[RFA] Unify async setting.

[Vladimir Prus <vladimir@codesourcery.com>]

Presently, one need to use different commands to request async mode for linux
native and for async targets, which is hard on frontends.  Furthermore, the
relevant variables merely *allow* async mode, and there's no way for frontend
to make sure that async mode is actually in effect. This patch makes two things:

- Converts target-specific variables into a single 'set async' command.
- Adds new MI -list-target-features command that allows to check if current
target is in async mode.

The bulk of the patch is actually written by Pedro, I've only added MI/testsuite/doc
bits.

OK?

- Volodya

	* target.c (target_async_permitted, target_async_permitted_1)
	(set_maintenance_target_async_permitted)
	(show_maintenance_target_async_permitted): New.
	(initialize_targets): Register 'set target-async'.
	* target.h (target_async_permitted): Declare.
	* linux-nat.c (linux_nat_async_enabled)
	(linux_nat_async_permitted, set_maintenance_linux_async_permitted)
	(show_maintenance_linux_async_permitted): Remove.
	(sigchld_handler, linux_nat_is_async_p, linux_nat_can_async_p)
	(get_pending_events, linux_nat_async): Use target_async_permitted.
	(linux_nat_set_async_mode): Remove, moving the only used bits
	into...
	(linux_nat_setup_async): This.
	(_initialize_linux_nat): Do not register 'maint set linux-async'.
	Use linux_nat_setup_async.
	* remote.c (remote_async_permitted, remote_async_permitted_set)
	(set_maintenance_remote_async_permitted)
	(show_maintenance_remote_async_permitted): Remove.
	(remote_open_1, remote_terminal_inferior, remote_can_async_p)
	(remote_is_async_p): Use target_async_permitted.
	(_initialize_remote): Don't register 'main set remote-async'.
	* mi/mi-cmds.c (mi_cmds): Register -list-target-features.
	* mi/mi-cmds.h (mi_cmd_list_target_features): New.
	* mi/mi-main.c (mi_cmd_list_target_features): New.

	[testsuite/ChangeLog]
	* gdb.mi/mi-async.exp: Use 'set target-async'.
	* lib/mi-support.exp: Use 'set/show target-async'.

	[doc/ChangeLog]
	* gdb.texinfo (Background execution): Adjust example
	(GDB/MI Miscellaneous Commands): Document -list-target-features.
---
 gdb/doc/gdb.texinfo               |   33 +++++++++++--
 gdb/linux-nat.c                   |  101 +++++++-----------------------------
 gdb/mi/mi-cmds.c                  |    1 +
 gdb/mi/mi-cmds.h                  |    1 +
 gdb/mi/mi-main.c                  |   20 +++++++-
 gdb/remote.c                      |   54 +++-----------------
 gdb/target.c                      |   39 ++++++++++++++
 gdb/target.h                      |    4 ++
 gdb/testsuite/gdb.mi/mi-async.exp |    2 +-
 gdb/testsuite/lib/mi-support.exp  |    4 +-
 10 files changed, 124 insertions(+), 135 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 1ef4c8a..3ba9a59 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -4572,12 +4572,9 @@ independently and simultaneously.
 To enter non-stop mode, use this sequence of commands before you run
 or attach to your program:
 
-@c FIXME: can we fix this recipe to avoid the linux-async/remote-async details?
-
 @smallexample
 # Enable the async interface.  
-# For target remote, use remote-async instead of linux-async.
-maint set linux-async 1
+set async 1
 
 # If using the CLI, pagination breaks non-stop.
 set pagination off
@@ -22637,6 +22634,34 @@ option to the @code{-break-insert} command.
 
 @end itemize
 
+@subheading The @code{-list-target-features} Command
+@findex -list-target-features
+
+Returns a list of particular features that are supported by the
+target.  Those features affect the permitted MI commands, but 
+unlike the features reported by the @code{-list-features} command, the
+features depend on which target GDB is using at the moment.  Whenever
+a target can change, due to commands such as @code{-target-select},
+@code{-target-attach} or @code{-exec-run}, the list of target features
+may change, and the frontend should obtain it again.
+Example output:
+
+@smallexample
+(gdb) -list-features
+^done,result=["async"]
+@end smallexample
+
+The current list of features is:
+
+@itemize @minus
+@item
+@samp{async}---indicates that the target is capable of asynchronous
+command execution, which means that GDB will accept further commands
+even while the target is running.
+
+@end itemize
+
+
 @subheading The @code{-interpreter-exec} Command
 @findex -interpreter-exec
 
