Merge branch 'raimo/race-in-prim_inet-close/OTP-10497' into maint

* raimo/race-in-prim_inet-close/OTP-10497:
  Improve solution

2 files changed, 26 insertions, 2 deletions

diff --git a/erts/preloaded/ebin/prim_inet.beam b/erts/preloaded/ebin/prim_inet.beam
index ef305ae1e9..8638ef677e 100644
--- a/erts/preloaded/ebin/prim_inet.beam
+++ b/erts/preloaded/ebin/prim_inet.beam
diff --git a/erts/preloaded/src/prim_inet.erl b/erts/preloaded/src/prim_inet.erl
index 36a650cb5c..fb1269cf91 100644
--- a/erts/preloaded/src/prim_inet.erl
+++ b/erts/preloaded/src/prim_inet.erl
@@ -177,8 +177,32 @@ close_pend_loop(S, N) ->
     end.
 
 close_port(S) ->
-    catch erlang:port_close(S),
-    receive {'EXIT',S,_} -> ok after 0 -> ok end.
+    case erlang:process_info(self(), trap_exit) of
+	{trap_exit,true} ->
+	    %% Ensure exit message and consume it
+	    link(S),
+	    %% This is still not a perfect solution.
+	    %%
+	    %% The problem is to close the port and consume any exit
+	    %% message while not knowing if this process traps exit
+	    %% nor if this process has a link to the port. Here we
+	    %% just knows that this process traps exit.
+	    %%
+	    %% If we right here get killed for some reason that exit
+	    %% signal will propagate to the port and onwards to anyone
+	    %% that is linked to the port. E.g when we close a socket
+	    %% that is not ours.
+	    %%
+	    %% The problem can be solved with lists:member on our link
+	    %% list but we deem that as potentially too expensive. We
+	    %% need an is_linked/1 function or guard, or we need
+	    %% a port_close function that can atomically unlink...
+	    catch erlang:port_close(S),
+	    receive {'EXIT',S,_} -> ok end;
+	{trap_exit,false} ->
+	    catch erlang:port_close(S),
+	    ok
+    end.
 
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