From 0a4834e59f2aac7b76331410bcee641d375d8ec0 Mon Sep 17 00:00:00 2001 From: Siri Hansen Date: Fri, 6 Jul 2018 15:27:42 +0200 Subject: [kernel] Reduce risk of dead lock when terminating logger_sup --- lib/kernel/src/Makefile | 3 +- lib/kernel/src/error_logger.erl | 15 ++-- lib/kernel/src/kernel.app.src | 2 + lib/kernel/src/logger_disk_log_h.erl | 8 ++- lib/kernel/src/logger_h_common.erl | 13 ---- lib/kernel/src/logger_handler_watcher.erl | 113 ++++++++++++++++++++++++++++++ lib/kernel/src/logger_std_h.erl | 8 ++- lib/kernel/src/logger_sup.erl | 6 +- 8 files changed, 144 insertions(+), 24 deletions(-) create mode 100644 lib/kernel/src/logger_handler_watcher.erl diff --git a/lib/kernel/src/Makefile b/lib/kernel/src/Makefile index c595c25341..57f17defc8 100644 --- a/lib/kernel/src/Makefile +++ b/lib/kernel/src/Makefile @@ -112,7 +112,8 @@ MODULES = \ logger \ logger_backend \ logger_config \ - logger_std_h \ + logger_handler_watcher \ + logger_std_h \ logger_disk_log_h \ logger_h_common \ logger_filters \ diff --git a/lib/kernel/src/error_logger.erl b/lib/kernel/src/error_logger.erl index a7e7f19167..ad8c937882 100644 --- a/lib/kernel/src/error_logger.erl +++ b/lib/kernel/src/error_logger.erl @@ -74,8 +74,8 @@ start() -> type => worker, modules => dynamic}, case supervisor:start_child(logger_sup, ErrorLogger) of - {ok,_} -> - ok; + {ok,Pid} -> + ok = logger_handler_watcher:register_handler(?MODULE,Pid); Error -> Error end; @@ -95,9 +95,14 @@ start_link() -> %%% Stop the event manager -spec stop() -> ok. stop() -> - _ = supervisor:terminate_child(logger_sup,?MODULE), - _ = supervisor:delete_child(logger_sup,?MODULE), - ok. + case whereis(?MODULE) of + undefined -> + ok; + _Pid -> + _ = gen_event:stop(?MODULE,{shutdown,stopped},infinity), + _ = supervisor:delete_child(logger_sup,?MODULE), + ok + end. %%%----------------------------------------------------------------- %%% Callbacks for logger diff --git a/lib/kernel/src/kernel.app.src b/lib/kernel/src/kernel.app.src index 47dd7c03d5..4933eae76f 100644 --- a/lib/kernel/src/kernel.app.src +++ b/lib/kernel/src/kernel.app.src @@ -67,6 +67,7 @@ logger_filters, logger_formatter, logger_h_common, + logger_handler_watcher, logger_server, logger_simple_h, logger_std_h, @@ -129,6 +130,7 @@ kernel_refc, kernel_sup, logger, + logger_handler_watcher, logger_sup, net_kernel, net_sup, diff --git a/lib/kernel/src/logger_disk_log_h.erl b/lib/kernel/src/logger_disk_log_h.erl index 0a72654e11..e56531c3cb 100644 --- a/lib/kernel/src/logger_disk_log_h.erl +++ b/lib/kernel/src/logger_disk_log_h.erl @@ -488,7 +488,8 @@ start(Name, Config, HandlerState) -> type => worker, modules => [?MODULE]}, case supervisor:start_child(logger_sup, LoggerDLH) of - {ok,_Pid,Config1} -> + {ok,Pid,Config1} -> + ok = logger_handler_watcher:register_handler(Name,Pid), {ok,Config1}; Error -> Error @@ -506,8 +507,11 @@ stop(Name) -> %% system termination in order to avoid circular attempts %% at removing the handler (implying deadlocks and %% timeouts). + %% And we don't need to do supervisor:delete_child, since + %% the restart type is temporary, which means that the + %% child specification is automatically removed from the + %% supervisor when the process dies. _ = gen_server:call(Pid, stop), - _ = supervisor:delete_child(logger_sup, Name), ok end. diff --git a/lib/kernel/src/logger_h_common.erl b/lib/kernel/src/logger_h_common.erl index a40345dddc..854e5479b9 100644 --- a/lib/kernel/src/logger_h_common.erl +++ b/lib/kernel/src/logger_h_common.erl @@ -309,19 +309,6 @@ stop_or_restart(Name, {shutdown,Reason={overloaded,_Name,_QLen,_Mem}}, end, spawn(RemoveAndRestart), ok; - -stop_or_restart(Name, shutdown, _State) -> - %% Probably terminated by supervisor. Remove the handler to avoid - %% error printouts due to failing handler. - _ = case logger:get_handler_config(Name) of - {ok,_} -> - %% Spawning to avoid deadlock - spawn(logger,remove_handler,[Name]); - _ -> - ok - end, - ok; - stop_or_restart(_Name, _Reason, _State) -> ok. diff --git a/lib/kernel/src/logger_handler_watcher.erl b/lib/kernel/src/logger_handler_watcher.erl new file mode 100644 index 0000000000..b75c74c643 --- /dev/null +++ b/lib/kernel/src/logger_handler_watcher.erl @@ -0,0 +1,113 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2018. 