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index b59a35c..b25104e 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -276,9 +276,6 @@ static int linux_supports_tracevforkdone_flag = -1;
 
 /* Async mode support */
 
-/* True if async mode is currently on.  */
-static int linux_nat_async_enabled;
-
 /* Zero if the async mode, although enabled, is masked, which means
    linux_nat_wait should behave as if async mode was off.  */
 static int linux_nat_async_mask_value = 1;
@@ -3205,7 +3202,7 @@ linux_nat_pid_to_str (ptid_t ptid)
 static void
 sigchld_handler (int signo)
 {
-  if (linux_nat_async_enabled
+  if (target_async_permitted
       && linux_nat_async_events_state != sigchld_sync
       && signo == SIGCHLD)
     /* It is *always* a bug to hit this.  */
@@ -3992,45 +3989,15 @@ linux_trad_target (CORE_ADDR (*register_u_offset)(struct gdbarch *, int, int))
   return t;
 }
 
-/* Controls if async mode is permitted.  */
-static int linux_async_permitted = 0;
-
-/* The set command writes to this variable.  If the inferior is
-   executing, linux_nat_async_permitted is *not* updated.  */
-static int linux_async_permitted_1 = 0;
-
-static void
-set_maintenance_linux_async_permitted (char *args, int from_tty,
-			       struct cmd_list_element *c)
-{
-  if (target_has_execution)
-    {
-      linux_async_permitted_1 = linux_async_permitted;
-      error (_("Cannot change this setting while the inferior is running."));
-    }
-
-  linux_async_permitted = linux_async_permitted_1;
-  linux_nat_set_async_mode (linux_async_permitted);
-}
-
-static void
-show_maintenance_linux_async_permitted (struct ui_file *file, int from_tty,
-			    struct cmd_list_element *c, const char *value)
-{
-  fprintf_filtered (file, _("\
-Controlling the GNU/Linux inferior in asynchronous mode is %s.\n"),
-		    value);
-}
-
 /* target_is_async_p implementation.  */
 
 static int
 linux_nat_is_async_p (void)
 {
   /* NOTE: palves 2008-03-21: We're only async when the user requests
-     it explicitly with the "maintenance set linux-async" command.
+     it explicitly with the "maintenance set target-async" command.
      Someday, linux will always be async.  */
-  if (!linux_async_permitted)
+  if (!target_async_permitted)
     return 0;
 
   return 1;
@@ -4042,9 +4009,9 @@ static int
 linux_nat_can_async_p (void)
 {
   /* NOTE: palves 2008-03-21: We're only async when the user requests
-     it explicitly with the "maintenance set linux-async" command.
+     it explicitly with the "maintenance set target-async" command.
      Someday, linux will always be async.  */
-  if (!linux_async_permitted)
+  if (!target_async_permitted)
     return 0;
 
   /* See target.h/target_async_mask.  */
@@ -4125,7 +4092,7 @@ get_pending_events (void)
 {
   int status, options, pid;
 
-  if (!linux_nat_async_enabled
+  if (!target_async_permitted
       || linux_nat_async_events_state != sigchld_async)
     internal_error (__FILE__, __LINE__,
 		    "get_pending_events called with async masked");
@@ -4329,7 +4296,7 @@ static void
 linux_nat_async (void (*callback) (enum inferior_event_type event_type,
 				   void *context), void *context)
 {
-  if (linux_nat_async_mask_value == 0 || !linux_nat_async_enabled)
+  if (linux_nat_async_mask_value == 0 || !target_async_permitted)
     internal_error (__FILE__, __LINE__,
 		    "Calling target_async when async is masked");
 
@@ -4353,35 +4320,6 @@ linux_nat_async (void (*callback) (enum inferior_event_type event_type,
   return;
 }
 
-/* Enable/Disable async mode.  */
-
-static void
-linux_nat_set_async_mode (int on)
-{
-  if (linux_nat_async_enabled != on)
-    {
-      if (on)
-	{
-	  gdb_assert (waitpid_queue == NULL);
-	  if (pipe (linux_nat_event_pipe) == -1)
-	    internal_error (__FILE__, __LINE__,
-			    "creating event pipe failed.");
-	  fcntl (linux_nat_event_pipe[0], F_SETFL, O_NONBLOCK);
-	  fcntl (linux_nat_event_pipe[1], F_SETFL, O_NONBLOCK);
-	}
-      else
-	{
-	  drain_queued_events (-1);
-	  linux_nat_num_queued_events = 0;
-	  close (linux_nat_event_pipe[0]);
-	  close (linux_nat_event_pipe[1]);
-	  linux_nat_event_pipe[0] = linux_nat_event_pipe[1] = -1;
-
-	}
-    }
-  linux_nat_async_enabled = on;
-}
-
 static int
 send_sigint_callback (struct lwp_info *lp, void *data)
 {
@@ -4478,6 +4416,18 @@ linux_nat_get_siginfo (ptid_t ptid)
   return &lp->siginfo;
 }
 
