enable target async by default; separate MI and target notions of async

This finally makes background execution commands possible by default.

However, in order to do that, there's one last thing we need to do --
we need to separate the MI and target notions of "async".  Unlike the
CLI, where the user explicitly requests foreground vs background
execution in the execution command itself (c vs c&), MI chose to treat
"set target-async" specially -- setting it changes the default
behavior of execution commands.

So, we can't simply "set target-async" default to on, as that would
affect MI frontends.  Instead we have to make the setting MI-specific,
and teach MI about sync commands on top of an async target.

Because the "target" word in "set target-async" ends up as a potential
source of confusion, the patch adds a "set mi-async" option, and makes
"set target-async" a deprecated alias.

Rather than make the targets always async, this patch introduces a new
"maint set target-async" option so that the GDB developer can control
whether the target is async.  This makes it simpler to debug issues
arising only in the synchronous mode; important because sync mode
seems unlikely to go away.

Unlike in previous revisions, "set target-async" does not affect this
new maint parameter.  The rationale for this is that then one can
easily run the test suite in the "maint set target-async off" mode and
have tests that enable mi-async fail just like they fail on
non-async-capable targets.  This emulation is exactly the point of the
maint option.

I had asked Tom in a previous iteration to split the actual change of
the target async default to a separate patch, but it turns out that
that is quite awkward in this version of the patch, because with MI
async and target async decoupled (unlike in previous versions), if we
don't flip the default at the same time, then just "set target-async
on" alone never actually manages to do anything.  It's best to not
have that transitory state in the tree.

Given "set target-async on" now only has effect for MI, the patch goes
through the testsuite removing it from non-MI tests.  MI tests are
adjusted to use the new and less confusing "mi-async" spelling.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* NEWS: Mention "maint set target-async", "set mi-async", and that
	background execution commands are now always available.
	* target.h (target_async_permitted): Update comment.
	* target.c (target_async_permitted, target_async_permitted_1):
	Default to 1.
	(set_target_async_command): Rename to ...
	(maint_set_target_async_command): ... this.
	(show_target_async_command): Rename to ...
	(maint_show_target_async_command): ... this.
	(_initialize_target): Adjust.
	* infcmd.c (prepare_execution_command): Make extern.
	* inferior.h (prepare_execution_command): Declare.
	* infrun.c (set_observer_mode): Leave target async alone.
	* mi/mi-interp.c (mi_interpreter_init): Install
	mi_on_sync_execution_done as sync_execution_done observer.
	(mi_on_sync_execution_done): New function.
	(mi_execute_command_input_handler): Don't print the prompt if we
	just started a synchronous command with an async target.
	(mi_on_resume): Check sync_execution before printing prompt.
	* mi/mi-main.h (mi_async_p): Declare.
	* mi/mi-main.c: Include gdbcmd.h.
	(mi_async_p): New function.
	(mi_async, mi_async_1): New globals.
	(set_mi_async_command, show_mi_async_command, mi_async): New
	functions.
	(exec_continue): Call prepare_execution_command.
	(run_one_inferior, mi_cmd_exec_run, mi_cmd_list_target_features)
	(mi_execute_async_cli_command): Use mi_async_p.
	(_initialize_mi_main): Install "set mi-async".  Make
	"target-async" a deprecated alias.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* gdb.texinfo (Non-Stop Mode): Remove "set target-async 1"
	from example.
	(Asynchronous and non-stop modes): Document '-gdb-set mi-async'.
	Mention that target-async is now deprecated.
	(Maintenance Commands): Document maint set/show target-async.

2014-05-29  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tromey@redhat.com>

	* gdb.base/async-shell.exp: Don't enable target-async.
	* gdb.base/async.exp
	* gdb.base/corefile.exp (corefile_test_attach): Remove 'async'
	parameter.  Adjust.
	(top level): Don't test with "target-async".
	* gdb.base/dprintf-non-stop.exp: Don't enable target-async.
	* gdb.base/gdb-sigterm.exp: Don't test with "target-async".
	* gdb.base/inferior-died.exp: Don't enable target-async.
	* gdb.base/interrupt-noterm.exp: Likewise.
	* gdb.mi/mi-async.exp: Use "mi-async" instead of "target-async".
	* gdb.mi/mi-nonstop-exit.exp: Likewise.
	* gdb.mi/mi-nonstop.exp: Likewise.
	* gdb.mi/mi-ns-stale-regcache.exp: Likewise.
	* gdb.mi/mi-nsintrall.exp: Likewise.
	* gdb.mi/mi-nsmoribund.exp: Likewise.
	* gdb.mi/mi-nsthrexec.exp: Likewise.
	* gdb.mi/mi-watch-nonstop.exp: Likewise.
	* gdb.multi/watchpoint-multi.exp: Adjust comment.
	* gdb.python/py-evsignal.exp: Don't enable target-async.
	* gdb.python/py-evthreads.exp: Likewise.
	* gdb.python/py-prompt.exp: Likewise.
	* gdb.reverse/break-precsave.exp: Don't test with "target-async".
	* gdb.server/solib-list.exp: Don't enable target-async.
	* gdb.threads/thread-specific-bp.exp: Likewise.
	* lib/mi-support.exp: Adjust to use mi-async.

