From 3e580e039a8eb2467c638503bc526116fe829fec Mon Sep 17 00:00:00 2001
From: Sverker Eriksson <sverker@erlang.org>
Date: Fri, 2 Mar 2018 16:56:13 +0100
Subject: kernel,stdlib: Remove obsolete use of send with 'noconnect'

as workarounds to avoid blocking auto-connect,
which is now asynchronous in OTP-21.

Also changed old catch to more efficient try-catch.
---
 lib/stdlib/src/gen.erl        | 45 ++++++++++++++++++++-----------------------
 lib/stdlib/src/gen_server.erl | 11 +++++------
 lib/stdlib/src/gen_statem.erl | 13 ++++---------
 3 files changed, 30 insertions(+), 39 deletions(-)

(limited to 'lib/stdlib/src')

diff --git a/lib/stdlib/src/gen.erl b/lib/stdlib/src/gen.erl
index dc957b4d4e..293cb98ad2 100644
--- a/lib/stdlib/src/gen.erl
+++ b/lib/stdlib/src/gen.erl
@@ -159,30 +159,27 @@ call(Process, Label, Request, Timeout)
 
 do_call(Process, Label, Request, Timeout) ->
     Mref = erlang:monitor(process, Process),
-	    %% If the monitor/2 call failed to set up a connection to a
-	    %% remote node, we don't want the '!' operator to attempt
-	    %% to set up the connection again. (If the monitor/2 call
-	    %% failed due to an expired timeout, '!' too would probably
-	    %% have to wait for the timeout to expire.) Therefore,
-	    %% use erlang:send/3 with the 'noconnect' option so that it
-	    %% will fail immediately if there is no connection to the
-	    %% remote node.
-
-	    catch erlang:send(Process, {Label, {self(), Mref}, Request},
-		  [noconnect]),
-	    receive
-		{Mref, Reply} ->
-		    erlang:demonitor(Mref, [flush]),
-		    {ok, Reply};
-		{'DOWN', Mref, _, _, noconnection} ->
-		    Node = get_node(Process),
-		    exit({nodedown, Node});
-		{'DOWN', Mref, _, _, Reason} ->
-		    exit(Reason)
-	    after Timeout ->
-		    erlang:demonitor(Mref, [flush]),
-		    exit(timeout)
-	    end.
+    %% OTP-21:
+    %% Auto-connect is asynchronous. But we still use 'noconnect' to make sure
+    %% we send on the monitored connection, and not trigger a new auto-connect.
+    try erlang:send(Process, {Label, {self(), Mref}, Request}, [noconnect])
+    catch
+        error:_ -> ok
+    end,
+
+    receive
+        {Mref, Reply} ->
+            erlang:demonitor(Mref, [flush]),
+            {ok, Reply};
+        {'DOWN', Mref, _, _, noconnection} ->
+            Node = get_node(Process),
+            exit({nodedown, Node});
+        {'DOWN', Mref, _, _, Reason} ->
+            exit(Reason)
+    after Timeout ->
+            erlang:demonitor(Mref, [flush]),
+            exit(timeout)
+    end.
 
 get_node(Process) ->
     %% We trust the arguments to be correct, i.e
diff --git a/lib/stdlib/src/gen_server.erl b/lib/stdlib/src/gen_server.erl
index 77a46419f6..f29314d0a2 100644
--- a/lib/stdlib/src/gen_server.erl
+++ b/lib/stdlib/src/gen_server.erl
@@ -437,12 +437,11 @@ decode_msg(Msg, Parent, Name, State, Mod, Time, HibernateAfterTimeout, Debug, Hi
 %%% Send/receive functions
 %%% ---------------------------------------------------
 do_send(Dest, Msg) ->
-    case catch erlang:send(Dest, Msg, [noconnect]) of
-	noconnect ->
-	    spawn(erlang, send, [Dest,Msg]);
-	Other ->
-	    Other
-    end.
+    try erlang:send(Dest, Msg)
+    catch
+        error:_ -> ok
+    end,
+    ok.
 
 do_multi_call(Nodes, Name, Req, infinity) ->
     Tag = make_ref(),
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index f95b2ea9cd..9dc360a289 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -641,16 +641,11 @@ replies([]) ->
 
 %% Might actually not send the message in case of caught exception
 send(Proc, Msg) ->
-    try erlang:send(Proc, Msg, [noconnect]) of
-	noconnect ->
-	    _ = spawn(erlang, send, [Proc,Msg]),
-	    ok;
-	ok ->
-	    ok
+    try erlang:send(Proc, Msg)
     catch
-	_:_ ->
-	    ok
-    end.
+        error:_ -> ok
+    end,
+    ok.
 
 %% Here the init_it/6 and enter_loop/5,6,7 functions converge
 enter(Module, Opts, State, Data, Server, Actions, Parent) ->
-- 
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