From 9f1d9a497ba42df8c122bc1ac2c1add6f64a164c Mon Sep 17 00:00:00 2001 From: Mikael Pettersson Date: Sat, 10 Mar 2018 16:19:26 +0100 Subject: make erlang:process_info/1 not retrieve messages process_info/1 retrieves a number of properties related to a process, including the list of messages in its mailbox. This is potentially unsafe if the target process has a large number of queued messages: - there is no a priori upper bound on the amount of memory being allocated to hold that list, and - the loop to retrieve the messages is uninterruptible, so the Erlang scheduler where this executes blocks for the duration We've seen process_info/1 bring down heavily loaded nodes on more than one occasion. At least once it appeared to have blocked the Erlang heart process from executing, causing the external heart to kill the VM. Consequently this removes 'messages' from the list of process_info tags to retrieve for process_info/1. Note that process_info/1 still retrieves 'message_queue_len', and process_info/2 can still retrieve 'messages' when asked to. A few places in the OTP libraries need minor adjustments, since they want 'message_queue_len' but compute it from the length of the list of messages. --- erts/emulator/beam/erl_bif_info.c | 1 - lib/common_test/src/test_server_ctrl.erl | 2 +- lib/dialyzer/test/r9c_SUITE_data/src/mnesia/mnesia_tm.erl | 2 +- lib/mnesia/src/mnesia_tm.erl | 2 +- lib/stdlib/src/c.erl | 4 ++-- 5 files changed, 5 insertions(+), 6 deletions(-) diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c index 4050fb6146..c5f498c3b1 100644 --- a/erts/emulator/beam/erl_bif_info.c +++ b/erts/emulator/beam/erl_bif_info.c @@ -717,7 +717,6 @@ static Eterm pi_1_keys[] = { am_initial_call, am_status, am_message_queue_len, - am_messages, am_links, am_dictionary, am_trap_exit, diff --git a/lib/common_test/src/test_server_ctrl.erl b/lib/common_test/src/test_server_ctrl.erl index 8ef28b3343..8d9b2d2913 100644 --- a/lib/common_test/src/test_server_ctrl.erl +++ b/lib/common_test/src/test_server_ctrl.erl @@ -5164,7 +5164,7 @@ display_info([Pid|T], R, M) -> Other end, Reds = fetch(reductions, Info), - LM = length(fetch(messages, Info)), + LM = fetch(message_queue_len, Info), pformat(io_lib:format("~w", [Pid]), io_lib:format("~tw", [Call]), io_lib:format("~tw", [Curr]), Reds, LM), diff --git a/lib/dialyzer/test/r9c_SUITE_data/src/mnesia/mnesia_tm.erl b/lib/dialyzer/test/r9c_SUITE_data/src/mnesia/mnesia_tm.erl index 09e310530d..af49ceff72 100644 --- a/lib/dialyzer/test/r9c_SUITE_data/src/mnesia/mnesia_tm.erl +++ b/lib/dialyzer/test/r9c_SUITE_data/src/mnesia/mnesia_tm.erl @@ -2051,7 +2051,7 @@ display_pid_info(Pid) -> Other end, Reds = fetch(reductions, Info), - LM = length(fetch(messages, Info)), + LM = fetch(message_queue_len, Info), pformat(io_lib:format("~p", [Pid]), io_lib:format("~p", [Call]), io_lib:format("~p", [Curr]), Reds, LM) diff --git a/lib/mnesia/src/mnesia_tm.erl b/lib/mnesia/src/mnesia_tm.erl index ebf580d09e..a586b86760 100644 --- a/lib/mnesia/src/mnesia_tm.erl +++ b/lib/mnesia/src/mnesia_tm.erl @@ -2212,7 +2212,7 @@ display_pid_info(Pid) -> Other end, Reds = fetch(reductions, Info), - LM = length(fetch(messages, Info)), + LM = fetch(message_queue_len, Info), pformat(io_lib:format("~p", [Pid]), io_lib:format("~tp", [Call]), io_lib:format("~tp", [Curr]), Reds, LM) diff --git a/lib/stdlib/src/c.erl b/lib/stdlib/src/c.erl index c04a201ce1..cc08295480 100644 --- a/lib/stdlib/src/c.erl +++ b/lib/stdlib/src/c.erl @@ -564,7 +564,7 @@ display_info(Pid) -> Other end, Reds = fetch(reductions, Info), - LM = length(fetch(messages, Info)), + LM = fetch(message_queue_len, Info), HS = fetch(heap_size, Info), SS = fetch(stack_size, Info), iformat(w(Pid), mfa_string(Call), @@ -882,7 +882,7 @@ portinfo(Id) -> procline(Name, Info, Pid) -> Call = initial_call(Info), Reds = fetch(reductions, Info), - LM = length(fetch(messages, Info)), + LM = fetch(message_queue_len, Info), procformat(io_lib:format("~tw",[Name]), io_lib:format("~w",[Pid]), io_lib:format("~ts",[mfa_string(Call)]), -- cgit v1.2.3 From f78c3ee64cd1328a03e4680d893ebfe8e47ac8b4 Mon Sep 17 00:00:00 2001 From: Mikael Pettersson Date: Sat, 10 Mar 2018 17:03:03 +0100 Subject: update erlang:process_info/1 docs --- erts/doc/src/erlang.xml | 1 - 1 file changed, 1 deletion(-) diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index 3ed0f59b7d..08c55d595c 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -4881,7 +4881,6 @@ RealSystem = system + MissedSystem initial_call status message_queue_len - messages links dictionary trap_exit -- cgit v1.2.3