Merge branch 'lh/demonitor-flush/OTP-11039' into maint

* lh/demonitor-flush/OTP-11039:
  Use erlang:demonitor(Ref, [flush]) where applicable

18 files changed, 48 insertions, 166 deletions

diff --git a/lib/compiler/test/receive_SUITE_data/ref_opt/yes_5.erl b/lib/compiler/test/receive_SUITE_data/ref_opt/yes_5.erl
index 3f02fba6a6..5070e3e546 100644
--- a/lib/compiler/test/receive_SUITE_data/ref_opt/yes_5.erl
+++ b/lib/compiler/test/receive_SUITE_data/ref_opt/yes_5.erl
@@ -24,11 +24,7 @@ do_call(Process, Label, Request, Timeout) ->
 		{'DOWN', Mref, _, _, Reason} ->
 		    exit(Reason)
 	    after Timeout ->
-		    erlang:demonitor(Mref),
-		    receive
-			{'DOWN', Mref, _, _, _} -> true
-		    after 0 -> true
-		    end,
+		    erlang:demonitor(Mref, [flush]),
 		    exit(timeout)
 	    end
     catch
diff --git a/lib/debugger/src/dbg_debugged.erl b/lib/debugger/src/dbg_debugged.erl
index c21ad486e8..d8285d7288 100644
--- a/lib/debugger/src/dbg_debugged.erl
+++ b/lib/debugger/src/dbg_debugged.erl
@@ -19,8 +19,6 @@
 -module(dbg_debugged).
 
 %% External exports
-%% Avoid warning for local function demonitor/1 clashing with autoimported BIF.
--compile({no_auto_import,[demonitor/1]}).
 -export([eval/3]).
 
 %%====================================================================
@@ -47,7 +45,7 @@ msg_loop(Meta, Mref, SaveStacktrace) ->
 
 	%% Evaluated function has returned a value
 	{sys, Meta, {ready, Val}} ->
-	    demonitor(Mref),
+	    erlang:demonitor(Mref, [flush]),
 
 	    %% Restore original stacktrace and return the value
 	    try erlang:raise(throw, stack, SaveStacktrace)
@@ -63,7 +61,7 @@ msg_loop(Meta, Mref, SaveStacktrace) ->
 
 	%% Evaluated function raised an (uncaught) exception
 	{sys, Meta, {exception,{Class,Reason,Stacktrace}}} ->
-	    demonitor(Mref),
+	    erlang:demonitor(Mref, [flush]),
 
 	    %% ...raise the same exception
 	    erlang:error(erlang:raise(Class, Reason, Stacktrace), 
@@ -107,14 +105,6 @@ reply({eval,Expr,Bs}) ->
     %% Bindings is an orddict (sort them)
     erl_eval:expr(Expr, lists:sort(Bs)). % {value, Value, Bs2}
 
-%% Demonitor and delete message from inbox
-%%
-demonitor(Mref) ->
-    erlang:demonitor(Mref),
-    receive {'DOWN',Mref,_,_,_} -> ok
-    after 0 -> ok
-    end.
-
 %% Fix stacktrace - keep all above call to this module.
 %%
 stacktrace_f([]) -> [];
diff --git a/lib/et/src/et_collector.erl b/lib/et/src/et_collector.erl
index a63d15fb4c..ce8cf6d4e0 100644
--- a/lib/et/src/et_collector.erl
+++ b/lib/et/src/et_collector.erl
@@ -654,13 +654,8 @@ start_trace_client(CollectorPid, Type, FileName) when Type =:= file ->
     Ref = erlang:monitor(process, Pid),
     receive
         WaitFor -> 
-	    erlang:demonitor(Ref),
-	    receive 
-		{'DOWN', Ref, _, _, _} ->
-		    file_loaded
-	    after 0 ->
-		    file_loaded
-	    end;
+	    erlang:demonitor(Ref, [flush]),
+	    file_loaded;
         {'DOWN', Ref, _, _, Reason} ->
             exit(Reason)
     end;
diff --git a/lib/kernel/src/application_master.erl b/lib/kernel/src/application_master.erl
index 679fefaed9..34a3efcaf2 100644
--- a/lib/kernel/src/application_master.erl
+++ b/lib/kernel/src/application_master.erl
@@ -76,13 +76,8 @@ call(AppMaster, Req) ->
 	{'DOWN', Ref, process, _, _Info} ->
 	    ok;
 	{Tag, Res} ->
-	    erlang:demonitor(Ref),
-	    receive 
-		{'DOWN', Ref, process, _, _Info} -> 
-		    Res
-	    after 0 ->
-		    Res
-	    end
+	    erlang:demonitor(Ref, [flush]),
+	    Res
     end.
 
