gdbserver: Queue no-resumed event after thread exit

Normally, if the last resumed thread on the target exits, the server
sends a no-resumed event to GDB.  If however, GDB enables the
GDB_THREAD_OPTION_EXIT option on a thread, and, that thread exits, the
server sends a thread exit event for that thread instead.

In all-stop RSP mode, since events can only be forwarded to GDB one at
a time, and the whole target stops whenever an event is reported, GDB
resumes the target again after getting a THREAD_EXITED event, and then
the server finally reports back a no-resumed event if/when
appropriate.

For non-stop RSP though, events are asynchronous, and if the server
sends a thread-exit event for the last resumed thread, the no-resumed
event is never sent.  This patch makes sure that in non-stop mode, the
server queues a no-resumed event after the thread-exit event if it was
the last resumed thread that exited.

Without this, we'd see failures in step-over-thread-exit testcases
added later in the series, like so:

   continue
   Continuing.
 - No unwaited-for children left.
 - (gdb) PASS: gdb.threads/step-over-thread-exit.exp: displaced-stepping=off: non-stop=on: target-non-stop=on: schedlock=off: ns_stop_all=1: continue stops when thread exits
 + FAIL: gdb.threads/step-over-thread-exit.exp: displaced-stepping=off: non-stop=on: target-non-stop=on: schedlock=off: ns_stop_all=1: continue stops when thread exits (timeout)

(and other similar ones)

Reviewed-By: Andrew Burgess <aburgess@redhat.com>
Change-Id: I927d78b30f88236dbd5634b051a716f72420e7c7

gdbserver/linux-low.cc

@@ -2972,7 +2972,6 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
   int report_to_gdb;
   int trace_event;
   int in_step_range;
-  int any_resumed;
 
   threads_debug_printf ("[%s]", target_pid_to_str (ptid).c_str ());
 
@@ -2986,23 +2985,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
   in_step_range = 0;
   ourstatus->set_ignore ();
 
-  auto status_pending_p_any = [&] (thread_info *thread)
+  bool was_any_resumed = any_resumed ();
-    {
-      return status_pending_p_callback (thread, minus_one_ptid);
-    };
-
-  auto not_stopped = [&] (thread_info *thread)
-    {
-      return not_stopped_callback (thread, minus_one_ptid);
-    };
-
-  /* Find a resumed LWP, if any.  */
-  if (find_thread (status_pending_p_any) != NULL)
-    any_resumed = 1;
-  else if (find_thread (not_stopped) != NULL)
-    any_resumed = 1;
-  else
-    any_resumed = 0;
 
   if (step_over_bkpt == null_ptid)
     pid = wait_for_event (ptid, &w, options);
@@ -3013,7 +2996,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
       pid = wait_for_event (step_over_bkpt, &w, options & ~WNOHANG);
     }
 
-  if (pid == 0 || (pid == -1 && !any_resumed))
+  if (pid == 0 || (pid == -1 && !was_any_resumed))
     {
       gdb_assert (target_options & TARGET_WNOHANG);
 
@@ -6177,6 +6160,32 @@ linux_process_target::thread_stopped (thread_info *thread)
   return get_thread_lwp (thread)->stopped;
 }
 
+bool
+linux_process_target::any_resumed ()
+{
+  bool any_resumed;
+
+  auto status_pending_p_any = [&] (thread_info *thread)
+    {
+      return status_pending_p_callback (thread, minus_one_ptid);
+    };
+
+  auto not_stopped = [&] (thread_info *thread)
+    {
+      return not_stopped_callback (thread, minus_one_ptid);
+    };
+
+  /* Find a resumed LWP, if any.  */
+  if (find_thread (status_pending_p_any) != NULL)
+    any_resumed = 1;
+  else if (find_thread (not_stopped) != NULL)
+    any_resumed = 1;
+  else
+    any_resumed = 0;
+
+  return any_resumed;
+}
+
 /* This exposes stop-all-threads functionality to other modules.  */
 
 void

gdbserver/linux-low.h

@@ -259,6 +259,8 @@ public:
 
   bool thread_stopped (thread_info *thread) override;
 
+  bool any_resumed () override;
+
   void pause_all (bool freeze) override;
 
   void unpause_all (bool unfreeze) override;

gdbserver/server.cc

@@ -4731,7 +4731,17 @@ handle_target_event (int err, gdb_client_data client_data)
 	    }
 	}
       else
-	push_stop_notification (cs.last_ptid, cs.last_status);
+	{
+	  push_stop_notification (cs.last_ptid, cs.last_status);
+
+	  if (cs.last_status.kind () == TARGET_WAITKIND_THREAD_EXITED
+	      && !target_any_resumed ())
+	    {
+	      target_waitstatus ws;
+	      ws.set_no_resumed ();
+	      push_stop_notification (null_ptid, ws);
+	    }
+	}
     }
 
   /* Be sure to not change the selected thread behind GDB's back.

gdbserver/target.cc

@@ -614,6 +614,12 @@ process_stratum_target::thread_stopped (thread_info *thread)
   gdb_assert_not_reached ("target op thread_stopped not supported");
 }
 
+bool
+process_stratum_target::any_resumed ()
+{
+  return true;
+}
+
 bool
 process_stratum_target::supports_get_tib_address ()
 {

gdbserver/target.h

@@ -319,6 +319,9 @@ public:
   /* Return true if THREAD is known to be stopped now.  */
   virtual bool thread_stopped (thread_info *thread);
 
+  /* Return true if any thread is known to be resumed.  */
+  virtual bool any_resumed ();
+
   /* Return true if the get_tib_address op is supported.  */
   virtual bool supports_get_tib_address ();
 
@@ -683,6 +686,9 @@ target_read_btrace_conf (struct btrace_target_info *tinfo,
 #define target_supports_software_single_step() \
   the_target->supports_software_single_step ()
 
+#define target_any_resumed() \
+  the_target->any_resumed ()
+
 ptid_t mywait (ptid_t ptid, struct target_waitstatus *ourstatus,
 	       target_wait_flags options, int connected_wait);