PROTON-2818: clearer code and comments.

c/src/proactor/epoll.c

@@ -1123,7 +1123,7 @@ static void write_flush(pconnection_t *pc) {
 
 static void pconnection_connected_lh(pconnection_t *pc);
 static void pconnection_maybe_connect_lh(pconnection_t *pc);
-static void pconnection_first_connect_lh(pconnection_t *pc);
+static bool pconnection_first_connect_lh(pconnection_t *pc);
 
 static pn_event_batch_t *pconnection_process(pconnection_t *pc, uint32_t events, bool sched_ready, bool topup) {
   bool waking = false;
@@ -1142,14 +1142,10 @@ static pn_event_batch_t *pconnection_process(pconnection_t *pc, uint32_t events,
   if (sched_ready) schedule_done(&pc->task);
 
   if (pc->first_schedule) {
-    // Normal case: resumed logic from pn_proactor_connect2.
-    // But possible tie: pn_connection_wake() or pn_proactor_disconnect().
-    // Respect the latter.  Check former after connect attempt.
     pc->first_schedule = false;
     assert(!topup && !events);
     if (!pc->queued_disconnect) {
-      pconnection_first_connect_lh(pc);  // Drops and reaquires lock.  Wake or disconnect state may change.
-      if (pc->psocket.epoll_io.fd != -1 && !pc->queued_disconnect && !pni_task_wake_pending(&pc->task)) {
+      if (pconnection_first_connect_lh(pc)) {
         unlock(&pc->task.mutex);
         return NULL;
       }
@@ -1435,7 +1431,8 @@ bool schedule_if_inactive(pn_proactor_t *p) {
 }
 
 // Call from pconnection_process with task lock held.
-static void pconnection_first_connect_lh(pconnection_t *pc) {
+// Return true if the socket is connecting and there are no Proton events to deliver.
+static bool pconnection_first_connect_lh(pconnection_t *pc) {
   unlock(&pc->task.mutex);
   // TODO: move this step to a separate worker thread that scales in response to multiple blocking DNS lookups.
   int gai_error = pgetaddrinfo(pc->host, pc->port, 0, &pc->addrinfo);
@@ -1444,9 +1441,12 @@ static void pconnection_first_connect_lh(pconnection_t *pc) {
   if (!gai_error) {
     pc->ai = pc->addrinfo;
     pconnection_maybe_connect_lh(pc); /* Start connection attempts */
+    if (pc->psocket.epoll_io.fd != -1 && !pc->queued_disconnect && !pni_task_wake_pending(&pc->task))
+      return true;
   } else {
     psocket_gai_error(&pc->psocket, gai_error, "connect to ");
   }
+  return false;
 }
 
 void pn_proactor_connect2(pn_proactor_t *p, pn_connection_t *c, pn_transport_t *t, const char *addr) {

c/src/proactor/epoll_raw_connection.c

@@ -183,23 +183,28 @@ pn_raw_connection_t *pn_raw_connection(void) {
 }
 
 // Call from pconnection_process with task lock held.
-static void praw_connection_first_connect_lh(praw_connection_t *prc) {
+// Return true if the socket is connecting and there are no Proton events to deliver.
+static bool praw_connection_first_connect_lh(praw_connection_t *prc) {
   const char *host;
   const char *port;
 
   unlock(&prc->task.mutex);
   size_t addrlen = strlen(prc->taddr);
   char *addr_buf = (char*) alloca(addrlen+1);
   pni_parse_addr(prc->taddr, addr_buf, addrlen+1, &host, &port);
+  // TODO: move this step to a separate worker thread that scales in response to multiple blocking DNS lookups.
   int gai_error = pgetaddrinfo(host, port, 0, &prc->addrinfo);
   lock(&prc->task.mutex);
 
   if (!gai_error) {
     prc->ai = prc->addrinfo;
     praw_connection_maybe_connect_lh(prc); /* Start connection attempts */
+    if (prc->psocket.epoll_io.fd != -1 && !pni_task_wake_pending(&prc->task))
+      return true;
   } else {
     psocket_gai_error(prc, gai_error, "connect to ", prc->taddr);
   }
+  return false;
 }
 
 void pn_proactor_raw_connect(pn_proactor_t *p, pn_raw_connection_t *rc, const char *addr) {
@@ -403,6 +408,16 @@ pn_event_batch_t *pni_raw_connection_process(task_t *t, uint32_t io_events, bool
   }
   int events = io_events;
   int fd = rc->psocket.epoll_io.fd;
+
+  if (rc->first_schedule) {
+    rc->first_schedule = false;
+    assert(!events); // No socket yet.
+    assert(!rc->connected);
+    if (praw_connection_first_connect_lh(rc)) {
+      unlock(&rc->task.mutex);
+      return NULL;
+    }
+  }
   if (!rc->connected) {
     if (events & (EPOLLHUP | EPOLLERR)) {
       praw_connection_maybe_connect_lh(rc);
@@ -422,18 +437,6 @@ pn_event_batch_t *pni_raw_connection_process(task_t *t, uint32_t io_events, bool
     }
     if (events & EPOLLOUT)
       praw_connection_connected_lh(rc);
-    if (rc->first_schedule) {
-      // Normal case: resumed logic from pn_proactor_raw_connect.
-      // But possible tie: pn_raw_connection_wake()
-      // Defer wake check until getaddrinfo is done.
-      rc->first_schedule = false;
-      assert(!events); // No socket yet.
-      praw_connection_first_connect_lh(rc);  // Drops and reacquires lock.
-      if (rc->psocket.epoll_io.fd != -1 && !pni_task_wake_pending(&rc->task)) {
-        unlock(&rc->task.mutex);
-        return NULL;
-      }
-    }
 
     unlock(&rc->task.mutex);
     return &rc->batch;