 %%%-----------------------------------------------------------------
diff --git a/lib/kernel/src/disk_log.erl b/lib/kernel/src/disk_log.erl
index 0c5af2857e..c238eff12f 100644
--- a/lib/kernel/src/disk_log.erl
+++ b/lib/kernel/src/disk_log.erl
@@ -1914,13 +1914,8 @@ multi_req(Msg, Pids) ->
 			    {'DOWN', Ref, process, Pid, _Info} ->
 				Reply;
 			    {disk_log, Pid, _Reply} ->
-				erlang:demonitor(Ref),
-				receive 
-				    {'DOWN', Ref, process, Pid, _Reason} ->
-					ok
-				after 0 -> 
-					ok
-				end
+				erlang:demonitor(Ref, [flush]),
+				ok
 			end
 		end, {error, nonode}, Refs).
 
@@ -1965,13 +1960,8 @@ monitor_request(Pid, Req) ->
 	    {error, no_such_log};
 	{disk_log, Pid, Reply} when not is_tuple(Reply) orelse
                                     element(2, Reply) =/= disk_log_stopped ->
-	    erlang:demonitor(Ref),
-	    receive 
-		{'DOWN', Ref, process, Pid, _Reason} ->
-		    Reply
-	    after 0 ->
-                    Reply
-	    end
+	    erlang:demonitor(Ref, [flush]),
+	    Reply
     end.
 
 req2(Pid, R) ->
diff --git a/lib/kernel/src/file_io_server.erl b/lib/kernel/src/file_io_server.erl
index fad2ed7fb3..07fb55f390 100644
--- a/lib/kernel/src/file_io_server.erl
+++ b/lib/kernel/src/file_io_server.erl
@@ -92,8 +92,7 @@ do_start(Spawn, Owner, FileName, ModeList) ->
     Mref = erlang:monitor(process, Pid),
     receive
 	{Ref, {error, _Reason} = Error} ->
-	    erlang:demonitor(Mref),
-	    receive {'DOWN', Mref, _, _, _} -> ok after 0 -> ok end,
+	    erlang:demonitor(Mref, [flush]),
 	    Error;
 	{Ref, ok} ->
 	    erlang:demonitor(Mref),
diff --git a/lib/kernel/src/file_server.erl b/lib/kernel/src/file_server.erl
index 49ec6f96cc..d036dbb516 100644
--- a/lib/kernel/src/file_server.erl
+++ b/lib/kernel/src/file_server.erl
@@ -317,8 +317,7 @@ do_start_slave(start, Filer, Name) ->
     SlaveMonitor = erlang:monitor(process, Slave),
     receive
 	{started, Token} ->
-	    erlang:demonitor(SlaveMonitor),
-	    receive {'DOWN', SlaveMonitor, _, _, _} -> ok after 0 -> ok end,
+	    erlang:demonitor(SlaveMonitor, [flush]),
 	    {ok, Slave};
 	{'DOWN', SlaveMonitor, _, _, Reason} ->
 	    exit(Reason)
diff --git a/lib/kernel/src/inet_gethost_native.erl b/lib/kernel/src/inet_gethost_native.erl
index db3e44ce6f..df866660b4 100644
--- a/lib/kernel/src/inet_gethost_native.erl
+++ b/lib/kernel/src/inet_gethost_native.erl
@@ -503,8 +503,7 @@ getit(Req, DefaultName) ->
 			Pid, Reason} ->
 			   {error, Reason}
 		   end,
-	    catch erlang:demonitor(Ref2),
-	    receive {'DOWN',Ref2,_,_,_} -> ok after 0 -> ok end,
+	    catch erlang:demonitor(Ref2, [flush]),
 	    Res2
     end.
 
