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_nif.c b/erts/emulator/beam/erl_nif.c
index af1acbfc90..4b4573d2f9 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -815,7 +815,7 @@ int enif_send(ErlNifEnv* env, const ErlNifPid* to_pid,
             }
 #endif
             if (have_seqtrace(stoken)) {
-                seq_trace_update_send(c_p);
+                seq_trace_update_serial(c_p);
                 seq_trace_output(stoken, msg, SEQ_TRACE_SEND,
                                  rp->common.id, c_p);
             }