2 files changed, 44 insertions, 19 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index f0e5804..18fb241 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,4 +1,13 @@
 2014-05-29  Pedro Alves  <palves@redhat.com>
+	    Tom Tromey  <tromey@redhat.com>
+
+	* gdb.texinfo (Non-Stop Mode): Remove "set target-async 1"
+	from example.
+	(Asynchronous and non-stop modes): Document '-gdb-set mi-async'.
+	Mention that target-async is now deprecated.
+	(Maintenance Commands): Document maint set/show target-async.
+
+2014-05-29  Pedro Alves  <palves@redhat.com>
 
 	* observer.texi (sync_execution_done, command_error): New
 	subjects.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 1ee62e0..9f7fa18 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -5778,9 +5778,6 @@ To enter non-stop mode, use this sequence of commands before you run
 or attach to your program:
 
 @smallexample
-# Enable the async interface.
-set target-async 1
-
 # If using the CLI, pagination breaks non-stop.
 set pagination off
 
@@ -5850,21 +5847,6 @@ the program to report that some thread has stopped before prompting for
 another command.  In background execution, @value{GDBN} immediately gives
 a command prompt so that you can issue other commands while your program runs.
 
-You need to explicitly enable asynchronous mode before you can use
-background execution commands.  You can use these commands to
-manipulate the asynchronous mode setting:
-
-@table @code
-@kindex set target-async
-@item set target-async on
-Enable asynchronous mode.
-@item set target-async off
-Disable asynchronous mode.
-@kindex show target-async
-@item show target-async
-Show the current target-async setting.
-@end table
-
 If the target doesn't support async mode, @value{GDBN} issues an error
 message if you attempt to use the background execution commands.
 
@@ -24818,12 +24800,37 @@ On some targets, @value{GDBN} is capable of processing MI commands
 even while the target is running.  This is called @dfn{asynchronous
 command execution} (@pxref{Background Execution}).  The frontend may
 specify a preferrence for asynchronous execution using the
-@code{-gdb-set target-async 1} command, which should be emitted before
+@code{-gdb-set mi-async 1} command, which should be emitted before
 either running the executable or attaching to the target.  After the
 frontend has started the executable or attached to the target, it can
 find if asynchronous execution is enabled using the
 @code{-list-target-features} command.
 
+@table @code
+@item -gdb-set mi-async on
+@item -gdb-set mi-async off
+Set whether MI is in asynchronous mode.
+
+When @code{off}, which is the default, MI execution commands (e.g.,
+@code{-exec-continue}) are foreground commands, and @value{GDBN} waits
+for the program to stop before processing further commands.
+
+When @code{on}, MI execution commands are background execution
+commands (e.g., @code{-exec-continue} becomes the equivalent of the
+@code{c&} CLI command), and so @value{GDBN} is capable of processing
+MI commands even while the target is running.
+
+@item -gdb-show mi-async
+Show whether MI asynchronous mode is enabled.
+@end table
+
+Note: In @value{GDBN} version 7.7 and earlier, this option was called
+@code{target-async} instead of @code{mi-async}, and it had the effect
+of both putting MI in asynchronous mode and making CLI background
+commands possible.  CLI background commands are now always possible
+``out of the box'' if the target supports them.  The old spelling is
+kept as a deprecated alias for backwards compatibility.
+
 Even if @value{GDBN} can accept a command while target is running,
 many commands that access the target do not work when the target is
 running.  Therefore, asynchronous command execution is most useful
@@ -33532,6 +33539,15 @@ Control whether to show all non zero areas within a 1k block starting
 at thread local base, when using the @samp{info w32 thread-information-block}
 command.
 
+@kindex maint set target-async
+@kindex maint show target-async
+@item maint set target-async
+@itemx maint show target-async
+This controls whether @value{GDBN} targets operate in synchronous or
+asynchronous mode (@pxref{Background Execution}).  Normally the
+default is asynchronous, if it is available; but this can be changed
+to more easily debug problems occurring only in synchronous mode.
+
 @kindex maint set per-command
 @kindex maint show per-command
 @item maint set per-command