Merge branch 'john/erts/kqueue-stdin-polling/OTP-15169/ERL-647' into maint-21

* john/erts/kqueue-stdin-polling/OTP-15169/ERL-647:
  Use fallback pollset for stdin and friends when using kqueue

2 files changed, 41 insertions, 0 deletions

diff --git a/erts/emulator/sys/common/erl_poll.c b/erts/emulator/sys/common/erl_poll.c
index 70b5532af9..b4d1575ee5 100644
--- a/erts/emulator/sys/common/erl_poll.c
+++ b/erts/emulator/sys/common/erl_poll.c
@@ -803,6 +803,23 @@ update_pollset(ErtsPollSet *ps, int fd, ErtsPollOp op, ErtsPollEvents events)
     struct kevent evts[2];
     struct timespec ts = {0, 0};
 
+    if (op == ERTS_POLL_OP_ADD) {
+        /* This is a hack to make the "noshell" option work; kqueue can poll
+         * these fds but will not report EV_EOF, so we return NVAL to use the
+         * fallback instead.
+         *
+         * This may be common to all pipes but we have no way to tell whether
+         * an fd is a pipe or not. */
+        switch (fd) {
+        case STDIN_FILENO:
+        case STDOUT_FILENO:
+        case STDERR_FILENO:
+            return ERTS_POLL_EV_NVAL;
+        default:
+            break;
+        }
+    }
+
 #if defined(EV_DISPATCH) && !defined(__OpenBSD__)
     /* If we have EV_DISPATCH we use it, unless we are on OpenBSD as the
        behavior of EV_EOF seems to be edge triggered there and we need it
diff --git a/erts/emulator/test/driver_SUITE.erl b/erts/emulator/test/driver_SUITE.erl
index 7aff3a6ea1..6f5d639d04 100644
--- a/erts/emulator/test/driver_SUITE.erl
+++ b/erts/emulator/test/driver_SUITE.erl
@@ -81,6 +81,7 @@
          thr_msg_blast/1,
          consume_timeslice/1,
          env/1,
+         poll_pipe/1,
          z_test/1]).
 
 -export([bin_prefix/2]).
@@ -168,6 +169,7 @@ all() -> %% Keep a_test first and z_test last...
      thr_msg_blast,
      consume_timeslice,
      env,
+     poll_pipe,
      z_test].
 
 groups() -> 
@@ -2693,3 +2695,25 @@ rpc(Config, Fun) ->
                     ct:fail(Other)
             end
     end.
+
+poll_pipe(Config) when is_list(Config) ->
+    %% ERL-647; we wouldn't see any events on EOF when polling a pipe using
+    %% kqueue(2).
+    case os:type() of
+        {unix, _} ->
+            Command = "erl -noshell -eval "
+                      "'\"DATA\n\" = io:get_line(\"\"),"
+                      "eof = io:get_line(\"\"),"
+                      "halt()' <<< 'DATA'",
+            Ref = make_ref(),
+            Self = self(),
+            Pid = spawn(fun() -> os:cmd(Command), Self ! Ref end),
+            receive
+                Ref -> ok
+            after 5000 ->
+                exit(Pid, kill),
+                ct:fail("Stuck reading from stdin.")
+            end;
+        _ ->
+            {skipped, "Unix-only test"}
+    end.