seq_trace: Inherit trace token on spawn

Trace tokens can be lost when a process delegates message sending
to a child process, which is pretty surprising and limits the
usefulness of seq tracing. One example of this is gen_statem:call/4
which uses a child process to implement timeouts without the risk
of a late message arriving to the caller.

This commit attempts to remedy this by propagating the trace token
to spawned processes, and adds optional tracing for process
spawning as well.

1 files changed, 1 insertions, 1 deletions

diff --git a/erts/emulator/beam/erl_proc_sig_queue.c b/erts/emulator/beam/erl_proc_sig_queue.c
index 9c74a2c355..877a139d85 100644
--- a/erts/emulator/beam/erl_proc_sig_queue.c
+++ b/erts/emulator/beam/erl_proc_sig_queue.c
@@ -994,7 +994,7 @@ send_gen_exit_signal(Process *c_p, Eterm from_tag,
 
     seq_trace = c_p && have_seqtrace(token);
     if (seq_trace)
-        seq_trace_update_send(c_p);
+        seq_trace_update_serial(c_p);
 
 #ifdef USE_VM_PROBES
     utag_sz = 0;