Remote all-stop-on-top-of-non-stop

This is the first pass at implementing support for all-stop mode
running against the remote target using the non-stop variant of the
protocol.

The trickiest part here is the initial connection setup/synching.  We
need to fetch all inferiors' target descriptions etc. before stopping
threads, because stop_all_threads needs to read the threads' registers
(to record each thread's stop_pc).  But OTOH, the initial inferior
setup (target_post_attach, post_create_inferior, etc.), only works
correctly if the inferior is stopped...  So I've split that initial
setup part from attach_command_post_wait to a separate function, and
added a "still needs setup" flag to the inferior structure.  This is
similar to gdbserver/linux-low.c's handling of discovering the
process's target description).  Then if on connection all threads of
the remote inferior are running, when we go about stopping them, as
soon as they stop we call setup_inferior, from within
stop_all_threads.

Also, in all-stop, we need to process all the initial stop replies to
learn about all the pending signal the threads may already be stopped
for, and pick the one to report as current.  This is exposed by
gdb.threads/reconnect-signal.exp.

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

	* gdbthread.h (switch_to_thread_no_regs): Declare.
	* infcmd.c (setup_inferior): New function, factored out from ...
	(attach_command_post_wait): ... this.  Rename to ...
	(attach_post_wait): ... this.  Replace parameter async_exec with
	attach_post_wait_mode parameter.  Adjust.
	(enum attach_post_wait_mode): New enum.
	(struct attach_command_continuation_args): Replace 'async_exec'
	field with 'mode' field.
	(attach_command_continuation): Adjust.
	(attach_command): Add comment.  Mark the inferior as needing
	setup.  Adjust to use enum attach_post_wait_mode.
	(notice_new_inferior): Use switch_to_thread_no_regs.  Adjust to
	use enum attach_post_wait_mode.
	* inferior.h (setup_inferior): Declare.
	(struct inferior) <needs_setup>: New field.
	* infrun.c (set_last_target_status): Make extern.
	(stop_all_threads): Make extern.  Setup inferior, if necessary.
	* infrun.h (set_last_target_status, stop_all_threads): Declare.
	* remote-notif.c (remote_async_get_pending_events_handler)
	(handle_notification): Replace non_stop checks with
	target_is_non_stop_p() checks.
	* remote.c (remote_notice_new_inferior): Remove non_stop check.
	(remote_update_thread_list): Replace non_stop check with
	target_is_non_stop_p() check.
	(print_one_stopped_thread): New function.
	(process_initial_stop_replies): New 'from_tty' parameter.
	"Notice" all new live inferiors after storing initial stops as
	pending status in each corresponding thread.  If all-stop, stop
	all threads, try picking a signalled thread as current, and print
	the status of that one thread.  Record the last target status.
	(remote_start_remote): Replace non_stop checks with
	target_is_non_stop_p() checks.  Don't query for the remote current
	thread of use qOffsets here.  Pass from_tty to
	process_initial_stop_replies.
	(extended_remote_attach): Replace non_stop checks with
	target_is_non_stop_p() checks.
	(extended_remote_post_attach): Send qOffsets here.
	(remote_vcont_resume, remote_resume, remote_stop)
	(remote_interrupt, remote_parse_stop_reply, remote_wait): Replace
	non_stop checks with target_is_non_stop_p() checks.
	(remote_async): If target is non-stop, mark/clear the pending
	events token.
	* thread.c (switch_to_thread_no_regs): New function.

1 files changed, 57 insertions, 20 deletions

diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 54aa1ef..9aae860 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -2609,18 +2609,15 @@ proceed_after_attach (int pid)
   do_cleanups (old_chain);
 }
 
-/* attach_command --
-   takes a program started up outside of gdb and ``attaches'' to it.
-   This stops it cold in its tracks and allows us to start debugging it.
-   and wait for the trace-trap that results from attaching.  */
+/* See inferior.h.  */
 
-static void
-attach_command_post_wait (char *args, int from_tty, int async_exec)
+void
+setup_inferior (int from_tty)
 {
   struct inferior *inferior;
 
   inferior = current_inferior ();
-  inferior->control.stop_soon = NO_STOP_QUIETLY;
+  inferior->needs_setup = 0;
 
   /* If no exec file is yet known, try to determine it from the
      process itself.  */
@@ -2636,8 +2633,37 @@ attach_command_post_wait (char *args, int from_tty, int async_exec)
   target_post_attach (ptid_get_pid (inferior_ptid));
 
   post_create_inferior (&current_target, from_tty);
+}
+
+/* What to do after the first program stops after attaching.  */
+enum attach_post_wait_mode
+{
+  /* Do nothing.  Leaves threads as they are.  */
+  ATTACH_POST_WAIT_NOTHING,
+
+  /* Re-resume threads that are marked running.  */
+  ATTACH_POST_WAIT_RESUME,
+
+  /* Stop all threads.  */
+  ATTACH_POST_WAIT_STOP,
+};
+
+/* Called after we've attached to a process and we've seen it stop for
+   the first time.  If ASYNC_EXEC is true, re-resume threads that
+   should be running.  Else if ATTACH, */
+
+static void
+attach_post_wait (char *args, int from_tty, enum attach_post_wait_mode mode)
+{
+  struct inferior *inferior;
 