+/* Enable/Disable async mode.  */
+
+static void
+linux_nat_setup_async (void)
+{
+  if (pipe (linux_nat_event_pipe) == -1)
+    internal_error (__FILE__, __LINE__,
+		    "creating event pipe failed.");
+  fcntl (linux_nat_event_pipe[0], F_SETFL, O_NONBLOCK);
+  fcntl (linux_nat_event_pipe[1], F_SETFL, O_NONBLOCK);
+}
+
 void
 _initialize_linux_nat (void)
 {
@@ -4510,16 +4460,6 @@ Enables printf debugging output."),
 			    show_debug_linux_nat_async,
 			    &setdebuglist, &showdebuglist);
 
-  add_setshow_boolean_cmd ("linux-async", class_maintenance,
-			   &linux_async_permitted_1, _("\
-Set whether gdb controls the GNU/Linux inferior in asynchronous mode."), _("\
-Show whether gdb controls the GNU/Linux inferior in asynchronous mode."), _("\
-Tells gdb whether to control the GNU/Linux inferior in asynchronous mode."),
-			   set_maintenance_linux_async_permitted,
-			   show_maintenance_linux_async_permitted,
-			   &maintenance_set_cmdlist,
-			   &maintenance_show_cmdlist);
-
   /* Get the default SIGCHLD action.  Used while forking an inferior
      (see linux_nat_create_inferior/linux_nat_async_events).  */
   sigaction (SIGCHLD, NULL, &sigchld_default_action);
@@ -4551,8 +4491,7 @@ Tells gdb whether to control the GNU/Linux inferior in asynchronous mode."),
   sigemptyset (&async_sigchld_action.sa_mask);
   async_sigchld_action.sa_flags = SA_RESTART;
 
-  /* Install the default mode.  */
-  linux_nat_set_async_mode (linux_async_permitted);
+  linux_nat_setup_async ();
 
   add_setshow_boolean_cmd ("disable-randomization", class_support,
 			   &disable_randomization, _("\
diff --git a/gdb/mi/mi-cmds.c b/gdb/mi/mi-cmds.c
index 3ae4c95..ca0f428 100644
--- a/gdb/mi/mi-cmds.c
+++ b/gdb/mi/mi-cmds.c
@@ -89,6 +89,7 @@ struct mi_cmd mi_cmds[] =
   { "inferior-tty-show", { NULL, 0 }, mi_cmd_inferior_tty_show},
   { "interpreter-exec", { NULL, 0 }, mi_cmd_interpreter_exec},
   { "list-features", { NULL, 0 }, mi_cmd_list_features},
+  { "list-target-features", { NULL, 0 }, mi_cmd_list_target_features},
   { "overlay-auto", { NULL, 0 }, NULL },
   { "overlay-list-mapping-state", { NULL, 0 }, NULL },
   { "overlay-list-overlays", { NULL, 0 }, NULL },
diff --git a/gdb/mi/mi-cmds.h b/gdb/mi/mi-cmds.h
index 72e18c7..16887ae 100644
--- a/gdb/mi/mi-cmds.h
+++ b/gdb/mi/mi-cmds.h
@@ -66,6 +66,7 @@ extern mi_cmd_argv_ftype mi_cmd_inferior_tty_set;
 extern mi_cmd_argv_ftype mi_cmd_inferior_tty_show;
 extern mi_cmd_argv_ftype mi_cmd_interpreter_exec;
 extern mi_cmd_argv_ftype mi_cmd_list_features;
+extern mi_cmd_argv_ftype mi_cmd_list_target_features;
 extern mi_cmd_argv_ftype mi_cmd_stack_info_depth;
 extern mi_cmd_argv_ftype mi_cmd_stack_info_frame;
 extern mi_cmd_argv_ftype mi_cmd_stack_list_args;
diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
index 733fc47..b18326d 100644
--- a/gdb/mi/mi-main.c
+++ b/gdb/mi/mi-main.c
@@ -915,7 +915,25 @@ mi_cmd_list_features (char *command, char **argv, int argc)
 
