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, 20 insertions, 3 deletions

diff --git a/gdb/remote.c b/gdb/remote.c
index 4daaf08c4b4..9d44ce1d7be 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1488,6 +1488,9 @@ enum {
   /* Support remote CTRL-C.  */
   PACKET_vCtrlC,
 
+  /* Support TARGET_WAITKIND_NO_RESUMED.  */
+  PACKET_no_resumed,
+
   PACKET_MAX
 };
 
@@ -4527,6 +4530,7 @@ static const struct protocol_feature remote_protocol_features[] = {
     PACKET_Qbtrace_conf_pt_size },
   { "vContSupported", PACKET_DISABLE, remote_supported_packet, PACKET_vContSupported },
   { "QThreadEvents", PACKET_DISABLE, remote_supported_packet, PACKET_QThreadEvents },
+  { "no-resumed", PACKET_DISABLE, remote_supported_packet, PACKET_no_resumed },
 };
 
 static char *remote_support_xml;
@@ -4622,6 +4626,9 @@ remote_query_supported (void)
       if (packet_set_cmd_state (PACKET_QThreadEvents) != AUTO_BOOLEAN_FALSE)
 	q = remote_query_supported_append (q, "QThreadEvents+");
 
+      if (packet_set_cmd_state (PACKET_no_resumed) != AUTO_BOOLEAN_FALSE)
+	q = remote_query_supported_append (q, "no-resumed+");
+
       /* Keep this one last to work around a gdbserver <= 7.10 bug in
 	 the qSupported:xmlRegisters=i386 handling.  */
       if (remote_support_xml != NULL)
@@ -6596,6 +6603,10 @@ Packet: '%s'\n"),
 	event->ptid = pid_to_ptid (pid);
       }
       break;
+    case 'N':
+      event->ws.kind = TARGET_WAITKIND_NO_RESUMED;
+      event->ptid = minus_one_ptid;
+      break;
     }
 
   if (target_is_non_stop_p () && ptid_equal (event->ptid, null_ptid))
@@ -6697,7 +6708,8 @@ process_stop_reply (struct stop_reply *stop_reply,
     ptid = inferior_ptid;
 
   if (status->kind != TARGET_WAITKIND_EXITED
-      && status->kind != TARGET_WAITKIND_SIGNALLED)
+      && status->kind != TARGET_WAITKIND_SIGNALLED
+      && status->kind != TARGET_WAITKIND_NO_RESUMED)
     {
       struct remote_state *rs = get_remote_state ();
       struct private_thread_info *remote_thr;
@@ -6875,7 +6887,7 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
       remote_fileio_request (buf, rs->ctrlc_pending_p);
       rs->ctrlc_pending_p = 0;
       break;
-    case 'T': case 'S': case 'X': case 'W':
+    case 'N': case 'T': case 'S': case 'X': case 'W':
       {
 	struct stop_reply *stop_reply;
 
@@ -6914,7 +6926,9 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
       break;
     }
 
-  if (status->kind == TARGET_WAITKIND_IGNORE)
+  if (status->kind == TARGET_WAITKIND_NO_RESUMED)
+    return minus_one_ptid;
+  else if (status->kind == TARGET_WAITKIND_IGNORE)
     {
       /* Nothing interesting happened.  If we're doing a non-blocking
 	 poll, we're done.  Otherwise, go back to waiting.  */
@@ -13755,6 +13769,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
   add_packet_config_cmd (&remote_protocol_packets[PACKET_QThreadEvents],
 			 "QThreadEvents", "thread-events", 0);
 
+  add_packet_config_cmd (&remote_protocol_packets[PACKET_no_resumed],
+			 "N stop reply", "no-resumed-stop-reply", 0);
+
   /* Assert that we've registered "set remote foo-packet" commands
      for all packet configs.  */
   {