From d4341cd249d728174fce580bd018e1e8b402d161 Mon Sep 17 00:00:00 2001 From: Dan Gudmundsson Date: Mon, 20 Nov 2017 15:23:24 +0100 Subject: kernel: add a resource reference counter System resources/functionality may need to be reference counted to be handled correctly when used or enabled/disabled from more than one process or application. It is easier to handle this in erlang code than in erts, so make a process that deals with the housekeeping. --- lib/kernel/src/Makefile | 1 + lib/kernel/src/kernel.app.src | 2 + lib/kernel/src/kernel.erl | 11 +++- lib/kernel/src/kernel_refc.erl | 139 +++++++++++++++++++++++++++++++++++++++ lib/kernel/test/kernel_SUITE.erl | 69 ++++++++++++++++++- 5 files changed, 218 insertions(+), 4 deletions(-) create mode 100644 lib/kernel/src/kernel_refc.erl (limited to 'lib') diff --git a/lib/kernel/src/Makefile b/lib/kernel/src/Makefile index 5946620f0f..acfcca55e5 100644 --- a/lib/kernel/src/Makefile +++ b/lib/kernel/src/Makefile @@ -106,6 +106,7 @@ MODULES = \ inet_sctp \ kernel \ kernel_config \ + kernel_refc \ local_udp \ local_tcp \ net \ diff --git a/lib/kernel/src/kernel.app.src b/lib/kernel/src/kernel.app.src index 080b11fc4d..3136db8267 100644 --- a/lib/kernel/src/kernel.app.src +++ b/lib/kernel/src/kernel.app.src @@ -57,6 +57,7 @@ inet_tcp_dist, kernel, kernel_config, + kernel_refc, local_tcp, local_udp, net, @@ -107,6 +108,7 @@ heart, init, kernel_config, + kernel_refc, kernel_sup, net_kernel, net_sup, diff --git a/lib/kernel/src/kernel.erl b/lib/kernel/src/kernel.erl index cba57088ec..0382764b39 100644 --- a/lib/kernel/src/kernel.erl +++ b/lib/kernel/src/kernel.erl @@ -111,6 +111,13 @@ init([]) -> type => worker, modules => [kernel_config]}, + RefC = #{id => kernel_refc, + start => {kernel_refc, start_link, []}, + restart => permanent, + shutdown => 2000, + type => worker, + modules => [kernel_refc]}, + Code = #{id => code_server, start => {code, start_link, []}, restart => permanent, @@ -148,7 +155,7 @@ init([]) -> case init:get_argument(mode) of {ok, [["minimal"]]} -> - {ok, {SupFlags, [Code, File, StdError, User, Config, SafeSup]}}; + {ok, {SupFlags, [Code, File, StdError, User, Config, RefC, SafeSup]}}; _ -> Rpc = #{id => rex, start => {rpc, start_link, []}, @@ -199,7 +206,7 @@ init([]) -> {ok, {SupFlags, [Code, Rpc, Global, InetDb | DistAC] ++ [NetSup, GlGroup, File, SigSrv, - StdError, User, Config, SafeSup] ++ Timer}} + StdError, User, Config, RefC, SafeSup] ++ Timer}} end; init(safe) -> SupFlags = #{strategy => one_for_one, diff --git a/lib/kernel/src/kernel_refc.erl b/lib/kernel/src/kernel_refc.erl new file mode 100644 index 0000000000..3ad68e9ff9 --- /dev/null +++ b/lib/kernel/src/kernel_refc.erl @@ -0,0 +1,139 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2017. All Rights Reserved. +%% +%% Licensed under the Apache License, Version 2.0 (the "License"); +%% you may not use this file except in compliance with the License. +%% You may obtain a copy of the License at +%% +%% http://www.apache.org/licenses/LICENSE-2.0 +%% +%% Unless required by applicable law or agreed to in writing, software +%% distributed under the License is distributed on an "AS IS" BASIS, +%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +%% See the License for the specific language governing permissions and +%% limitations under the License. +%% +%% %CopyrightEnd% +%% +-module(kernel_refc). + +-behaviour(gen_server). + +%% External exports +-export([start_link/0, scheduler_wall_time/1]). +%% Internal exports +-export([init/1, handle_info/2, terminate/2]). +-export([handle_call/3, handle_cast/2, code_change/3]). + +%%%----------------------------------------------------------------- +%%% This module implements a process that handles reference counters for +%%% various erts or other kernel resources which needs reference counting. +%%% +%%% Should not be documented nor used directly by user applications. +%%%----------------------------------------------------------------- +start_link() -> + gen_server:start_link({local,kernel_refc}, kernel_refc, [], []). + +-spec scheduler_wall_time(boolean()) -> boolean(). +scheduler_wall_time(Bool) -> + gen_server:call(kernel_refc, {scheduler_wall_time, self(), Bool}). + +%%----------------------------------------------------------------- +%% Callback functions from gen_server +%%----------------------------------------------------------------- + +-spec init([]) -> {'ok', map()} | {'stop', term()}. + +init([]) -> + resource(scheduler_wall_time, false), + {ok, #{scheduler_wall_time=>#{}}}. + +-spec handle_call(term(), term(), State) -> {'reply', term(), State}. +handle_call({What, Who, false}, _From, State) -> + {Reply, Cnt} = do_stop(What, maps:get(What, State), Who), + {reply, Reply, State#{What:=Cnt}}; +handle_call({What, Who, true}, _From, State) -> + {Reply, Cnt} = do_start(What, maps:get(What, State), Who), + {reply, Reply, State#{What:=Cnt}}; +handle_call(_, _From, State) -> + {reply, badarg, State}. + +-spec handle_cast(term(), State) -> {'noreply', State}. +handle_cast(_, State) -> + {noreply, State}. + +-spec handle_info(term(), State) -> {'noreply', State}. +handle_info({'DOWN', _Ref, process, Pid, _}, State) -> + Cleanup = fun(Resource, Cnts) -> + cleanup(Resource, Cnts, Pid) + end, + {noreply, maps:map(Cleanup, State)}; +handle_info(_, State) -> + {noreply, State}. + +-spec terminate(term(), term()) -> 'ok'. +terminate(_Reason, _State) -> + ok. + +-spec code_change(term(), State, term()) -> {'ok', State}. +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + +%%----------------------------------------------------------------- +%% Internal functions +%%----------------------------------------------------------------- + +do_start(Resource, Cnt, Pid) -> + case maps:get(Pid, Cnt, undefined) of + undefined -> + Ref = erlang:monitor(process, Pid), + case any(Cnt) of + true -> + {true, Cnt#{Pid=>{1, Ref}}}; + false -> + resource(Resource, true), + {false, Cnt#{Pid=>{1, Ref}}} + end; + {N, Ref} -> + {true, Cnt#{Pid=>{N+1, Ref}}} + end. + +do_stop(Resource, Cnt0, Pid) -> + case maps:get(Pid, Cnt0, undefined) of + undefined -> + {any(Cnt0), Cnt0}; + {1, Ref} -> + erlang:demonitor(Ref, [flush]), + Cnt = maps:remove(Pid, Cnt0), + case any(Cnt) of + true -> + {true, Cnt}; + false -> + resource(Resource, false), + {true, Cnt} + end; + {N, Ref} -> + {true, Cnt0#{Pid=>{N-1, Ref}}} + end. + +cleanup(Resource, Cnt0, Pid) -> + case maps:is_key(Pid, Cnt0) of + true -> + Cnt = maps:remove(Pid, Cnt0), + case any(Cnt) of + true -> + Cnt; + false -> + resource(Resource, false), + Cnt + end; + false -> + Cnt0 + end. + +any(Cnt) -> maps:size(Cnt) > 0. + +resource(scheduler_wall_time, Enable) -> + _ = erlang:system_flag(scheduler_wall_time, Enable). diff --git a/lib/kernel/test/kernel_SUITE.erl b/lib/kernel/test/kernel_SUITE.erl index da56359294..7898988dbe 100644 --- a/lib/kernel/test/kernel_SUITE.erl +++ b/lib/kernel/test/kernel_SUITE.erl @@ -30,14 +30,14 @@ -export([init_per_testcase/2, end_per_testcase/2]). %% Test cases must be exported. --export([app_test/1, appup_test/1]). +-export([app_test/1, appup_test/1, refc/1]). suite() -> [{ct_hooks,[ts_install_cth]}, {timetrap,{minutes,2}}]. all() -> - [app_test, appup_test]. + [app_test, appup_test, refc]. groups() -> []. @@ -163,3 +163,68 @@ check_appup([Vsn|Vsns],Instrs,Expected) -> end; check_appup([],_,_) -> ok. + +%%% Check that refc module handles the counters as expected +refc(_Config) -> + Enable = fun(Enable) -> erlang:system_flag(scheduler_wall_time, Enable) end, + IsOn = fun() -> undefined /= erlang:statistics(scheduler_wall_time) end, + Tester = self(), + Loop = fun Loop() -> + receive + die -> normal; + {apply, Bool} -> + Res = Enable(Bool), + Tester ! {self(), Res}, + Loop() + end + end, + + %% Counter should be 0 + false = Enable(false), + + false = Enable(true), + true = Enable(true), + true = Enable(false), + true = Enable(false), + + %% Counter should be 0 + false = IsOn(), + + P1 = spawn_link(Loop), + P1 ! {apply, true}, + receive {P1, R1} -> false = R1 end, + + %% P1 has turned it on counter should be one + true = IsOn(), + true = Enable(true), + true = Enable(false), + true = IsOn(), + + P1 ! {apply, false}, + receive {P1, R2} -> true = R2 end, + false = IsOn(), + + P1 ! {apply, true}, + receive {P1, R3} -> false = R3 end, + true = IsOn(), + true = Enable(false), + + + P1 ! die, + timer:sleep(100), + false = IsOn(), + false = Enable(false), + + P2 = spawn_link(Loop), + P2 ! {apply, true}, + receive {P2, R4} -> false = R4 end, + true = IsOn(), + P2 ! {apply, true}, + receive {P2, R5} -> true = R5 end, + true = IsOn(), + + P2 ! die, + timer:sleep(100), + false = IsOn(), + + ok. -- cgit v1.2.3