aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorSverker Eriksson <[email protected]>2019-03-28 19:32:52 +0100
committerSverker Eriksson <[email protected]>2019-03-28 22:17:42 +0100
commit2c8e6848d3b1d13529e83d8cf76e0a2a458fea52 (patch)
tree62ff19f3d7b6203d5e03d3844b51448930cc4249
parentbff3ef4e41c7637b0a9c1ca5a42a1c28efe242f5 (diff)
downloadotp-2c8e6848d3b1d13529e83d8cf76e0a2a458fea52.tar.gz
otp-2c8e6848d3b1d13529e83d8cf76e0a2a458fea52.tar.bz2
otp-2c8e6848d3b1d13529e83d8cf76e0a2a458fea52.zip
erts: Fix bug in process_info(reductions)
returning incorrect result as * current process might not be RUNNING in which case REDS_IN is actually used as def_arg_reg[5] * FCALLS might not have been swapped out * the SAVED_CALLS case was wrong and returned number of reds left
-rw-r--r--erts/emulator/beam/beam_emu.c15
-rw-r--r--erts/emulator/beam/msg_instrs.tab1
-rw-r--r--erts/emulator/test/process_SUITE.erl42
3 files changed, 52 insertions, 6 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index e909a0b4da..ce986fdd7a 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -3231,20 +3231,23 @@ erts_is_builtin(Eterm Mod, Eterm Name, int arity)
/*
- * Return the current number of reductions for the given process.
+ * Return the current number of reductions consumed by the given process.
* To get the total number of reductions, p->reds must be added.
*/
Uint
-erts_current_reductions(Process *current, Process *p)
+erts_current_reductions(Process *c_p, Process *p)
{
- if (current != p) {
+ Sint reds_left;
+ if (c_p != p || !(erts_atomic32_read_nob(&c_p->state)
+ & ERTS_PSFLG_RUNNING)) {
return 0;
- } else if (current->fcalls < 0 && ERTS_PROC_GET_SAVED_CALLS_BUF(current)) {
- return current->fcalls + CONTEXT_REDS;
+ } else if (c_p->fcalls < 0 && ERTS_PROC_GET_SAVED_CALLS_BUF(c_p)) {
+ reds_left = c_p->fcalls + CONTEXT_REDS;
} else {
- return REDS_IN(current) - current->fcalls;
+ reds_left = c_p->fcalls;
}
+ return REDS_IN(c_p) - reds_left;
}
int
diff --git a/erts/emulator/beam/msg_instrs.tab b/erts/emulator/beam/msg_instrs.tab
index 9bf3aefaca..a6a0dec451 100644
--- a/erts/emulator/beam/msg_instrs.tab
+++ b/erts/emulator/beam/msg_instrs.tab
@@ -105,6 +105,7 @@ i_loop_rec(Dest) {
$SET_CP_I_ABS(I);
c_p->arity = 0;
c_p->current = NULL;
+ c_p->fcalls = FCALLS;
FCALLS -= erts_proc_sig_receive_helper(c_p, FCALLS, neg_o_reds,
&msgp, &get_out);
SWAPIN;
diff --git a/erts/emulator/test/process_SUITE.erl b/erts/emulator/test/process_SUITE.erl
index 57eb082d64..545dd95bef 100644
--- a/erts/emulator/test/process_SUITE.erl
+++ b/erts/emulator/test/process_SUITE.erl
@@ -44,6 +44,7 @@
process_info_garbage_collection/1,
process_info_smoke_all/1,
process_info_status_handled_signal/1,
+ process_info_reductions/1,
bump_reductions/1, low_prio/1, binary_owner/1, yield/1, yield2/1,
otp_4725/1, bad_register/1, garbage_collect/1, otp_6237/1,
process_info_messages/1, process_flag_badarg/1, process_flag_heap_size/1,
@@ -84,6 +85,7 @@ all() ->
process_info_garbage_collection,
process_info_smoke_all,
process_info_status_handled_signal,
+ process_info_reductions,
bump_reductions, low_prio, yield, yield2, otp_4725,
bad_register, garbage_collect, process_info_messages,
process_flag_badarg, process_flag_heap_size,
@@ -1084,6 +1086,46 @@ process_info_status_handled_signal(Config) when is_list(Config) ->
false = erlang:is_process_alive(P),
ok.
+%% OTP-15709
+%% Provoke a bug where process_info(reductions) returned wrong result
+%% because REDS_IN (def_arg_reg[5]) is read when the process in not running.
+process_info_reductions(Config) when is_list(Config) ->
+ pi_reductions_tester(spawn_link(fun() -> pi_reductions_spinnloop() end)),
+ pi_reductions_tester(spawn_link(fun() -> pi_reductions_recvloop() end)),
+ ok.
+
+pi_reductions_tester(Pid) ->
+ {_, DiffList} =
+ lists:foldl(fun(_, {Prev, Acc}) ->
+ %% Add another item that force sending the request
+ %% as a signal, like 'current_function'.
+ PI = process_info(Pid, [reductions, current_function]),
+ [{reductions,Reds}, {current_function,_}] = PI,
+ Diff = Reds - Prev,
+ {Diff, true} = {Diff, (Diff >= 0)},
+ {Diff, true} = {Diff, (Diff =< 1000*1000)},
+ {Reds, [Diff | Acc]}
+ end,
+ {0, []},
+ lists:seq(1,10)),
+ unlink(Pid),
+ exit(Pid,kill),
+ io:format("Reduction diffs: ~p\n", [DiffList]),
+ ok.
+
+pi_reductions_spinnloop() ->
+ %% 6 args to make use of def_arg_reg[5] which is also used as REDS_IN
+ pi_reductions_spinnloop(1, atom, "hej", self(), make_ref(), 3.14).
+
+pi_reductions_spinnloop(A,B,C,D,E,F) ->
+ pi_reductions_spinnloop(B,C,D,E,F,A).
+
+pi_reductions_recvloop() ->
+ receive
+ "a free lunch" -> false
+ end.
+
+
%% Tests erlang:bump_reductions/1.
bump_reductions(Config) when is_list(Config) ->
erlang:garbage_collect(),