diff --git a/lib/kernel/src/rpc.erl b/lib/kernel/src/rpc.erl
index 7c965ca384..83e0b59cc2 100644
--- a/lib/kernel/src/rpc.erl
+++ b/lib/kernel/src/rpc.erl
@@ -388,13 +388,8 @@ server_call(Node, Name, ReplyWrapper, Msg)
 		{'DOWN', Ref, _, _, _} ->
 		    {error, nodedown};
 		{ReplyWrapper, Node, Reply} ->
-		    erlang:demonitor(Ref),
-		    receive
-			{'DOWN', Ref, _, _, _} ->
-			    Reply
-		    after 0 ->
-			    Reply
-		    end
+		    erlang:demonitor(Ref, [flush]),
+		    Reply
 	    end
     end.
 
@@ -501,17 +496,6 @@ start_monitor(Node, Name) ->
 	    {Node,erlang:monitor(process, {Name, Node})}
     end.
 
-%% Cancels a monitor started with Ref=erlang:monitor(_, _),
-%% i.e return value {Node, Ref} from start_monitor/2 above.
-unmonitor(Ref) when is_reference(Ref) ->
-    erlang:demonitor(Ref),
-    receive
-	{'DOWN', Ref, _, _, _} ->
-	    true
-    after 0 ->
-	    true
-    end.
-
 
 %% Call apply(M,F,A) on all nodes in parallel
 -spec multicall(Module, Function, Args) -> {ResL, BadNodes} when
@@ -635,10 +619,10 @@ rec_nodes(Name, [{N,R} | Tail], Badnodes, Replies) ->
 	    rec_nodes(Name, Tail, [N|Badnodes], Replies);
 	{?NAME, N, {nonexisting_name, _}} ->  
 	    %% used by sbcast()
-	    unmonitor(R),
+	    erlang:demonitor(R, [flush]),
 	    rec_nodes(Name, Tail, [N|Badnodes], Replies);
 	{Name, N, Reply} ->  %% Name is bound !!!
-	    unmonitor(R),
+	    erlang:demonitor(R, [flush]),
 	    rec_nodes(Name, Tail, Badnodes, [Reply|Replies])
     end.
 
diff --git a/lib/kernel/test/gen_sctp_SUITE.erl b/lib/kernel/test/gen_sctp_SUITE.erl
index 2a886b2efc..c5d8becfd3 100644
--- a/lib/kernel/test/gen_sctp_SUITE.erl
+++ b/lib/kernel/test/gen_sctp_SUITE.erl
@@ -1399,8 +1399,7 @@ s_req(S, Req) ->
 	{'DOWN',Mref,_,_,Error} ->
 	    exit(Error);
 	{S,Mref,Reply} ->
-	    erlang:demonitor(Mref),
-	    receive {'DOWN',Mref,_,_,_} -> ok after 0 -> ok end,
+	    erlang:demonitor(Mref, [flush]),
 	    Reply
     end.
 