   error ("-list-features should be passed no arguments");
 }
- 
+
+void
+mi_cmd_list_target_features (char *command, char **argv, int argc)
+{
+  if (argc == 0)
+    {
+      struct cleanup *cleanup = NULL;
+      cleanup = make_cleanup_ui_out_list_begin_end (uiout, "features");      
+
+      if (target_can_async_p ())
+	ui_out_field_string (uiout, NULL, "async");
+      
+      do_cleanups (cleanup);
+      return;
+    }
+
+  error ("-list-target-features should be passed no arguments");
+}
+
 /* Execute a command within a safe environment.
    Return <0 for error; >=0 for ok.
 
diff --git a/gdb/remote.c b/gdb/remote.c
index 2782d05..af3b0b8 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -209,33 +209,6 @@ static void show_remote_protocol_packet_cmd (struct ui_file *file,
 
 void _initialize_remote (void);
 
-/* Controls if async mode is permitted.  */
-static int remote_async_permitted = 0;
-
-static int remote_async_permitted_set = 0;
-
-static void
-set_maintenance_remote_async_permitted (char *args, int from_tty,
-					struct cmd_list_element *c)
-{
-  if (target_has_execution)
-    {
-      remote_async_permitted_set = remote_async_permitted; /* revert */
-      error (_("Cannot change this setting while the inferior is running."));
-    }
-
-  remote_async_permitted = remote_async_permitted_set;
-}
-
-static void
-show_maintenance_remote_async_permitted (struct ui_file *file, int from_tty,
-					 struct cmd_list_element *c, const char *value)
-{
-  fprintf_filtered (file, _("\
-Controlling the remote inferior in asynchronous mode is %s.\n"),
-		    value);
-}
-
 /* For "remote".  */
 
 static struct cmd_list_element *remote_cmdlist;
@@ -2703,7 +2676,7 @@ remote_open_1 (char *name, int from_tty, struct target_ops *target, int extended
 	   "(e.g. /dev/ttyS0, /dev/ttya, COM1, etc.)."));
 
   /* See FIXME above.  */
-  if (!remote_async_permitted)
+  if (!target_async_permitted)
     wait_forever_enabled_p = 1;
 
   /* If we're connected to a running target, target_preopen will kill it.
@@ -2824,7 +2797,7 @@ remote_open_1 (char *name, int from_tty, struct target_ops *target, int extended
      this before anything involving memory or registers.  */
   target_find_description ();
 
-  if (remote_async_permitted)
+  if (target_async_permitted)
     {
       /* With this target we start out by owning the terminal.  */
       remote_async_terminal_ours_p = 1;
@@ -2869,13 +2842,13 @@ remote_open_1 (char *name, int from_tty, struct target_ops *target, int extended
     if (ex.reason < 0)
       {
 	pop_target ();
-	if (remote_async_permitted)
+	if (target_async_permitted)
 	  wait_forever_enabled_p = 1;
 	throw_exception (ex);
       }
   }
 
-  if (remote_async_permitted)
+  if (target_async_permitted)
     wait_forever_enabled_p = 1;
 
   if (extended_p)
@@ -3403,7 +3376,7 @@ Give up (and stop debugging it)? "))
 static void
 remote_terminal_inferior (void)
 {
-  if (!remote_async_permitted)
+  if (!target_async_permitted)
     /* Nothing to do.  */
     return;
 
@@ -3433,7 +3406,7 @@ remote_terminal_inferior (void)
 static void
 remote_terminal_ours (void)
 {
-  if (!remote_async_permitted)
+  if (!target_async_permitted)
     /* Nothing to do.  */
     return;
 
@@ -7265,7 +7238,7 @@ Specify the serial device it is connected to (e.g. /dev/ttya).";
 static int
 remote_can_async_p (void)
 {
-  if (!remote_async_permitted)
+  if (!target_async_permitted)
     /* We only enable async when the user specifically asks for it.  */
     return 0;
 
@@ -7276,7 +7249,7 @@ remote_can_async_p (void)
 static int
 remote_is_async_p (void)
 {
-  if (!remote_async_permitted)
+  if (!target_async_permitted)
     /* We only enable async when the user specifically asks for it.  */
     return 0;
 
@@ -7630,17 +7603,6 @@ Set the remote pathname for \"run\""), _("\
 Show the remote pathname for \"run\""), NULL, NULL, NULL,
 				   &remote_set_cmdlist, &remote_show_cmdlist);
 
