erts: Fix bug in seq_trace:set_token(label,_)

If internal seq-trace tuple is on old heap
an incorrect ref from old to new heap was made.

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/kernel/test/seq_trace_SUITE.erl b/lib/kernel/test/seq_trace_SUITE.erl
index ceb4e9cc49..7c1413287c 100644
--- a/lib/kernel/test/seq_trace_SUITE.erl
+++ b/lib/kernel/test/seq_trace_SUITE.erl
@@ -23,6 +23,7 @@
 	 init_per_group/2,end_per_group/2,
 	 init_per_testcase/2,end_per_testcase/2]).
 -export([token_set_get/1, tracer_set_get/1, print/1,
+         old_heap_token/1,
 	 send/1, distributed_send/1, recv/1, distributed_recv/1,
 	 trace_exit/1, distributed_exit/1, call/1, port/1,
 	 match_set_seq_token/1, gc_seq_token/1, label_capability_mismatch/1]).
@@ -46,6 +47,7 @@ suite() ->
 all() -> 
     [token_set_get, tracer_set_get, print, send,
      distributed_send, recv, distributed_recv, trace_exit,
+     old_heap_token,
      distributed_exit, call, port, match_set_seq_token,
      gc_seq_token, label_capability_mismatch].
 
@@ -531,6 +533,24 @@ get_port_message(Port) ->
     end.
 
 
+%% OTP-15849 ERL-700
+%% Verify changing label on existing token when it resides on old heap.
+%% Bug caused faulty ref from old to new heap.
+old_heap_token(Config) when is_list(Config) ->
+    seq_trace:set_token(label, 1),
+    erlang:garbage_collect(self(), [{type, minor}]),
+    erlang:garbage_collect(self(), [{type, minor}]),
+    %% Now token tuple should be on old-heap.
+    %% Set a new non-literal label which should reside on new-heap.
+    NewLabel = {self(), "new label"},
+    1 = seq_trace:set_token(label, NewLabel),
+
+    %% If bug, we now have a ref from old to new heap. Yet another minor gc
+    %% will make that a ref to deallocated memory.
+    erlang:garbage_collect(self(), [{type, minor}]),
+    {label,NewLabel} = seq_trace:get_token(label),
+    ok.
+
 
 match_set_seq_token(doc) ->
     ["Tests that match spec function set_seq_token does not "