diff --git a/lib/orber/src/orber_iiop_outproxy.erl b/lib/orber/src/orber_iiop_outproxy.erl
index 879af8222d..9c4e603753 100644
--- a/lib/orber/src/orber_iiop_outproxy.erl
+++ b/lib/orber/src/orber_iiop_outproxy.erl
@@ -69,13 +69,8 @@ request(Pid, true, Timeout, Msg, RequestId) ->
     gen_server:cast(Pid, {request, Timeout, Msg, RequestId, self(), MRef}),
     receive
 	{MRef, Reply} ->
-	    erlang:demonitor(MRef),
-            receive 
-                {'DOWN', MRef, _, _, _} -> 
-                    Reply
-            after 0 -> 
-                    Reply
-            end;
+	    erlang:demonitor(MRef, [flush]),
+            Reply;
 	{'DOWN', MRef, _, Pid, _Reason} when is_pid(Pid) ->
             receive
 		%% Clear EXIT message from queue
@@ -444,13 +439,7 @@ collect_fragments(GIOPHdr1, InBuffer, Bytes, Proxy, RequestId, MRef) ->
 	%% the reply and send it to the client.
 	{fragment, #giop_message{byte_order = ByteOrder,
 				 message    = Message} = GIOPHdr2, RequestId, MRef} ->
-	    erlang:demonitor(MRef),
-            receive 
-                {'DOWN', MRef, _, _, _} -> 
-		    ok
-            after 0 -> 
-		    ok
-            end,
+	    erlang:demonitor(MRef, [flush]),
 	    case catch cdr_decode:dec_message_header(null, GIOPHdr2, Message) of
 		{_, #fragment_header{}, FragBody, _, _} ->
 		    %% This buffer is all the fragments concatenated.
@@ -484,13 +473,8 @@ Unable to decode Reply or LocateReply header",[?LINE, NewGIOP, Error], ?DEBUG_LE
 	{MRef, {'EXCEPTION', E}} ->
 	    orber:dbg("[~p] orber_iiop:collect_fragments(~p);", 
 		      [?LINE, E], ?DEBUG_LEVEL),
-	    erlang:demonitor(MRef),
-            receive 
-                {'DOWN', MRef, _, _, _} -> 
-		    corba:raise(E)
-            after 0 -> 
-		    corba:raise(E)
-            end;
+	    erlang:demonitor(MRef, [flush]),
+            corba:raise(E);
 	{'DOWN', MRef, _, Proxy, Reason} when is_pid(Proxy) ->
 	    orber:dbg("[~p] orber_iiop:collect_fragments(~p);~n"
 		      "Monitor generated a DOWN message.", 
@@ -511,13 +495,8 @@ clear_queue(Proxy, RequestId, MRef) ->
 	{MRef, RequestId, cancelled} ->
 	    %% This is the last message that the proxy will send
 	    %% after we've cancelled the request.
-	    erlang:demonitor(MRef),
-	    receive 
-		{'DOWN', MRef, _, _, _} -> 
-		    ok
-	    after 0 -> 
-		    ok
-	    end;
+	    erlang:demonitor(MRef, [flush]),
+	    ok;
 	{'DOWN', MRef, _, Proxy, _Reason} ->
 	    %% The proxy terminated. Clear EXIT message from queue
             receive
diff --git a/lib/runtime_tools/src/dbg.erl b/lib/runtime_tools/src/dbg.erl
index 6e3bfe31c6..6b2fb0460f 100644
--- a/lib/runtime_tools/src/dbg.erl
+++ b/lib/runtime_tools/src/dbg.erl
@@ -551,8 +551,7 @@ c(M, F, A, Flags) ->
 		    stop_clear(),
 		    {error, Reason};
 		{Pid, Res} ->
-		    erlang:demonitor(Mref),
-		    receive {'DOWN', Mref, _, _, _} -> ok after 0 -> ok end,
+		    erlang:demonitor(Mref, [flush]),
 		    %% 'sleep' prevents the tracer (recv_all_traces) from
 		    %% receiving garbage {'EXIT',...} when dbg i stopped.
 		    timer:sleep(1),
@@ -592,8 +591,7 @@ req(R) ->
 	{'DOWN', Mref, _, _, _} -> % If server died
 	    exit(dbg_server_crash);
 	{dbg, Reply} ->
-	    erlang:demonitor(Mref),
-	    receive {'DOWN', Mref, _, _, _} -> ok after 0 -> ok end,
+	    erlang:demonitor(Mref, [flush]),
 	    Reply
     end.
 
diff --git a/lib/snmp/src/agent/snmpa_target_cache.erl b/lib/snmp/src/agent/snmpa_target_cache.erl
index 2aa35aa46a..1fcaf82373 100644
--- a/lib/snmp/src/agent/snmpa_target_cache.erl
+++ b/lib/snmp/src/agent/snmpa_target_cache.erl
@@ -21,8 +21,6 @@
 -behaviour(gen_server).
 