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(logger_handler_watcher). + +-behaviour(gen_server). + +%% API +-export([start_link/0]). +-export([register_handler/2]). + +%% gen_server callbacks +-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2]). + +-define(SERVER, ?MODULE). + +-record(state, {handlers}). + +%%%=================================================================== +%%% API +%%%=================================================================== + +-spec start_link() -> {ok, Pid :: pid()} | + {error, Error :: {already_started, pid()}} | + {error, Error :: term()} | + ignore. +start_link() -> + gen_server:start_link({local, ?SERVER}, ?MODULE, [], []). + +-spec register_handler(Id::logger:handler_id(),Pid::pid()) -> ok. +register_handler(Id,Pid) -> + gen_server:call(?SERVER,{register,Id,Pid}). + +%%%=================================================================== +%%% gen_server callbacks +%%%=================================================================== + +-spec init(Args :: term()) -> {ok, State :: term()} | + {ok, State :: term(), Timeout :: timeout()} | + {ok, State :: term(), hibernate} | + {stop, Reason :: term()} | + ignore. +init([]) -> + process_flag(trap_exit, true), + {ok, #state{handlers=[]}}. + +-spec handle_call(Request :: term(), From :: {pid(), term()}, State :: term()) -> + {reply, Reply :: term(), NewState :: term()} | + {reply, Reply :: term(), NewState :: term(), Timeout :: timeout()} | + {reply, Reply :: term(), NewState :: term(), hibernate} | + {noreply, NewState :: term()} | + {noreply, NewState :: term(), Timeout :: timeout()} | + {noreply, NewState :: term(), hibernate} | + {stop, Reason :: term(), Reply :: term(), NewState :: term()} | + {stop, Reason :: term(), NewState :: term()}. +handle_call({register,Id,Pid}, _From, #state{handlers=Hs}=State) -> + Ref = erlang:monitor(process,Pid), + Hs1 = lists:keystore(Id,1,Hs,{Id,Ref}), + {reply, ok, State#state{handlers=Hs1}}. + +-spec handle_cast(Request :: term(), State :: term()) -> + {noreply, NewState :: term()} | + {noreply, NewState :: term(), Timeout :: timeout()} | + {noreply, NewState :: term(), hibernate} | + {stop, Reason :: term(), NewState :: term()}. +handle_cast(_Request, State) -> + {noreply, State}. + +-spec handle_info(Info :: timeout() | term(), State :: term()) -> + {noreply, NewState :: term()} | + {noreply, NewState :: term(), Timeout :: timeout()} | + {noreply, NewState :: term(), hibernate} | + {stop, Reason :: normal | term(), NewState :: term()}. +handle_info({'DOWN',Ref,process,_,shutdown}, #state{handlers=Hs}=State) -> + case lists:keytake(Ref,2,Hs) of + {value,{Id,Ref},Hs1} -> + %% Probably terminated by supervisor. Remove the handler to avoid + %% error printouts due to failing handler. + _ = case logger:get_handler_config(Id) of + {ok,_} -> + logger:remove_handler(Id); + _ -> + ok + end, + {noreply,State#state{handlers=Hs1}}; + false -> + {noreply, State} + end; +handle_info({'DOWN',Ref,process,_,_OtherReason}, #state{handlers=Hs}=State) -> + {noreply,State#state{handlers=lists:keydelete(Ref,2,Hs)}}; +handle_info(_Other,State) -> + {noreply,State}. + +-spec terminate(Reason :: normal | shutdown | {shutdown, term()} | term(), + State :: term()) -> any(). +terminate(_Reason, _State) -> + ok. diff --git a/lib/kernel/src/logger_std_h.erl b/lib/kernel/src/logger_std_h.erl index 480fafd6d8..9a2a1443b3 100644 --- a/lib/kernel/src/logger_std_h.erl +++ b/lib/kernel/src/logger_std_h.erl @@ -467,7 +467,8 @@ start(Name, Config, HandlerState) -> type => worker, modules => [?MODULE]}, case supervisor:start_child(logger_sup, LoggerStdH) of - {ok,_Pid,Config1} -> + {ok,Pid,Config1} -> + ok = logger_handler_watcher:register_handler(Name,Pid), {ok,Config1}; Error -> Error @@ -485,8 +486,11 @@ stop(Name) -> %% system termination in order to avoid circular attempts %% at removing the handler (implying deadlocks and %% timeouts). + %% And we don't need to do supervisor:delete_child, since + %% the restart type is temporary, which means that the + %% child specification is automatically removed from the + %% supervisor when the process dies. _ = gen_server:call(Pid, stop), - _ = supervisor:delete_child(logger_sup, Name), ok end. diff --git a/lib/kernel/src/logger_sup.erl b/lib/kernel/src/logger_sup.erl index dcdcdad0bd..3d6f482e20 100644 --- a/lib/kernel/src/logger_sup.erl +++ b/lib/kernel/src/logger_sup.erl @@ -46,7 +46,11 @@ init([]) -> intensity => 1, period => 5}, - {ok, {SupFlags, []}}. + Watcher = #{id => logger_handler_watcher, + start => {logger_handler_watcher, start_link, []}, + shutdown => brutal_kill}, + + {ok, {SupFlags, [Watcher]}}. %%%=================================================================== %%% Internal functions -- cgit v1.2.3