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Diffstat (limited to 'erts/preloaded/src/erts_code_purger.erl')
| -rw-r--r-- | erts/preloaded/src/erts_code_purger.erl | 299 |
1 files changed, 299 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..a64860bec8 --- /dev/null +++ b/erts/preloaded/src/erts_code_purger.erl @@ -0,0 +1,299 @@ +%% +%% %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]). + +-spec start() -> term(). +start() -> + register(erts_code_purger, self()), + process_flag(trap_exit, true), + loop(). + +loop() -> + receive + {purge,Mod,From,Ref} when is_atom(Mod), is_pid(From) -> + Res = do_purge(Mod), + From ! {reply, purge, Res, Ref}; + + {soft_purge,Mod,From,Ref} when is_atom(Mod), is_pid(From) -> + Res = do_soft_purge(Mod), + From ! {reply, soft_purge, Res, Ref}; + + _Other -> ignore + end, + loop(). + + +%% 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) -> + case erts_internal:copy_literals(Mod, true) of + false -> + {false, false}; + true -> + DidKill = check_proc_code(erlang:processes(), Mod, true), + true = erts_internal:copy_literals(Mod, false), + WasPurged = erts_internal:purge_module(Mod), + {WasPurged, DidKill} + 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) -> + case erts_internal:copy_literals(Mod, true) of + false -> + true; + true -> + DoPurge = check_proc_code(erlang:processes(), Mod, false), + true = erts_internal:copy_literals(Mod, false), + case DoPurge of + false -> + false; + true -> + erts_internal:purge_module(Mod), + true + end + end. + +%% +%% check_proc_code(Pids, Mod, Hard) - 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', false will +%% returned; otherwise, true. +%% +%% Requests will be sent to all processes identified by +%% Pids at once, but without allowing GC to be performed. +%% Check process code operations that are aborted due to +%% GC need, will be restarted allowing GC. However, only +%% ?MAX_CPC_GC_PROCS outstanding operation allowing GC at +%% a time will be allowed. This in order not to blow up +%% memory wise. +%% +%% We also 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. +%% + +%% We maybe should allow more than two outstanding +%% GC requests, but for now we play it safe... +-define(MAX_CPC_GC_PROCS, 2). +-define(MAX_CPC_NO_OUTSTANDING_KILLS, 10). + +-record(cpc_static, {hard, module, tag}). + +-record(cpc_kill, {outstanding = [], + no_outstanding = 0, + waiting = [], + killed = false}). + +check_proc_code(Pids, Mod, Hard) -> + Tag = erlang:make_ref(), + CpcS = #cpc_static{hard = Hard, + module = Mod, + tag = Tag}, + check_proc_code(CpcS, cpc_init(CpcS, Pids, 0), 0, [], #cpc_kill{}, true). + +check_proc_code(#cpc_static{hard = true}, 0, 0, [], + #cpc_kill{outstanding = [], waiting = [], killed = Killed}, + true) -> + %% No outstanding requests. We did a hard check, so result is whether or + %% not we killed any processes... + Killed; +check_proc_code(#cpc_static{hard = false}, 0, 0, [], _KillState, Success) -> + %% No outstanding requests and we did a soft check... + Success; +check_proc_code(#cpc_static{hard = false, tag = Tag} = CpcS, NoReq0, NoGcReq0, + [], _KillState, false) -> + %% Failed soft check; just cleanup the remaining replies corresponding + %% to the requests we've sent... + {NoReq1, NoGcReq1} = receive + {check_process_code, {Tag, _P, GC}, _Res} -> + case GC of + false -> {NoReq0-1, NoGcReq0}; + true -> {NoReq0, NoGcReq0-1} + end + end, + check_proc_code(CpcS, NoReq1, NoGcReq1, [], _KillState, false); +check_proc_code(#cpc_static{tag = Tag} = CpcS, NoReq0, NoGcReq0, NeedGC0, + KillState0, Success) -> + + %% Check if we should request a GC operation + {NoGcReq1, NeedGC1} = case NoGcReq0 < ?MAX_CPC_GC_PROCS of + GcOpAllowed when GcOpAllowed == false; + NeedGC0 == [] -> + {NoGcReq0, NeedGC0}; + _ -> + {NoGcReq0+1, cpc_request_gc(CpcS,NeedGC0)} + end, + + %% Wait for a cpc reply or 'DOWN' message + {NoReq1, NoGcReq2, Pid, Result, KillState1} = cpc_recv(Tag, + NoReq0, + NoGcReq1, + KillState0), + + %% Check the result of the reply + case Result of + aborted -> + %% Operation aborted due to the need to GC in order to + %% determine if the process is referring the module. + %% Schedule the operation for restart allowing GC... + check_proc_code(CpcS, NoReq1, NoGcReq2, [Pid|NeedGC1], KillState1, + Success); + false -> + %% Process not referring the module; done with this process... + check_proc_code(CpcS, NoReq1, NoGcReq2, NeedGC1, KillState1, + Success); + true -> + %% Process referring the module... + case CpcS#cpc_static.hard of + false -> + %% ... and soft check. The whole operation failed so + %% no point continuing; clean up and fail... + check_proc_code(CpcS, NoReq1, NoGcReq2, [], KillState1, + false); + true -> + %% ... and hard check; schedule kill of it... + check_proc_code(CpcS, NoReq1, NoGcReq2, NeedGC1, + cpc_sched_kill(Pid, KillState1), Success) + end; + 'DOWN' -> + %% Handled 'DOWN' message + check_proc_code(CpcS, NoReq1, NoGcReq2, NeedGC1, + KillState1, Success) + end. + +cpc_recv(Tag, NoReq, NoGcReq, #cpc_kill{outstanding = []} = KillState) -> + receive + {check_process_code, {Tag, Pid, GC}, Res} -> + cpc_handle_cpc(NoReq, NoGcReq, GC, Pid, Res, KillState) + end; +cpc_recv(Tag, NoReq, NoGcReq, + #cpc_kill{outstanding = [R0, R1, R2, R3, R4 | _]} = KillState) -> + receive + {'DOWN', R, process, _, _} when R == R0; + R == R1; + R == R2; + R == R3; + R == R4 -> + cpc_handle_down(NoReq, NoGcReq, R, KillState); + {check_process_code, {Tag, Pid, GC}, Res} -> + cpc_handle_cpc(NoReq, NoGcReq, GC, Pid, Res, KillState) + end; +cpc_recv(Tag, NoReq, NoGcReq, #cpc_kill{outstanding = [R|_]} = KillState) -> + receive + {'DOWN', R, process, _, _} -> + cpc_handle_down(NoReq, NoGcReq, R, KillState); + {check_process_code, {Tag, Pid, GC}, Res} -> + cpc_handle_cpc(NoReq, NoGcReq, GC, Pid, Res, KillState) + end. + +cpc_handle_down(NoReq, NoGcReq, R, #cpc_kill{outstanding = Rs, + no_outstanding = N} = KillState) -> + {NoReq, NoGcReq, undefined, 'DOWN', + cpc_sched_kill_waiting(KillState#cpc_kill{outstanding = cpc_list_rm(R, Rs), + no_outstanding = N-1})}. + +cpc_list_rm(R, [R|Rs]) -> + Rs; +cpc_list_rm(R0, [R1|Rs]) -> + [R1|cpc_list_rm(R0, Rs)]. + +cpc_handle_cpc(NoReq, NoGcReq, false, Pid, Res, KillState) -> + {NoReq-1, NoGcReq, Pid, Res, KillState}; +cpc_handle_cpc(NoReq, NoGcReq, true, Pid, Res, KillState) -> + {NoReq, NoGcReq-1, Pid, Res, KillState}. + +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, AllowGc) -> + erts_internal:check_process_code(Pid, Mod, [{async, {Tag, Pid, AllowGc}}, + {allow_gc, AllowGc}, + {copy_literals, true}]). + +cpc_request_gc(CpcS, [Pid|Pids]) -> + cpc_request(CpcS, Pid, true), + Pids. + +cpc_init(_CpcS, [], NoReqs) -> + NoReqs; +cpc_init(CpcS, [Pid|Pids], NoReqs) -> + cpc_request(CpcS, Pid, false), + cpc_init(CpcS, Pids, NoReqs+1). + +% end of check_proc_code() implementation. |