 %% External exports
-%% Avoid warning for local function demonitor/1 clashing with autoimported BIF.
--compile({no_auto_import,[demonitor/1]}).
 -export([start_link/2, stop/0, verbosity/1]).
 
 -export([
@@ -213,21 +211,6 @@ do_init(Prio, Opts) ->
 %%     requests will have to wait.
 %% 
 
-monitor(Pid)   -> erlang:monitor(process, Pid).
--ifdef(SNMP_R10).
-demonitor(Ref) -> 
-    erlang:demonitor(Ref),
-    receive
-	{_, Ref, _, _, _} ->
-	    true
-    after 0 ->
-	    true
-    end.
--else.
-demonitor(Ref) -> 
-    erlang:demonitor(Ref, [flush]).
--endif.
-
 
 %% (1) No write_lock active or waiting
 handle_call({lock, read = Type, infinity}, {Pid, _} = From, 
@@ -236,7 +219,7 @@ handle_call({lock, read = Type, infinity}, {Pid, _} = From,
 	  "entry when no waiting or active writer with"
 	  "~n   Pid: ~p"
 	  "~n   Cnt: ~p", [Pid, Cnt]),
-    MonRef = monitor(Pid),
+    MonRef = erlang:monitor(process, Pid),
     Locker = #locker{pid     = Pid, 
                      from    = From,
 		     mon_ref = MonRef, 
@@ -252,7 +235,7 @@ handle_call({lock, read = Type, infinity}, {Pid, _} = From, State) ->
     ?vlog("lock(read, infinity) -> "
 	  "entry when active or waiting write locks with"
 	  "~n   Pid: ~p", [Pid]),
-    MonRef = monitor(Pid),
+    MonRef = erlang:monitor(process, Pid),
     Locker = #locker{pid     = Pid, 
 		     from    = From, 
 		     mon_ref = MonRef, 
@@ -273,7 +256,7 @@ handle_call({lock, write = Type, infinity}, {Pid, _} = From,
     ?vlog("lock(write, infinity) -> "
 	  "entry when no active lockers with"
 	  "~n   Pid: ~p", [Pid]),
-    MonRef = monitor(Pid),
+    MonRef = erlang:monitor(process, Pid),
     Locker = #locker{pid     = Pid, 
                      from    = From,
 		     mon_ref = MonRef, 
@@ -290,7 +273,7 @@ handle_call({lock, write = Type, infinity}, {Pid, _} = From,
     ?vlog("lock(write, infinity) -> "
 	  "entry when active lockers with"
 	  "~n   Pid: ~p", [Pid]),
-    MonRef = monitor(Pid),
+    MonRef = erlang:monitor(process, Pid),
     Locker = #locker{pid     = Pid, 
 		     from    = From, 
 		     mon_ref = MonRef, 
@@ -307,7 +290,7 @@ handle_call({lock, write = Type, infinity}, {Pid, _} = From,
 	    #state{writer = true} = State) ->
     ?vlog("lock(write, infinity) -> entry with"
 	  "~n   Pid: ~p", [Pid]),
-    MonRef = monitor(Pid),
+    MonRef = erlang:monitor(process, Pid),
     Locker = #locker{pid     = Pid, 
 		     from    = From, 
 		     mon_ref = MonRef, 
@@ -429,7 +412,7 @@ handle_cast({unlock, Pid},
 	[#locker{mon_ref = MonRef, type = read}] ->
 	    ?vdebug("unlock -> found read locker"
 		    "~n   MonRef: ~p", [MonRef]),
-	    demonitor(MonRef),
+	    erlang:demonitor(MonRef, [flush]),
 	    ets:delete(?LOCKER_TAB, Pid),
 %% 	    ?vtrace("unlock -> done when"
 %% 		    "~n   Lockers: ~p", [ets:tab2list(?LOCKER_TAB)]),
@@ -437,7 +420,7 @@ handle_cast({unlock, Pid},
 	[#locker{mon_ref = MonRef, type = write}] ->
 	    ?vdebug("unlock -> found write locker"
 		    "~n   MonRef: ~p", [MonRef]),
-	    demonitor(MonRef),
+	    erlang:demonitor(MonRef, [flush]),
 	    ets:delete(?LOCKER_TAB, Pid),
 %% 	    ?vtrace("unlock -> done when"
 %% 		    "~n   Lockers: ~p", [ets:tab2list(?LOCKER_TAB)]),
@@ -459,7 +442,7 @@ handle_cast({unlock, Pid},
 	[#locker{mon_ref = MonRef, type = read}] when (Cnt == 1) ->
 	    ?vdebug("unlock -> found read locker"
 		    "~n   MonRef: ~p", [MonRef]),
-	    demonitor(MonRef),
+	    erlang:demonitor(MonRef, [flush]),
 	    ets:delete(?LOCKER_TAB, Pid),
 	    case active_waiting_writer(Waiting) of
 		{true, StillWaiting} ->
@@ -482,7 +465,7 @@ handle_cast({unlock, Pid},
 	[#locker{mon_ref = MonRef, type = read}] ->
 	    ?vdebug("unlock -> found read locker"
 		    "~n   MonRef: ~p", [MonRef]),
-	    demonitor(MonRef),
+	    erlang:demonitor(MonRef, [flush]),
 	    ets:delete(?LOCKER_TAB, Pid),
 %% 	    ?vtrace("unlock -> done when"
 %% 		    "~n   Lockers: ~p", [ets:tab2list(?LOCKER_TAB)]),
@@ -492,7 +475,7 @@ handle_cast({unlock, Pid},
 	    %% Release the hord (maybe)
 	    ?vdebug("unlock -> found write locker"
 		    "~n   MonRef: ~p", [MonRef]),
-	    demonitor(MonRef),
+	    erlang:demonitor(MonRef, [flush]),
 	    ets:delete(?LOCKER_TAB, Pid),
 	    {Active, StillWaiting, Writer} = 
 		activate_waiting_readers_or_maybe_writer(Waiting),
diff --git a/lib/stdlib/src/dets.erl b/lib/stdlib/src/dets.erl
index 45aef0ea80..50812cc532 100644
--- a/lib/stdlib/src/dets.erl
+++ b/lib/stdlib/src/dets.erl
@@ -1246,13 +1246,8 @@ req(Proc, R) ->
 	{'DOWN', Ref, process, Proc, _Info} ->
             badarg;
 	{Proc, Reply} ->
-	    erlang:demonitor(Ref),
-	    receive 
-		{'DOWN', Ref, process, Proc, _Reason} ->
-                    Reply
-	    after 0 ->
-                    Reply
-	    end
+	    erlang:demonitor(Ref, [flush]),
+	    Reply
     end.
 