-  add_setshow_boolean_cmd ("remote-async", class_maintenance,
-			   &remote_async_permitted_set, _("\
-Set whether gdb controls the remote inferior in asynchronous mode."), _("\
-Show whether gdb controls the remote inferior in asynchronous mode."), _("\
-Tells gdb whether to control the remote inferior in asynchronous mode."),
-			   set_maintenance_remote_async_permitted,
-			   show_maintenance_remote_async_permitted,
-			   &maintenance_set_cmdlist,
-			   &maintenance_show_cmdlist);
-
-
   /* Eventually initialize fileio.  See fileio.c */
   initialize_remote_fileio (remote_set_cmdlist, remote_show_cmdlist);
 
diff --git a/gdb/target.c b/gdb/target.c
index 6cda095..0dbe49b 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -3136,6 +3136,35 @@ maintenance_print_target_stack (char *cmd, int from_tty)
     }
 }
 
+/* Controls if async mode is permitted.  */
+int target_async_permitted = 0;
+
+/* The set command writes to this variable.  If the inferior is
+   executing, linux_nat_async_permitted is *not* updated.  */
+static int target_async_permitted_1 = 0;
+
+static void
+set_maintenance_target_async_permitted (char *args, int from_tty,
+					struct cmd_list_element *c)
+{
+  if (target_has_execution)
+    {
+      target_async_permitted_1 = target_async_permitted;
+      error (_("Cannot change this setting while the inferior is running."));
+    }
+
+  target_async_permitted = target_async_permitted_1;
+}
+
+static void
+show_maintenance_target_async_permitted (struct ui_file *file, int from_tty,
+					 struct cmd_list_element *c,
+					 const char *value)
+{
+  fprintf_filtered (file, _("\
+Controlling the inferior in asynchronous mode is %s.\n"), value);
+}
+
 void
 initialize_targets (void)
 {
@@ -3173,5 +3202,15 @@ result in significant performance improvement for remote targets."),
            _("Print the name of each layer of the internal target stack."),
            &maintenanceprintlist);
 
+  add_setshow_boolean_cmd ("target-async", no_class,
+			   &target_async_permitted_1, _("\
+Set whether gdb controls the inferior in asynchronous mode."), _("\
+Show whether gdb controls the inferior in asynchronous mode."), _("\
+Tells gdb whether to control the inferior in asynchronous mode."),
+			   set_maintenance_target_async_permitted,
+			   show_maintenance_target_async_permitted,
+			   &setlist,
+			   &showlist);
+
   target_dcache = dcache_init ();
 }
diff --git a/gdb/target.h b/gdb/target.h
index e242566..3a1d4b7 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -956,6 +956,10 @@ int target_follow_fork (int follow_child);
 #define target_can_lock_scheduler \
      (current_target.to_has_thread_control & tc_schedlock)
 
+/* Should the target enable async mode if it is supported?  Temporary
+   cludge until async mode is a strict superset of sync mode.  */
+extern int target_async_permitted;
+
 /* Can the target support asynchronous execution? */
 #define target_can_async_p() (current_target.to_can_async_p ())
 
diff --git a/gdb/testsuite/gdb.mi/mi-async.exp b/gdb/testsuite/gdb.mi/mi-async.exp
index 9ac91fd..a251c32 100644
--- a/gdb/testsuite/gdb.mi/mi-async.exp
+++ b/gdb/testsuite/gdb.mi/mi-async.exp
@@ -27,7 +27,7 @@ if { !([isnative] && [istarget *-linux*]) \
 
 # The plan is for async mode to become the default but toggle for now.
 set saved_gdbflags $GDBFLAGS
-set GDBFLAGS [concat $GDBFLAGS " -ex \"maint set linux-async on\""]
+set GDBFLAGS [concat $GDBFLAGS " -ex \"set target-async on\""]
 
 load_lib mi-support.exp
 
diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index 762e4e2..09d3eeb 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -912,10 +912,10 @@ proc detect_async {} {
     global async
     global mi_gdb_prompt
 
-    send_gdb "maint show linux-async\n"
+    send_gdb "show target-async\n"
         
     gdb_expect {
-        -re ".*Controlling the GNU/Linux inferior in asynchronous mode is on...*$mi_gdb_prompt$" {
+        -re ".*Controlling the inferior in asynchronous mode is on...*$mi_gdb_prompt$" {
             set async 1
         }
         -re ".*$mi_gdb_prompt$" {
-- 
1.5.3.5