
+++ b/src/couch/src/couch_file.erl
@@ -695,19 +695,22 @@ split_iolist([Sublist| Rest], SplitAt, BeginAcc) when is_list(Sublist) ->
 split_iolist([Byte | Rest], SplitAt, BeginAcc) when is_integer(Byte) ->
     split_iolist(Rest, SplitAt - 1, [Byte | BeginAcc]).
 
+monitored_by_pids() ->
+    {monitored_by, PidsAndRefs} = process_info(self(), monitored_by),
+    lists:filter(fun is_pid/1, PidsAndRefs).
 
 % System dbs aren't monitored by couch_stats_process_tracker
 is_idle(#file{is_sys=true}) ->
-    case process_info(self(), monitored_by) of
-        {monitored_by, []} -> true;
+    case monitored_by_pids() of
+        [] -> true;
         _ -> false
     end;
 is_idle(#file{is_sys=false}) ->
     Tracker = whereis(couch_stats_process_tracker),
-    case process_info(self(), monitored_by) of
-        {monitored_by, []} -> true;
-        {monitored_by, [Tracker]} -> true;
-        {monitored_by, [_]} -> exit(tracker_monitoring_failed);
+    case monitored_by_pids() of
+        [] -> true;
+        [Tracker] -> true;
+        [_] -> exit(tracker_monitoring_failed);
         _ -> false
     end.
 
diff --git a/src/couch/test/couchdb_views_tests.erl b/src/couch/test/couchdb_views_tests.erl
index 1b1a8e56b..60bb5c975 100644
--- a/src/couch/test/couchdb_views_tests.erl
+++ b/src/couch/test/couchdb_views_tests.erl
@@ -523,7 +523,8 @@ view_cleanup(DbName) ->
 count_users(DbName) ->
     {ok, Db} = couch_db:open_int(DbName, [?ADMIN_CTX]),
     DbPid = couch_db:get_pid(Db),
-    {monitored_by, Monitors} = process_info(DbPid, monitored_by),
+    {monitored_by, Monitors0} = process_info(DbPid, monitored_by),
+    Monitors = lists:filter(fun is_pid/1, Monitors0),
     CouchFiles = [P || P <- Monitors, couch_file:process_info(P) =/= undefined],
     ok = couch_db:close(Db),
     length(lists:usort(Monitors) -- [self() | CouchFiles]).