 %% Inlined.
diff --git a/lib/stdlib/src/epp.erl b/lib/stdlib/src/epp.erl
index 0a1caa7178..e31cd63f69 100644
--- a/lib/stdlib/src/epp.erl
+++ b/lib/stdlib/src/epp.erl
@@ -1339,8 +1339,7 @@ epp_reply(From, Rep) ->
 wait_epp_reply(Epp, Mref) ->
     receive
 	{epp_reply,Epp,Rep} ->
-	    erlang:demonitor(Mref),
-	    receive {'DOWN',Mref,_,_,_} -> ok after 0 -> ok end,
+	    erlang:demonitor(Mref, [flush]),
 	    Rep;
 	{'DOWN',Mref,_,_,E} ->
 	    receive {epp_reply,Epp,Rep} -> Rep
diff --git a/lib/stdlib/src/gen_server.erl b/lib/stdlib/src/gen_server.erl
index 9c4b95acf6..30a81ade49 100644
--- a/lib/stdlib/src/gen_server.erl
+++ b/lib/stdlib/src/gen_server.erl
@@ -472,11 +472,11 @@ rec_nodes(Tag, [{N,R}|Tail], Name, Badnodes, Replies, Time, TimerId ) ->
 	{'DOWN', R, _, _, _} ->
 	    rec_nodes(Tag, Tail, Name, [N|Badnodes], Replies, Time, TimerId);
 	{{Tag, N}, Reply} ->  %% Tag is bound !!!
-	    unmonitor(R), 
+	    erlang:demonitor(R, [flush]),
 	    rec_nodes(Tag, Tail, Name, Badnodes, 
 		      [{N,Reply}|Replies], Time, TimerId);
 	{timeout, TimerId, _} ->	
-	    unmonitor(R),
+	    erlang:demonitor(R, [flush]),
 	    %% Collect all replies that already have arrived
 	    rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies)
     end;
@@ -527,10 +527,10 @@ rec_nodes_rest(Tag, [{N,R}|Tail], Name, Badnodes, Replies) ->
 	{'DOWN', R, _, _, _} ->
 	    rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies);
 	{{Tag, N}, Reply} -> %% Tag is bound !!!
-	    unmonitor(R),
+	    erlang:demonitor(R, [flush]),
 	    rec_nodes_rest(Tag, Tail, Name, Badnodes, [{N,Reply}|Replies])
     after 0 ->
-	    unmonitor(R),
+	    erlang:demonitor(R, [flush]),
 	    rec_nodes_rest(Tag, Tail, Name, [N|Badnodes], Replies)
     end;
 rec_nodes_rest(Tag, [N|Tail], Name, Badnodes, Replies) ->
@@ -572,16 +572,6 @@ start_monitor(Node, Name) when is_atom(Node), is_atom(Name) ->
 	    end
     end.
 
