Implement TARGET_WAITKIND_NO_RESUMED in the remote protocol

Testing with "maint set target-non-stop on" causes regressions in
tests that rely on TARGET_WAITKIND_NO_RESUMED, which isn't modelled on
the RSP.  In real all-stop, gdbserver detects the situation and
reporst error to GDB, and so the tests (e.g.,
gdb.threads/no-unwaited-for-left.exp) at fail quickly.  But with
"maint set target-non-stop on", GDB instead hangs forever waiting for
a stop reply that never comes, and so the tests take longer to time
out.

This adds a new "N" stop reply packet that maps 1-1 to
TARGET_WAITKIND_NO_RESUMED.

gdb/ChangeLog:
2015-11-30  Pedro Alves  <palves@redhat.com>

	PR 14618
	* NEWS (New remote packets): Mention the N stop reply.
	* remote.c (remote_protocol_features): Add "no-resumed" entry.
	(remote_query_supported): Report no-resumed+ support.
	(remote_parse_stop_reply): Handle 'N'.
	(process_stop_reply): Handle TARGET_WAITKIND_NO_RESUMED.
	(remote_wait_as): Handle 'N' / TARGET_WAITKIND_NO_RESUMED.
	(_initialize_remote): Register "set/show remote
	no-resumed-stop-reply" commands.

gdb/doc/ChangeLog:
2015-11-30  Pedro Alves  <palves@redhat.com>

	PR 14618
	* gdb.texinfo (Stop Reply Packets): Document the N stop reply.
	(Remote Configuration): Add the "set/show remote
	no-resumed-stop-reply" to the available settings table.
	(General Query Packets): Document the "no-resumed" qSupported
	feature.

gdb/gdbserver/ChangeLog:
2015-11-30  Pedro Alves  <palves@redhat.com>

	PR 14618
	* linux-low.c (linux_wait_1): If the last resumed thread is gone,
	report TARGET_WAITKIND_NO_RESUMED.
	* remote-utils.c (prepare_resume_reply): Handle
	TARGET_WAITKIND_NO_RESUMED.
	* server.c (report_no_resumed): New global.
	(handle_query) <qSupported>: Handle "no-resumed+".  Report
	"no-resumed+" support.
	(resume): When the target reports TARGET_WAITKIND_NO_RESUMED, only
	return error if the client doesn't support no-resumed events.
	(push_stop_notification): New function.
	(handle_target_event): Use it.  Report TARGET_WAITKIND_NO_RESUMED
	events if the client supports them.

gdb/testsuite/ChangeLog:
2015-11-30  Pedro Alves  <palves@redhat.com>

	* gdb.threads/no-unwaited-for-left.exp: Remove setup_kfail calls.

1 files changed, 32 insertions, 13 deletions

diff --git a/gdb/gdbserver/server.c b/gdb/gdbserver/server.c
index 0762f6a..18e9bf1 100644
--- a/gdb/gdbserver/server.c
+++ b/gdb/gdbserver/server.c
@@ -61,6 +61,10 @@ int report_fork_events;
 int report_vfork_events;
 int report_exec_events;
 int report_thread_events;
+
+/* Whether to report TARGET_WAITKING_NO_RESUMED events.  */
+static int report_no_resumed;
+
 int non_stop;
 int swbreak_feature;
 int hwbreak_feature;
@@ -2187,6 +2191,12 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
 		vCont_supported = 1;
 	      else if (strcmp (p, "QThreadEvents+") == 0)
 		;
+	      else if (strcmp (p, "no-resumed+") == 0)
+		{
+		  /* GDB supports and wants TARGET_WAITKIND_NO_RESUMED
+		     events.  */
+		  report_no_resumed = 1;
+		}
 	      else
 		{
 		  /* Move the unknown features all together.  */
@@ -2309,6 +2319,8 @@ handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
 
       strcat (own_buf, ";QThreadEvents+");
 
+      strcat (own_buf, ";no-resumed+");
+
       /* Reinitialize components as needed for the new connection.  */
       hostio_handle_new_gdb_connection ();
       target_handle_new_gdb_connection ();
@@ -2716,10 +2728,11 @@ resume (struct thread_resume *actions, size_t num_actions)
     {
       last_ptid = mywait (minus_one_ptid, &last_status, 0, 1);
 
-      if (last_status.kind == TARGET_WAITKIND_NO_RESUMED)
+      if (last_status.kind == TARGET_WAITKIND_NO_RESUMED
+	  && !report_no_resumed)
 	{
-	  /* No proper RSP support for this yet.  At least return
-	     error.  */
+	  /* The client does not support this stop reply.  At least
+	     return error.  */
 	  sprintf (own_buf, "E.No unwaited-for children left.");
 	  disable_async_io ();
 	  return;
@@ -4332,6 +4345,19 @@ handle_serial_event (int err, gdb_client_data client_data)
   return 0;
 }
 
+/* Push a stop notification on the notification queue.  */
+
+static void
+push_stop_notification (ptid_t ptid, struct target_waitstatus *status)
+{
+  struct vstop_notif *vstop_notif = XNEW (struct vstop_notif);
+
+  vstop_notif->status = *status;
+  vstop_notif->ptid = ptid;
+  /* Push Stop notification.  */
+  notif_push (&notif_stop, (struct notif_event *) vstop_notif);
+}
+
 /* Event-loop callback for target events.  */
 
 int
@@ -4345,7 +4371,8 @@ handle_target_event (int err, gdb_client_data client_data)
 
   if (last_status.kind == TARGET_WAITKIND_NO_RESUMED)
     {
-      /* No RSP support for this yet.  */
+      if (gdb_connected () && report_no_resumed)
+	push_stop_notification (null_ptid, &last_status);
     }
   else if (last_status.kind != TARGET_WAITKIND_IGNORE)
     {
@@ -4405,15 +4432,7 @@ handle_target_event (int err, gdb_client_data client_data)
 	    }
 	}
       else
-	{
-	  struct vstop_notif *vstop_notif = XNEW (struct vstop_notif);
-
-	  vstop_notif->status = last_status;
-	  vstop_notif->ptid = last_ptid;
-	  /* Push Stop notification.  */
-	  notif_push (&notif_stop,
-		      (struct notif_event *) vstop_notif);
-	}
+	push_stop_notification (last_ptid, &last_status);
     }
 
   /* Be sure to not change the selected thread behind GDB's back.