Introduce a new time API

The old time API is based on erlang:now/0. The major issue with
erlang:now/0 is that it was intended to be used for so many
unrelated things. This tied these unrelated operations together
and unnecessarily caused performance, scalability as well as
accuracy, and precision issues for operations that do not need
to have such issues. The new API spreads different functionality
over multiple functions in order to improve on this.

The new API consists of a number of new BIFs:
- erlang:convert_time_unit/3
- erlang:monotonic_time/0
- erlang:monotonic_time/1
- erlang:system_time/0
- erlang:system_time/1
- erlang:time_offset/0
- erlang:time_offset/1
- erlang:timestamp/0
- erlang:unique_integer/0
- erlang:unique_integer/1
- os:system_time/0
- os:system_time/1

and a number of extensions of existing BIFs:
- erlang:monitor(time_offset, clock_service)
- erlang:system_flag(time_offset, finalize)
- erlang:system_info(os_monotonic_time_source)
- erlang:system_info(time_offset)
- erlang:system_info(time_warp_mode)
- erlang:system_info(time_correction)
- erlang:system_info(start_time)

See the "Time and Time Correction in Erlang" chapter of the
ERTS User's Guide for more information.

1 files changed, 110 insertions, 3 deletions

diff --git a/erts/emulator/test/monitor_SUITE.erl b/erts/emulator/test/monitor_SUITE.erl
index aec59867d8..07e2862b2a 100644
--- a/erts/emulator/test/monitor_SUITE.erl
+++ b/erts/emulator/test/monitor_SUITE.erl
@@ -26,7 +26,8 @@
 	 case_1/1, case_1a/1, case_2/1, case_2a/1, mon_e_1/1, demon_e_1/1, demon_1/1,
 	 demon_2/1, demon_3/1, demonitor_flush/1,
 	 local_remove_monitor/1, remote_remove_monitor/1, mon_1/1, mon_2/1,
-	 large_exit/1, list_cleanup/1, mixer/1, named_down/1, otp_5827/1]).
+	 large_exit/1, list_cleanup/1, mixer/1, named_down/1, otp_5827/1,
+	 monitor_time_offset/1]).
 
 -export([init_per_testcase/2, end_per_testcase/2]).
 
@@ -38,7 +39,8 @@ all() ->
     [case_1, case_1a, case_2, case_2a, mon_e_1, demon_e_1,
      demon_1, mon_1, mon_2, demon_2, demon_3,
      demonitor_flush, {group, remove_monitor}, large_exit,
-     list_cleanup, mixer, named_down, otp_5827].
+     list_cleanup, mixer, named_down, otp_5827,
+     monitor_time_offset].
 
 groups() -> 
     [{remove_monitor, [],
@@ -59,7 +61,7 @@ end_per_group(_GroupName, Config) ->
 
 init_per_testcase(Func, Config) when is_atom(Func), is_list(Config) ->
     Dog=?t:timetrap(?t:minutes(15)),
-    [{watchdog, Dog}|Config].
+    [{watchdog, Dog},{testcase, Func}|Config].
 
 end_per_testcase(_Func, Config) ->
     Dog=?config(watchdog, Config),
@@ -837,6 +839,89 @@ otp_5827(Config) when is_list(Config) ->
 		  ?line ?t:fail("erlang:monitor/2 hangs")
 	  end.
 
+monitor_time_offset(Config) when is_list(Config) ->
+    {ok, Node} = start_node(Config, "+C single_time_warp"),
+    Me = self(),
+    PMs = lists:map(fun (_) ->
+			    Pid = spawn(Node,
+					fun () ->
+						check_monitor_time_offset(Me)
+					end),
+			    {Pid, erlang:monitor(process, Pid)}
+		    end,
+		    lists:seq(1, 100)),
+    lists:foreach(fun ({P, _M}) ->
+			  P ! check_no_change_message
+		  end, PMs),
+    lists:foreach(fun ({P, M}) ->
+			  receive
+			      {no_change_message_received, P} ->
+				  ok;
+			      {'DOWN', M, process, P, Reason} ->
+				  ?t:fail(Reason)
+			  end
+		  end, PMs),
+    preliminary = rpc:call(Node, erlang, system_flag, [time_offset, finalize]),
+    lists:foreach(fun ({P, M}) ->
+			  receive
+			      {change_messages_received, P} ->
+				  erlang:demonitor(M, [flush]);
+			      {'DOWN', M, process, P, Reason} ->
+				  ?t:fail(Reason)
+			  end
+		  end, PMs),
+    stop_node(Node),
+    ok.
+
+check_monitor_time_offset(Leader) ->
+    Mon1 = erlang:monitor(time_offset, clock_service),
+    Mon2 = erlang:monitor(time_offset, clock_service),
+    Mon3 = erlang:monitor(time_offset, clock_service),
+    Mon4 = erlang:monitor(time_offset, clock_service),
+
+    erlang:demonitor(Mon2, [flush]),
+    
+    Mon5 = erlang:monitor(time_offset, clock_service),
+    Mon6 = erlang:monitor(time_offset, clock_service),
+    Mon7 = erlang:monitor(time_offset, clock_service),
+
+    receive check_no_change_message -> ok end,
+    receive
+	{'CHANGE', _, time_offset, clock_service, _} ->
+	    exit(unexpected_change_message_received)
+    after 0 ->
+	    Leader ! {no_change_message_received, self()}
+    end,
+    receive after 100 -> ok end,
+    erlang:demonitor(Mon4, [flush]),
+    receive
+	{'CHANGE', Mon3, time_offset, clock_service, _} ->
+	    ok
+    end,
+    receive
+	{'CHANGE', Mon6, time_offset, clock_service, _} ->
+	    ok
+    end,
+    erlang:demonitor(Mon5, [flush]),
+    receive
+	{'CHANGE', Mon7, time_offset, clock_service, _} ->
+	    ok
+    end,
+    receive
+	{'CHANGE', Mon1, time_offset, clock_service, _} ->
+	    ok
+    end,
+    receive
+	{'CHANGE', _, time_offset, clock_service, _} ->
+	    exit(unexpected_change_message_received)
+    after 1000 ->
+	    ok
+    end,
+    Leader ! {change_messages_received, self()}.
+
+%%
+%% ...
+%%
 
 wait_for_m(_,_,0) ->
     exit(monitor_wait_timeout);
@@ -959,3 +1044,25 @@ generate(_Fun, 0) ->
     [];
 generate(Fun, N) ->
     [Fun() | generate(Fun, N-1)].
+
+start_node(Config) ->
+    start_node(Config, "").
+
+start_node(Config, Args) ->
+    TestCase = ?config(testcase, Config),
+    PA = filename:dirname(code:which(?MODULE)),
+    ESTime = erlang:monotonic_time(1) + erlang:time_offset(1),
+    Unique = erlang:unique_integer([positive]),
+    Name = list_to_atom(atom_to_list(?MODULE)
+			++ "-"
+			++ atom_to_list(TestCase)
+			++ "-"
+			++ integer_to_list(ESTime)
+			++ "-"
+			++ integer_to_list(Unique)),
+    test_server:start_node(Name,
+			   slave,
+			   [{args, "-pa " ++ PA ++ " " ++ Args}]).
+
+stop_node(Node) ->
+    test_server:stop_node(Node).