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Diffstat (limited to 'erts/preloaded/src/erts_code_purger.erl')
| -rw-r--r-- | erts/preloaded/src/erts_code_purger.erl | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/erts/preloaded/src/erts_code_purger.erl b/erts/preloaded/src/erts_code_purger.erl new file mode 100644 index 0000000000..fd214228c7 --- /dev/null +++ b/erts/preloaded/src/erts_code_purger.erl @@ -0,0 +1,377 @@ +%% +%% %CopyrightBegin% +%% +%% Copyright Ericsson AB 2016. 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(erts_code_purger). + +%% Purpose : Implement system process erts_code_purger +%% to handle code module purging. + +-export([start/0, purge/1, soft_purge/1, pending_purge_lambda/3, + finish_after_on_load/2]). + +-spec start() -> term(). +start() -> + register(erts_code_purger, self()), + process_flag(trap_exit, true), + wait_for_request(). + +wait_for_request() -> + handle_request(receive Msg -> Msg end, []). + +handle_request({purge, Mod, From, Ref}, Reqs) when is_atom(Mod), is_pid(From) -> + {Res, NewReqs} = do_purge(Mod, Reqs), + From ! {reply, purge, Res, Ref}, + check_requests(NewReqs); +handle_request({soft_purge, Mod, From, Ref}, Reqs) when is_atom(Mod), is_pid(From) -> + {Res, NewReqs} = do_soft_purge(Mod, Reqs), + From ! {reply, soft_purge, Res, Ref}, + check_requests(NewReqs); +handle_request({finish_after_on_load, {Mod,Keep}, From, Ref}, Reqs) + when is_atom(Mod), is_boolean(Keep), is_pid(From) -> + NewReqs = do_finish_after_on_load(Mod, Keep, Reqs), + From ! {reply, finish_after_on_load, ok, Ref}, + check_requests(NewReqs); +handle_request({test_purge, Mod, From, Type, Ref}, Reqs) when is_atom(Mod), is_pid(From) -> + NewReqs = do_test_purge(Mod, From, Type, Ref, Reqs), + check_requests(NewReqs); +handle_request(_Garbage, Reqs) -> + check_requests(Reqs). + +check_requests([]) -> + wait_for_request(); +check_requests([R|Rs]) -> + handle_request(R, Rs). + +%% +%% Processes that tries to call a fun that belongs to +%% a module that currently is being purged will end +%% up here (pending_purge_lambda) in a suspended state. +%% When the purge operation completes or aborts (soft +%% purge that failed) these processes will be resumed. +%% +pending_purge_lambda(_Module, Fun, Args) -> + %% + %% When the process is resumed, the following + %% scenarios exist: + %% * The code that the fun refers to is still + %% there due to a failed soft purge. The + %% call to the fun will succeed via apply/2. + %% * The code was purged, and a current version + %% of the module is loaded which does not + %% contain this fun. The call will result + %% in an exception being raised. + %% * The code was purged, and no current + %% version of the module is loaded. An attempt + %% to load the module (via the error_handler) + %% will be made. This may or may not succeed. + %% If the module is loaded, it may or may + %% not contain the fun. The call will + %% succeed if the error_handler was able + %% to load the module and loaded module + %% contains this fun; otherwise, an exception + %% will be raised. + %% + apply(Fun, Args). + +%% purge(Module) +%% Kill all processes running code from *old* Module, and then purge the +%% module. Return {WasOld, DidKill}: +%% {false, false} there was no old module to purge +%% {true, false} module purged, no process killed +%% {true, true} module purged, at least one process killed + +purge(Mod) when is_atom(Mod) -> + Ref = make_ref(), + erts_code_purger ! {purge, Mod, self(), Ref}, + receive + {reply, purge, Result, Ref} -> + Result + end. + +do_purge(Mod, Reqs) -> + case erts_internal:purge_module(Mod, prepare) of + false -> + {{false, false}, Reqs}; + true -> + {DidKill, NewReqs} = check_proc_code(erlang:processes(), + Mod, true, Reqs), + true = erts_internal:purge_module(Mod, complete), + {{true, DidKill}, NewReqs} + end. + +%% soft_purge(Module) +%% Purge old code only if no procs remain that run old code. +%% Return