Exited threads.

* thread.c (enum thread_state): New.
	(thread_state main_thread_running): Delete, in favor of...
	(thread_state main_thread_state): ... this.  Update throughout.
	(clear_thread_inferior_resources): New, split from free_thread.
	(free_thread): Call clear_thread_inferior_resources.
	(init_thread_list): Set main thread to stopped state.
	(add_thread_silent): Take care of PTID reuses.
	(delete_thread): If deleting inferior_ptid or a thread with
	refcount > 0, mark it as exited, but still keep it in the list.
	Only notify of thread exits, if we haven't done so yet.
	(iterate_over_threads): Make it safe to delete threads while
	iterating over them.
	(do_captured_list_thread_ids): Don't account for exited threads.
	(thread_alive): Check for the THREAD_EXITED state, and don't set
	ptid to -1 on exited threads.
	(set_running): Update to account for extra possible states.
	(is_thread_state): New.
	(is_stopped, is_exited): New.
	(is_running): Implement in terms of is_thread_state.
	(any_running): Update.
	(print_thread_info): Update.  Account for exited threads.  Don't
	warn about missed frame restoring here, its done in the cleanup.
	(switch_to_thread): Don't read from a thread that has gone.
	(restore_current_thread): In non-stop mode, do a full context
	switch.
	(restore_selected_frame): Add a frame_level argument.  Rewrite.
	(struct current_thread_cleanup): Add selected_frame_level and
	was_stopped members.
	(do_restore_current_thread_cleanup): Check if thread was stopped
	and still is, and if the target has registers, stack and memory
	before restoring the selected frame.  Don't delete the cleanup
	argument here.
	(restore_current_thread_cleanup_dtor): New.
	(make_cleanup_restore_current_thread): Remove all arguments.
	Rewrite.
	(thread_apply_all_command): Update.  Prune threads.
	(thread_apply_command): Update.
	(thread_command): Account for currently selected exited thread.
	(do_captured_thread_select): Check for a running thread.  Prune
	threads.
	(_initialize_thread): Make "info threads", "thread", "thread
	apply", and "thread apply all" appliable without a selected thread.
	* gdbthread.h (struct thread_info): Replace running_ by state_.
	Add refcount.
	(is_exited, is_stopped): Declare.
	(make_cleanup_restore_current_thread): Remove all arguments.
	* infrun.c: Include "event-top.h".
	(fetch_inferior_event): In non-stop mode, restore selected thread
	and frame after handling the event and running breakpoint
	commands.  Display GDB prompt if needed.
	(normal_stop): In non-stop mode, don't print thread switching
	notice.
	* cli/cli-decode.c (set_cmd_no_selected_thread_ok)
	(get_cmd_no_selected_thread_ok): New.
	* cli/cli-decode.h (CMD_NO_SELECTED_THREAD_OK): New.
	(set_cmd_no_selected_thread_ok, get_cmd_no_selected_thread_ok):
	Declare.
	* cli/cli-cmds.c: Set "pwd", "help", "info", "show" as
	no-selected-thread ok.
	* top.c (execute_command): Check for non no-selected-thread-ok
	commands.
	* linux-nat.c (struct saved_ptids, threads_to_delete)
	(record_dead_thread, prune_lwps): Delete.
	(exit_lwp): Unconditionally delete thread.
	(linux_nat_resume): Remove prune_lwps call.
	* infcmd.c (proceed_thread_callback): Check if !is_stopped instead
	of is_running.  Adjust to make_cleanup_restore_current_thread
	interface change.
	* mi/mi-main.c (mi_cmd_execute): Only allow a few commands if the
	selected thread has exited.
	* inf-loop.c (inferior_event_handler): Don't display the prompt
	here.
	* varobj.c (c_value_of_root): Update.
	* defs.h (make_cleanup_dtor): Declare.
	* utils.c (make_cleanup_dtor): New.

	* Makefile.in (infrun.o): Depend on $(event_top_h).

gdb/infrun.c

@@ -48,6 +48,7 @@
 
 #include "gdb_assert.h"
 #include "mi/mi-common.h"
+#include "event-top.h"
 
 /* Prototypes for local functions */
 
@@ -1530,11 +1531,20 @@ fetch_inferior_event (void *client_data)
 {
   struct execution_control_state ecss;
   struct execution_control_state *ecs = &ecss;
+  struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
+  int was_sync = sync_execution;
 
   memset (ecs, 0, sizeof (*ecs));
 
   overlay_cache_invalid = 1;
 
+  if (non_stop)
+    /* In non-stop mode, the user/frontend should not notice a thread
+       switch due to internal events.  Make sure we reverse to the
+       user selected thread and frame after handling the event and
+       running any breakpoint commands.  */
+    make_cleanup_restore_current_thread ();
+
   /* We have to invalidate the registers BEFORE calling target_wait
      because they can be loaded from the target while in target_wait.
      This makes remote debugging a bit more efficient for those
@@ -1571,6 +1581,14 @@ fetch_inferior_event (void *client_data)
       else
 	inferior_event_handler (INF_EXEC_COMPLETE, NULL);
     }
+
+  /* Revert thread and frame.  */
+  do_cleanups (old_chain);
+
+  /* If the inferior was in sync execution mode, and now isn't,
+     restore the prompt.  */
+  if (was_sync && !sync_execution)
+    display_gdb_prompt (0);
 }
 
 /* Prepare an execution control state for looping through a
@@ -3709,6 +3727,11 @@ normal_stop (void)
 
   get_last_target_status (&last_ptid, &last);
 
+  /* In non-stop mode, we don't want GDB to switch threads behind the
+     user's back, to avoid races where the user is typing a command to
+     apply to thread x, but GDB switches to thread y before the user
+     finishes entering the command.  */
+
   /* As with the notification of thread events, we want to delay
      notifying the user that we've switched thread context until
      the inferior actually stops.
@@ -3716,7 +3739,8 @@ normal_stop (void)
      There's no point in saying anything if the inferior has exited.
      Note that SIGNALLED here means "exited with a signal", not
      "received a signal".  */
-  if (!ptid_equal (previous_inferior_ptid, inferior_ptid)
+  if (!non_stop
+      && !ptid_equal (previous_inferior_ptid, inferior_ptid)
       && target_has_execution
       && last.kind != TARGET_WAITKIND_SIGNALLED
       && last.kind != TARGET_WAITKIND_EXITED)