-  if (async_exec)
+  inferior = current_inferior ();
+  inferior->control.stop_soon = NO_STOP_QUIETLY;
+
+  if (inferior->needs_setup)
+    setup_inferior (from_tty);
+
+  if (mode == ATTACH_POST_WAIT_RESUME)
     {
       /* The user requested an `attach&', so be sure to leave threads
 	 that didn't get a signal running.  */
@@ -2657,7 +2683,7 @@ attach_command_post_wait (char *args, int from_tty, int async_exec)
 	    }
 	}
     }
-  else
+  else if (mode == ATTACH_POST_WAIT_STOP)
     {
       /* The user requested a plain `attach', so be sure to leave
 	 the inferior stopped.  */
@@ -2685,7 +2711,7 @@ struct attach_command_continuation_args
 {
   char *args;
   int from_tty;
-  int async_exec;
+  enum attach_post_wait_mode mode;
 };
 
 static void
@@ -2697,7 +2723,7 @@ attach_command_continuation (void *args, int err)
   if (err)
     return;
 
-  attach_command_post_wait (a->args, a->from_tty, a->async_exec);
+  attach_post_wait (a->args, a->from_tty, a->mode);
 }
 
 static void
@@ -2710,12 +2736,18 @@ attach_command_continuation_free_args (void *args)
   xfree (a);
 }
 
+/* "attach" command entry point.  Takes a program started up outside
+   of gdb and ``attaches'' to it.  This stops it cold in its tracks
+   and allows us to start debugging it.  */
+
 void
 attach_command (char *args, int from_tty)
 {
   int async_exec;
   struct cleanup *args_chain;
   struct target_ops *attach_target;
+  struct inferior *inferior = current_inferior ();
+  enum attach_post_wait_mode mode;
 
   dont_repeat ();		/* Not for the faint of heart */
 
@@ -2775,6 +2807,8 @@ attach_command (char *args, int from_tty)
   init_wait_for_inferior ();
   clear_proceed_status (0);
 
+  inferior->needs_setup = 1;
+
   if (target_is_non_stop_p ())
     {
       /* If we find that the current thread isn't stopped, explicitly
@@ -2790,12 +2824,13 @@ attach_command (char *args, int from_tty)
 	target_stop (pid_to_ptid (ptid_get_pid (inferior_ptid)));
     }
 
+  mode = async_exec ? ATTACH_POST_WAIT_RESUME : ATTACH_POST_WAIT_STOP;
+
   /* Some system don't generate traps when attaching to inferior.
      E.g. Mach 3 or GNU hurd.  */
   if (!target_attach_no_wait)
     {
       struct attach_command_continuation_args *a;
-      struct inferior *inferior = current_inferior ();
 
       /* Careful here.  See comments in inferior.h.  Basically some
 	 OSes don't ignore SIGSTOPs on continue requests anymore.  We
@@ -2808,7 +2843,7 @@ attach_command (char *args, int from_tty)
       a = XNEW (struct attach_command_continuation_args);
       a->args = xstrdup (args);
       a->from_tty = from_tty;
-      a->async_exec = async_exec;
+      a->mode = mode;
       add_inferior_continuation (attach_command_continuation, a,
 				 attach_command_continuation_free_args);
       /* Done with ARGS.  */
@@ -2822,7 +2857,7 @@ attach_command (char *args, int from_tty)
   /* Done with ARGS.  */
   do_cleanups (args_chain);
 
-  attach_command_post_wait (args, from_tty, async_exec);
+  attach_post_wait (args, from_tty, mode);
 }
 
 /* We had just found out that the target was already attached to an
@@ -2837,7 +2872,7 @@ void
 notice_new_inferior (ptid_t ptid, int leave_running, int from_tty)
 {
   struct cleanup* old_chain;
-  int async_exec;
+  enum attach_post_wait_mode mode;
 
   old_chain = make_cleanup (null_cleanup, NULL);
 
@@ -2845,12 +2880,14 @@ notice_new_inferior (ptid_t ptid, int leave_running, int from_tty)
      they're stopped for some reason other than us telling it to, the
      target reports a signal != GDB_SIGNAL_0.  We don't try to
      resume threads with such a stop signal.  */
-  async_exec = non_stop;
+  mode = non_stop ? ATTACH_POST_WAIT_RESUME : ATTACH_POST_WAIT_NOTHING;
 
   if (!ptid_equal (inferior_ptid, null_ptid))
     make_cleanup_restore_current_thread ();
 
-  switch_to_thread (ptid);
+  /* Avoid reading registers -- we haven't fetched the target
+     description yet.  */
+  switch_to_thread_no_regs (find_thread_ptid (ptid));
 
   /* When we "notice" a new inferior we need to do all the things we
      would normally do if we had just attached to it.  */
@@ -2871,7 +2908,7 @@ notice_new_inferior (ptid_t ptid, int leave_running, int from_tty)
       a = XNEW (struct attach_command_continuation_args);
       a->args = xstrdup ("");
       a->from_tty = from_tty;
-      a->async_exec = async_exec;
+      a->mode = mode;
       add_inferior_continuation (attach_command_continuation, a,
 				 attach_command_continuation_free_args);
 
@@ -2879,8 +2916,8 @@ notice_new_inferior (ptid_t ptid, int leave_running, int from_tty)
       return;
     }
 
-  async_exec = leave_running;
-  attach_command_post_wait ("" /* args */, from_tty, async_exec);
+  mode = leave_running ? ATTACH_POST_WAIT_RESUME : ATTACH_POST_WAIT_NOTHING;
+  attach_post_wait ("" /* args */, from_tty, mode);
 
   do_cleanups (old_chain);
 }