true in that case, false if procs remain (in this +%% case old code is not purged) + +soft_purge(Mod) -> + Ref = make_ref(), + erts_code_purger ! {soft_purge, Mod, self(), Ref}, + receive + {reply, soft_purge, Result, Ref} -> + Result + end. + +do_soft_purge(Mod, Reqs) -> + case erts_internal:purge_module(Mod, prepare) of + false -> + {true, Reqs}; + true -> + {PurgeOp, NewReqs} = check_proc_code(erlang:processes(), + Mod, false, Reqs), + {erts_internal:purge_module(Mod, PurgeOp), NewReqs} + end. + +%% finish_after_on_load(Module, Keep) +%% Finish after running on_load function. If Keep is false, +%% purge the code for the on_load function. + +finish_after_on_load(Mod, Keep) -> + Ref = make_ref(), + erts_code_purger ! {finish_after_on_load, {Mod,Keep}, self(), Ref}, + receive + {reply, finish_after_on_load, Result, Ref} -> + Result + end. + +do_finish_after_on_load(Mod, Keep, Reqs) -> + erlang:finish_after_on_load(Mod, Keep), + case Keep of + true -> + Reqs; + false -> + case erts_internal:purge_module(Mod, prepare_on_load) of + false -> + Reqs; + true -> + {_DidKill, NewReqs} = + check_proc_code(erlang:processes(), + Mod, true, Reqs), + true = erts_internal:purge_module(Mod, complete), + NewReqs + end + end. + + +%% +%% check_proc_code(Pids, Mod, Hard, Preqs) - Send asynchronous +%% requests to all processes to perform a check_process_code +%% operation. Each process will check their own state and +%% reply with the result. If 'Hard' equals +%% - true, processes that refer 'Mod' will be killed. If +%% any processes were killed true is returned; otherwise, +%% false. +%% - false, and any processes refer 'Mod', 'abort' will +%% be returned; otherwise, 'complete'. +%% +%% We only allow ?MAX_CPC_NO_OUTSTANDING_KILLS +%% outstanding kills. This both in order to avoid flooding +%% our message queue with 'DOWN' messages and limiting the +%% amount of memory used to keep references to all +%% outstanding kills. +%% + +-define(MAX_CPC_NO_OUTSTANDING_KILLS, 10). + +-record(cpc_static, {hard, module, tag, purge_requests}). + +-record(cpc_kill, {outstanding = [], + no_outstanding = 0, + waiting = [], + killed = false}). + +check_proc_code(Pids, Mod, Hard, PReqs) -> + Tag = erlang:make_ref(), + CpcS = #cpc_static{hard = Hard, + module = Mod, + tag = Tag, + purge_requests = PReqs}, + cpc_receive(CpcS, cpc_init(CpcS, Pids, 0), #cpc_kill{}, []). + +cpc_receive(#cpc_static{hard = true} = CpcS, + 0, + #cpc_kill{outstanding = [], waiting = [], killed = Killed}, + PReqs) -> + %% No outstanding cpc requests. We did a hard check, so result is + %% whether or not we killed any processes... + cpc_result(CpcS, PReqs, Killed); +cpc_receive(#cpc_static{hard = false} = CpcS, 0, _KillState, PReqs) -> + %% No outstanding cpc requests and we did a soft check that succeeded... + cpc_result(CpcS, PReqs, complete); +cpc_receive(#cpc_static{tag = Tag} = CpcS, NoReq, KillState0, PReqs) -> + receive + {check_process_code, {Tag, _Pid}, false} -> + %% Process not referring the module; done with this process... + cpc_receive(CpcS, NoReq-1, KillState0, PReqs); + {check_process_code, {Tag, Pid}, true} -> + %% Process referring the module... + case CpcS#cpc_static.hard of + false -> + %% ... and soft check. The whole operation failed so + %% no point continuing; fail straight away. Garbage + %% messages from this session will be ignored + %% by following sessions... + cpc_result(CpcS, PReqs, abort); + true -> + %% ... and hard check; schedule kill of it... + KillState1 = cpc_sched_kill(Pid, KillState0), + cpc_receive(CpcS, NoReq-1, KillState1, PReqs) + end; + {'DOWN', MonRef, process, _, _} -> + KillState1 = cpc_handle_down(MonRef, KillState0), + cpc_receive(CpcS, NoReq, KillState1, PReqs); + PReq when element(1, PReq) == purge; + element(1, PReq) == soft_purge; + element(1, PReq) == test_purge -> + %% A new purge request; save it until later... + cpc_receive(CpcS, NoReq, KillState0, [PReq | PReqs]); + _Garbage -> + %% Garbage message; ignore it... + cpc_receive(CpcS, NoReq, KillState0, PReqs) + end. + +cpc_result(#cpc_static{purge_requests = PReqs}, NewPReqs, Res) -> + {Res, PReqs ++ cpc_reverse(NewPReqs)}. + +cpc_reverse([_] = L) -> L; +cpc_reverse(Xs) -> cpc_reverse(Xs, []). + +cpc_reverse([], Ys) -> Ys; +cpc_reverse([X|Xs], Ys) -> cpc_reverse(Xs, [X|Ys]). + +cpc_handle_down(R, #cpc_kill{outstanding = Rs, + no_outstanding = N} = KillState0) -> + try + NewOutst = cpc_list_rm(R, Rs), + KillState1 = KillState0#cpc_kill{outstanding = NewOutst, + no_outstanding = N-1}, + cpc_sched_kill_waiting(KillState1) + catch + throw : undefined -> %% Triggered by garbage message... + KillState0 + end. + +cpc_list_rm(_R, []) -> + throw(undefined); +cpc_list_rm(R, [R|Rs]) -> + Rs; +cpc_list_rm(R0, [R1|Rs]) -> + [R1|cpc_list_rm(R0, Rs)]. + +cpc_sched_kill_waiting(#cpc_kill{waiting = []} = KillState) -> + KillState; +cpc_sched_kill_waiting(#cpc_kill{outstanding = Rs, + no_outstanding = N, + waiting = [P|Ps]} = KillState) -> + R = erlang:monitor(process, P), + exit(P, kill), + KillState#cpc_kill{outstanding = [R|Rs], + no_outstanding = N+1, + waiting = Ps, + killed = true}. + +cpc_sched_kill(Pid, #cpc_kill{no_outstanding = N, waiting = Pids} = KillState) + when N >= ?MAX_CPC_NO_OUTSTANDING_KILLS -> + KillState#cpc_kill{waiting = [Pid|Pids]}; +cpc_sched_kill(Pid, + #cpc_kill{outstanding = Rs, no_outstanding = N} = KillState) -> + R = erlang:monitor(process, Pid), + exit(Pid, kill), + KillState#cpc_kill{outstanding = [R|Rs], + no_outstanding = N+1, + killed = true}. + +cpc_request(#cpc_static{tag = Tag, module = Mod}, Pid) -> + erts_internal:check_process_code(Pid, Mod, [{async, {Tag, Pid}}]). + +cpc_init(_CpcS, [], NoReqs) -> + NoReqs; +cpc_init(CpcS, [Pid|Pids], NoReqs) -> + cpc_request(CpcS, Pid), + cpc_init(CpcS, Pids, NoReqs+1). + +% end of check_proc_code() implementation. + +%% +%% FOR TESTING ONLY +%% +%% do_test_purge() is for testing only. The purge is done +%% as usual, but the tester can control when to enter the +%% specific phases. +%% +do_test_purge(Mod, From, true, Ref, Reqs) -> + {Res, NewReqs} = do_test_hard_purge(Mod, From, Ref, Reqs), + From ! {test_purge, Res, Ref}, + NewReqs; +do_test_purge(Mod, From, false, Ref, Reqs) -> + {Res, NewReqs} = do_test_soft_purge(Mod, From, Ref, Reqs), + From ! {test_purge, Res, Ref}, + NewReqs; +do_test_purge(_, _, _, _, Reqs) -> + Reqs. + +do_test_soft_purge(Mod, From, Ref, Reqs) -> + PrepRes = erts_internal:purge_module(Mod, prepare), + TestRes = test_progress(started, From, Ref, ok), + case PrepRes of + false -> + _ = test_progress(continued, From, Ref, TestRes), + {true, Reqs}; + true -> + {PurgeOp, NewReqs} = check_proc_code(erlang:processes(), + Mod, false, Reqs), + _ = test_progress(continued, From, Ref, TestRes), + {erts_internal:purge_module(Mod, PurgeOp), NewReqs} + end. + +do_test_hard_purge(Mod, From, Ref, Reqs) -> + PrepRes = erts_internal:purge_module(Mod, prepare), + TestRes = test_progress(started, From, Ref, ok), + case PrepRes of + false -> + _ = test_progress(continued, From, Ref, TestRes), + {{false, false}, Reqs}; + true -> + {DidKill, NewReqs} = check_proc_code(erlang:processes(), + Mod, true, Reqs), + _ = test_progress(continued, From, Ref, TestRes), + true = erts_internal:purge_module(Mod, complete), + {{true, DidKill}, NewReqs} + end. + +test_progress(_State, _From, _Ref, died) -> + %% Test process died; continue so we wont + %% leave the system in an inconsistent + %% state... + died; +test_progress(started, From, Ref, ok) -> + From ! {started, Ref}, + Mon = erlang:monitor(process, From), + receive + {'DOWN', Mon, process, From, _} -> died; + {continue, Ref} -> erlang:demonitor(Mon, [flush]), ok + end; +test_progress(continued, From, Ref, ok) -> + From ! {continued, Ref}, + Mon = erlang:monitor(process, From), + receive + {'DOWN', Mon, process, From, _} -> died; + {complete, Ref} -> erlang:demonitor(Mon, [flush]), ok + end. + |