gdb: Re-enable stdin for all UIs from start_event_loop

If we catch an exception in start_event_loop's call to
gdb_do_one_event, then it is possible that the current_ui has changed
since we called async_disable_stdin.  If that's the case then calling
async_enable_stdin will be called on the wrong UI.

To solve this problem we wrap the call to async_enable_stdin with
SWITCH_THRU_ALL_UIS, this causes us to try and re-enable stdin for all
UIs, which will catch any for which we called async_disable_stdin.

gdb/ChangeLog:

	* event-loop.c (start_event_loop): Wrap async_enable_stdin with
	SWITCH_THRU_ALL_UIS.

gdb/testsuite/ChangeLog:

	* gdb.server/multi-ui-errors.c: New file.
	* gdb.server/multi-ui-errors.exp: New file.

Change-Id: I1e18deff2e6f4e17f7a13adce3553eb001cad93b

gdb/ChangeLog

@@ -1,3 +1,8 @@
+2020-01-24  Andrew Burgess  <[email protected]>
+
+	* event-loop.c (start_event_loop): Wrap async_enable_stdin with
+	SWITCH_THRU_ALL_UIS.
+
 2020-01-24  Andrew Burgess  <[email protected]>
 
 	PR tui/9765

gdb/event-loop.c

@@ -376,7 +376,10 @@ start_event_loop (void)
 	  /* If any exception escaped to here, we better enable
 	     stdin.  Otherwise, any command that calls async_disable_stdin,
 	     and then throws, will leave stdin inoperable.  */
-	  async_enable_stdin ();
+	  SWITCH_THRU_ALL_UIS ()
+	    {
+	      async_enable_stdin ();
+	    }
 	  /* If we long-jumped out of do_one_event, we probably didn't
 	     get around to resetting the prompt, which leaves readline
 	     in a messed-up state.  Reset it here.  */

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2020-01-24  Andrew Burgess  <[email protected]>
+
+	* gdb.server/multi-ui-errors.c: New file.
+	* gdb.server/multi-ui-errors.exp: New file.
+
 2020-01-24  Andrew Burgess  <[email protected]>
 
 	PR tui/9765

gdb/testsuite/gdb.server/multi-ui-errors.c

@@ -0,0 +1,32 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2019-2020 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <unistd.h>
+
+int
+main (void)
+{
+  int i;
+
+  printf ("@@XX@@ Inferior Starting @@XX@@\n");
+
+  for (i = 0; i < 120; ++i)
+    sleep (1);
+
+  return 0;
+}

gdb/testsuite/gdb.server/multi-ui-errors.exp

@@ -0,0 +1,107 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2019-2020 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test what happens if we have multiple UIs in use, and an error
+# occurs while running a GDB command.  Specifically, do both UIs
+# return to an interactive state, or does one (or both) of them get
+# stuck in a non-interactive state.
+
+load_lib gdbserver-support.exp
+
+standard_testfile
+
+if {[skip_gdbserver_tests]} {
+    return 0
+}
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
+    return -1
+}
+
+# Make sure we're disconnected, in case we're testing with an
+# extended-remote board, therefore already connected.
+gdb_test "disconnect" ".*"
+
+# Start gdbserver.
+set res [gdbserver_spawn "${binfile}"]
+set gdbserver_protocol [lindex $res 0]
+set gdbserver_gdbport [lindex $res 1]
+set gdbserver_pid [exp_pid -i $server_spawn_id]
+
+# Save the main UI's spawn ID.
+set gdb_main_spawn_id $gdb_spawn_id
+
+# Create the new PTY for the secondary console UI, issue the 'new-ui'
+# command, and wait for a prompt on the second UI.
+spawn -pty
+set extra_spawn_id $spawn_id
+set extra_tty_name $spawn_out(slave,name)
+gdb_test_multiple "new-ui console $extra_tty_name" "new-ui" {
+    -re "New UI allocated\r\n$gdb_prompt $" {
+	pass $gdb_test_name
+    }
+}
+with_spawn_id $extra_spawn_id {
+    gdb_test_multiple "" "initial prompt on extra console" {
+	-re "$gdb_prompt $" {
+	    pass $gdb_test_name
+	}
+    }
+}
+
+# Connect to the remote and continue its execution from the other UI.
+with_spawn_id $extra_spawn_id {
+    gdb_test "target $gdbserver_protocol $gdbserver_gdbport" ".*"
+    send_gdb "continue\n"
+}
+
+# We're going to kill the gdbserver, but before we do, lets make sure
+# that the inferior has started executing.
+with_spawn_id $server_spawn_id {
+    gdb_test_multiple "" "ensure inferior is running" {
+	-re "@@XX@@ Inferior Starting @@XX@@" {
+	    pass $gdb_test_name
+	}
+	timeout {
+	    fail $gdb_test_name
+	}
+    }
+}
+
+# Interact with the main UI.
+with_spawn_id $gdb_main_spawn_id {
+    gdb_test "echo hello\\n" "hello" "interact with GDB's main UI"
+}
+
+# Now kill the gdbserver.
+remote_exec target "kill -9 $gdbserver_pid"
+
+# We expect to land back at a GDB prompt in both UIs, however there is
+# currently an issue that in the original UI GDB doesn't reprint its
+# prompt.  That said, getting a prompt isn't the point of this test.
+# The point is that we should be able to interact with GDB from either
+# interpreter now.
+
+with_spawn_id $gdb_main_spawn_id {
+    gdb_test "echo" "" \
+	"main UI, prompt after gdbserver dies"
+}
+
+with_spawn_id $extra_spawn_id {
+    gdb_test "echo" "" \
+	"extra UI, prompt after gdbserver dies"
+}