Merge async and sync code paths some more

This patch makes the execution control code use largely the same
mechanisms in both sync- and async-capable targets.  This means using
continuations and use the event loop to react to target events on sync
targets as well.  The trick is to immediately mark infrun's event loop
source after resume instead of calling wait_for_inferior.  Then
fetch_inferior_event is adjusted to do a blocking wait on sync
targets.

Tested on x86_64 Fedora 20, native and gdbserver, with and without
"maint set target-async off".

gdb/ChangeLog:
2015-09-09  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (bpstat_do_actions_1, until_break_command): Don't
	check whether the target can async.
	* inf-loop.c (inferior_event_handler): Only call target_async if
	the target can async.
	* infcall.c: Include top.h and interps.h.
	(run_inferior_call): For the interpreter to sync mode while
	running the infcall.  Call wait_sync_command_done instead of
	wait_for_inferior plus normal_stop.
	* infcmd.c (prepare_execution_command): Don't check whether the
	target can async when running in the foreground.
	(step_1): Delete synchronous case handling.
	(step_once): Always install a continuation, even in sync mode.
	(until_next_command, finish_forward): Don't check whether the
	target can async.
	(attach_command_post_wait, notice_new_inferior): Always install a
	continuation, even in sync mode.
	* infrun.c (mark_infrun_async_event_handler): New function.
	(proceed): In sync mode, mark infrun's event source instead of
	waiting for events here.
	(fetch_inferior_event): If the target can't async, do a blocking
	wait.
	(prepare_to_wait): In sync mode, mark infrun's event source.
	(infrun_async_inferior_event_handler): No longer bail out if the
	target can't async.
	* infrun.h (mark_infrun_async_event_handler): New declaration.
	* linux-nat.c (linux_nat_wait_1): Remove calls to
	set_sigint_trap/clear_sigint_trap.
	(linux_nat_terminal_inferior): No longer check whether the target
	can async.
	* mi/mi-interp.c (mi_on_sync_execution_done): Update and simplify
	comment.
	(mi_execute_command_input_handler): No longer check whether the
	target is async.  Update and simplify comment.
	* target.c (default_target_wait): New function.
	* target.h (struct target_ops) <to_wait>: Now defaults to
	default_target_wait.
	(default_target_wait): Declare.
	* top.c (wait_sync_command_done): New function, factored out from
	...
	(maybe_wait_sync_command_done): ... this.
	* top.h (wait_sync_command_done): Declare.
	* target-delegates.c: Regenerate.

1 files changed, 8 insertions, 1 deletions

diff --git a/gdb/target.h b/gdb/target.h
index 37e4edb..0b85adf 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -471,7 +471,7 @@ struct target_ops
     ptid_t (*to_wait) (struct target_ops *,
 		       ptid_t, struct target_waitstatus *,
 		       int TARGET_DEBUG_PRINTER (target_debug_print_options))
-      TARGET_DEFAULT_NORETURN (noprocess ());
+      TARGET_DEFAULT_FUNC (default_target_wait);
     void (*to_fetch_registers) (struct target_ops *, struct regcache *, int)
       TARGET_DEFAULT_IGNORE ();
     void (*to_store_registers) (struct target_ops *, struct regcache *, int)
@@ -1327,6 +1327,13 @@ extern void target_resume (ptid_t ptid, int step, enum gdb_signal signal);
 extern ptid_t target_wait (ptid_t ptid, struct target_waitstatus *status,
 			   int options);
 
+/* The default target_ops::to_wait implementation.  */
+
+extern ptid_t default_target_wait (struct target_ops *ops,
+				   ptid_t ptid,
+				   struct target_waitstatus *status,
+				   int options);
+
 /* Fetch at least register REGNO, or all regs if regno == -1.  No result.  */
 
 extern void target_fetch_registers (struct regcache *regcache, int regno);