From 5a42fa760c2d908c0724a6e49a1f25a82b5b7792 Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Wed, 14 Jun 2017 17:22:13 +0200
Subject: erts: Add tests to detect port close race

---
 erts/emulator/test/port_SUITE.erl             | 40 +++++++++++++++++++++++++++
 erts/emulator/test/port_SUITE_data/echo_drv.c | 31 ++++++++++++++++++---
 2 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/erts/emulator/test/port_SUITE.erl b/erts/emulator/test/port_SUITE.erl
index 23594aa8c4..3a2243f553 100644
--- a/erts/emulator/test/port_SUITE.erl
+++ b/erts/emulator/test/port_SUITE.erl
@@ -86,6 +86,7 @@
     cd_relative/1,
     close_deaf_port/1,
     count_fds/1,
+    dropped_commands/1,
     dying_port/1,
     env/1,
     eof/1,
@@ -548,6 +549,45 @@ make_dying_port(Config) when is_list(Config) ->
     Command = lists:concat([PortTest, " -h0 -d -q"]),
     open_port({spawn, Command}, [stream]).
 
+%% Test that dropped port_commands work correctly.
+%% This used to cause a segfault.
+%%
+%% This testcase creates a port and then lets many processes
+%% do parallel commands to it. After a while it closes the
+%% port and we are trying to catch the race when doing a
+%% command while the port is closing.
+dropped_commands(Config) ->
+    %% Test with output callback
+    dropped_commands(Config, false, {self(), {command, "1"}}),
+    %% Test with outputv callback
+    dropped_commands(Config, true, {self(), {command, "1"}}).
+
+dropped_commands(Config, Outputv, Cmd) ->
+    Path = proplists:get_value(data_dir, Config),
+    os:putenv("ECHO_DRV_USE_OUTPUTV", atom_to_list(Outputv)),
+    ok = load_driver(Path, "echo_drv"),
+    [dropped_commands_test(Cmd) || _ <- lists:seq(1, 100)],
+    timer:sleep(100),
+    erl_ddll:unload_driver("echo_drv"),
+    ok.
+
+dropped_commands_test(Cmd) ->
+    Port = erlang:open_port({spawn_driver, "echo_drv"}, [{parallelism, true}]),
+    spawn_monitor(
+      fun() ->
+              [spawn_link(fun() -> spin(Port, Cmd) end) || _ <- lists:seq(1,8)],
+              timer:sleep(5),
+              port_close(Port),
+              timer:sleep(5),
+              exit(nok)
+      end),
+    receive _M -> timer:sleep(5) end.
+
+spin(P, Cmd) ->
+    P ! Cmd,
+    spin(P, Cmd).
+
+
 %% Tests that port program with complete path (but without any
 %% .exe extension) can be started, even if there is a file with
 %% the same name but without the extension in the same directory.
diff --git a/erts/emulator/test/port_SUITE_data/echo_drv.c b/erts/emulator/test/port_SUITE_data/echo_drv.c
index 1d39c6a00c..b4370f6455 100644
--- a/erts/emulator/test/port_SUITE_data/echo_drv.c
+++ b/erts/emulator/test/port_SUITE_data/echo_drv.c
@@ -18,8 +18,11 @@ typedef struct _erl_drv_data EchoDrvData;
 
 static EchoDrvData *echo_drv_start(ErlDrvPort port, char *command);
 static void         echo_drv_stop(EchoDrvData *data_p);
-static void         echo_drv_output(ErlDrvData drv_data, char *buf,
-				    ErlDrvSizeT len);
+static void         echo_drv_output(ErlDrvData drv_data, char *buf, ErlDrvSizeT len);
+static ErlDrvSSizeT echo_control(ErlDrvData drv_data,
+                                 unsigned int command, char *buf,
+                                 ErlDrvSizeT len, char **rbuf, ErlDrvSizeT rlen);
+static void         echo_outputv(ErlDrvData drv_data, ErlIOVec *ev);
 static void         echo_drv_finish(void);
 
 static ErlDrvEntry echo_drv_entry = { 
@@ -32,9 +35,9 @@ static ErlDrvEntry echo_drv_entry = {
     "echo_drv",
     echo_drv_finish,
     NULL, /* handle */
-    NULL, /* control */
+    echo_control, /* control */
     NULL, /* timeout */
-    NULL, /* outputv */
+    echo_outputv, /* outputv */
     NULL, /* ready_async */
     NULL,
     NULL,
@@ -56,6 +59,14 @@ static ErlDrvEntry echo_drv_entry = {
 
 DRIVER_INIT(echo_drv)
 {
+    char buf[10];
+    size_t bufsz = sizeof(buf);
+    char *use_outputv;
+    use_outputv = (erl_drv_getenv("ECHO_DRV_USE_OUTPUTV", buf, &bufsz) == 0
+		   ? buf
+		   : "false");
+    if (strcmp(use_outputv, "true") != 0)
+	echo_drv_entry.outputv = NULL;
     return &echo_drv_entry;
 }
 
@@ -87,3 +98,15 @@ static void echo_drv_output(ErlDrvData drv_data, char *buf, ErlDrvSizeT len) {
 
 static void echo_drv_finish() {
 }
+
+static ErlDrvSSizeT echo_control(ErlDrvData drv_data,
+                                 unsigned int command, char *buf,
+                                 ErlDrvSizeT len, char **rbuf, ErlDrvSizeT rlen)
+{
+    return 0;
+}
+
+static void echo_outputv(ErlDrvData drv_data, ErlIOVec *ev)
+{
+    return;
+}
-- 
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