-%% Cancels a monitor started with Ref=erlang:monitor(_, _).
-unmonitor(Ref) when is_reference(Ref) ->
-    erlang:demonitor(Ref),
-    receive
-	{'DOWN', Ref, _, _, _} ->
-	    true
-    after 0 ->
-	    true
-    end.
-
 %%% ---------------------------------------------------
 %%% Message handling functions
 %%% ---------------------------------------------------
diff --git a/lib/stdlib/src/io.erl b/lib/stdlib/src/io.erl
index c92e9e3ade..53728237ca 100644
--- a/lib/stdlib/src/io.erl
+++ b/lib/stdlib/src/io.erl
@@ -598,11 +598,7 @@ default_output() ->
 wait_io_mon_reply(From, Mref) ->
     receive
 	{io_reply, From, Reply} ->
-	    erlang:demonitor(Mref),
-	    receive 
-		{'DOWN', Mref, _, _, _} -> true
-	    after 0 -> true
-	    end,
+	    erlang:demonitor(Mref, [flush]),
 	    Reply;
 	{'EXIT', From, _What} ->
 	    receive
diff --git a/lib/tools/src/fprof.erl b/lib/tools/src/fprof.erl
index 4cbb910f11..877218bda0 100644
--- a/lib/tools/src/fprof.erl
+++ b/lib/tools/src/fprof.erl
@@ -1226,10 +1226,7 @@ spawn_3step(Spawn, FunPrelude, FunAck, FunBody)
 		  MRef = erlang:monitor(process, Parent),
 		  receive
 		      {Parent, Ref, Go} ->
-			  erlang:demonitor(MRef),
-			  receive {'DOWN', MRef, _, _, _} -> ok 
-			  after 0 -> ok
-			  end,
+			  erlang:demonitor(MRef, [flush]),
 			  FunBody(Go);
 		      {'DOWN', MRef, _, _, _} ->
 			  ok
@@ -1238,8 +1235,7 @@ spawn_3step(Spawn, FunPrelude, FunAck, FunBody)
     MRef = erlang:monitor(process, Child),
     receive
 	{Child, Ref, Ack} ->
-	    erlang:demonitor(MRef),
-	    receive {'DOWN', MRef, _, _, _} -> ok after 0 -> ok end,
+	    erlang:demonitor(MRef, [flush]),
 	    try FunAck(Ack) of
 		{Result, Go} ->
 		    catch Child ! {Parent, Ref, Go},