erts: Move reason in dist messages to payload

The dist messages EXIT, EXIT2 and MONITOR_DOWN have been
updated with new versions that send the reason term as
part of the payload of the message instead of as part
of the control message.

This allows the decode of the reason to be done by the
receiving process instead of the dist entry which in turn
makes it possible for multiple decodes to be done in
parallel.

This change is done in order to make it easier to fragment
the potentially large payload of EXIT, EXIT2 and MONITOR_DOWN
into multiple distribution messages.

OTP-15611

1 files changed, 66 insertions, 3 deletions

diff --git a/erts/emulator/beam/erl_proc_sig_queue.h b/erts/emulator/beam/erl_proc_sig_queue.h
index 5a02708bb7..39cee6f230 100644
--- a/erts/emulator/beam/erl_proc_sig_queue.h
+++ b/erts/emulator/beam/erl_proc_sig_queue.h
@@ -89,6 +89,7 @@
 #endif
 
 struct erl_mesg;
+struct erl_dist_external;
 
 typedef struct {
     struct erl_mesg *next;
@@ -212,6 +213,34 @@ erts_proc_sig_send_exit(Process *c_p, Eterm from, Eterm to,
 
 /**
  *
+ * @brief Send an exit signal to a process.
+ *
+ * This function is used instead of erts_proc_sig_send_link_exit()
+ * when the signal arrives via the distribution and
+ * therefore no link structure is available.
+ *
+ * @param[in]     dep           Distribution entry of channel
+ *                              that the signal arrived on.
+ *
+ * @param[in]     from          Identifier of sender.
+ *
+ * @param[in]     to            Identifier of receiver.
+ *
+ * @param[in]     dist_ext      The exit reason in external term format
+ *
+ * @param[in]     reason        Exit reason.
+ *
+ * @param[in]     token         Seq trace token.
+ *
+ */
+void
+erts_proc_sig_send_dist_exit(DistEntry *dep,
+                             Eterm from, Eterm to,
+                             ErtsDistExternal *dist_ext,
+                             Eterm reason, Eterm token);
+
+/**
+ *
  * @brief Send an exit signal due to broken link to a process.
  *
  *
@@ -282,7 +311,7 @@ erts_proc_sig_send_unlink(Process *c_p, ErtsLink *lnk);
  *
  * This function is used instead of erts_proc_sig_send_link_exit()
  * when the signal arrives via the distribution and
- * no link structure is available.
+ * therefore no link structure is available.
  *
  * @param[in]     dep           Distribution entry of channel
  *                              that the signal arrived on.
@@ -291,6 +320,8 @@ erts_proc_sig_send_unlink(Process *c_p, ErtsLink *lnk);
  *
  * @param[in]     to            Identifier of receiver.
  *
+ * @param[in]     dist_ext      The exit reason in external term format
+ *
  * @param[in]     reason        Exit reason.
  *
  * @param[in]     token         Seq trace token.
@@ -299,6 +330,7 @@ erts_proc_sig_send_unlink(Process *c_p, ErtsLink *lnk);
 void
 erts_proc_sig_send_dist_link_exit(struct dist_entry_ *dep,
                                   Eterm from, Eterm to,
+                                  ErtsDistExternal *dist_ext,
                                   Eterm reason, Eterm token);
 
 /**
@@ -307,7 +339,7 @@ erts_proc_sig_send_dist_link_exit(struct dist_entry_ *dep,
  *
  * This function is used instead of erts_proc_sig_send_unlink()
  * when the signal arrives via the distribution and
- * no link structure is available.
+ * therefore no link structure is available.
  *
  * @param[in]     dep           Distribution entry of channel
  *                              that the signal arrived on.
@@ -380,7 +412,7 @@ erts_proc_sig_send_monitor(ErtsMonitor *mon, Eterm to);
  *
  * This function is used instead of erts_proc_sig_send_monitor_down()
  * when the signal arrives via the distribution and
- * no link structure is available.
+ * therefore no monitor structure is available.
  *
  * @param[in]     dep           Pointer to distribution entry
  *                              of channel that the signal
@@ -392,12 +424,15 @@ erts_proc_sig_send_monitor(ErtsMonitor *mon, Eterm to);
  *
  * @param[in]     to            Identifier of receiver.
  *
+ * @param[in]     dist_ext      The exit reason in external term format
+ *
  * @param[in]     reason        Exit reason.
  *
  */
 void
 erts_proc_sig_send_dist_monitor_down(DistEntry *dep, Eterm ref,
                                      Eterm from, Eterm to,
+                                     ErtsDistExternal *dist_ext,
                                      Eterm reason);
 
 /**
@@ -962,6 +997,34 @@ void
 erts_proc_sig_handle_pending_suspend(Process *c_p);
 
 /**
+ *
+ * @brief Decode the reason term in an external signal
+ *
+ * Any distributed signal with a payload only has the control
+ * message decoded by the dist entry. The final decode of the
+ * payload is done by the process when it inspects the signal
+ * by calling this function.
+ *
+ * This functions handles both messages and link/monitor exits.
+ *
+ * Return true if the decode was successful, false otherwise.
+ *
+ * @param[in]   c_p             Pointer to executing process
+ *
+ * @param[in]   proc_lock       Locks held by process. Should always be MAIN.
+ *
+ * @param[in]   msgp            The signal to decode
+ *
+ * @param[in]   force_off_heap  If the term should be forced to be off-heap
+ */
+int
+erts_proc_sig_decode_dist(Process *proc, ErtsProcLocks proc_locks,
+                          ErtsMessage *msgp, int force_off_heap);
+
+ErtsDistExternal *
+erts_proc_sig_get_external(ErtsMessage *msgp);
+
+/**
  * @brief Initialize this functionality
  */
 void erts_proc_sig_queue_init(void);