Fix handle_no_resumed w/ multiple targets

handle_no_resumed is currently not considering multiple targets.

Say you have two inferiors 1 and 2, each connected to a different
target, A and B.

Now say you set inferior 2 running, with "continue &".

Now you select a thread of inferior 1, say thread 1.2, and continue in
the foreground.  All other threads of inferior 1 are left stopped.
Thread 1.2 exits, and thus target A has no other resumed thread, so it
reports TARGET_WAITKIND_NO_RESUMED.

At this point, if both inferiors were running in the same target,
handle_no_resumed would realize that threads of inferior 2 are still
executing, so the TARGET_WAITKIND_NO_RESUMED event should be ignored.
But because handle_no_resumed only walks the threads of the current
target, it misses noticing that threads of inferior 2 are still
executing.  The fix is just to walk over all threads of all targets.

A testcase covering the use case above will be added in a following
patch.  It can't be added yet because it depends on yet another fix to
handle_no_resumed not included here.

gdb/ChangeLog:

	PR gdb/26199
	* infrun.c (handle_no_resumed): Handle multiple targets.

2 files changed, 22 insertions, 5 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 09198ef..3fb80ab 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,6 +1,11 @@
 2020-07-10  Pedro Alves  <pedro@palves.net>
 
 	PR gdb/26199
+	* infrun.c (handle_no_resumed): Handle multiple targets.
+
+2020-07-10  Pedro Alves  <pedro@palves.net>
+
+	PR gdb/26199
 	* infrun.c (prepare_to_wait): Check target_can_async_p instead of
 	target_is_async_p.
 
diff --git a/gdb/infrun.c b/gdb/infrun.c
index a01e096..0f2f45a 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -5068,16 +5068,28 @@ handle_no_resumed (struct execution_control_state *ecs)
      have resumed threads _now_.  In the example above, this removes
      thread 3 from the thread list.  If thread 2 was re-resumed, we
      ignore this event.  If we find no thread resumed, then we cancel
-     the synchronous command show "no unwaited-for " to the user.  */
-  update_thread_list ();
+     the synchronous command and show "no unwaited-for " to the
+     user.  */
+
+  {
+    scoped_restore_current_thread restore_thread;
+
+    for (auto *target : all_non_exited_process_targets ())
+      {
+	switch_to_target_no_thread (target);
+	update_thread_list ();
+      }
+  }
 
-  for (thread_info *thread : all_non_exited_threads (ecs->target))
+  for (thread_info *thread : all_non_exited_threads ())
     {
       if (thread->executing
 	  || thread->suspend.waitstatus_pending_p)
 	{
-	  /* There were no unwaited-for children left in the target at
-	     some point, but there are now.  Just ignore.  */
+	  /* Either there were no unwaited-for children left in the
+	     target at some point, but there are now, or some target
+	     other than the eventing one has unwaited-for children
+	     left.  Just ignore.  */
 	  if (debug_infrun)
 	    fprintf_unfiltered (gdb_stdlog,
 				"infrun: TARGET_WAITKIND_NO_RESUMED "