Fix "source" with interpreter-exec

PR mi/15811 points out that "source"ing a file that uses
interpreter-exec will put gdb in a weird state, where the CLI stops
working.  The bug is that tui_interp::suspend does not unregister the
event file descriptor.

The test case is from Andrew Burgess.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=15811

gdb/testsuite/gdb.base/interpreter-exec.gdb

diff --git a/gdb/testsuite/gdb.base/interpreter-exec.gdb b/gdb/testsuite/gdb.base/interpreter-exec.gdb
new file mode 100644
index 0000000..434a4ad
--- /dev/null
+++ b/gdb/testsuite/gdb.base/interpreter-exec.gdb
@@ -0,0 +1,20 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2013-2022 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 GDB's "source" command for scripts containing interpreter-exec.
+
+interpreter-exec mi "-gdb-show verbose"

gdb/testsuite/gdb.base/source.exp

diff --git a/gdb/testsuite/gdb.base/source.exp b/gdb/testsuite/gdb.base/source.exp
index 3d72b50..9884a72 100644
--- a/gdb/testsuite/gdb.base/source.exp
+++ b/gdb/testsuite/gdb.base/source.exp
@@ -73,3 +73,9 @@
 		"source-error-1.gdb:21: Error in sourced command file:" \
 		"Cannot access memory at address 0x0" ] \
     "script contains error"
+
+# There was a case where sourcing a script containing "interpreter-exec"
+# commands would corrupt the interpreter mechanism and crash gdb.
+gdb_test "source ${srcdir}/${subdir}/interpreter-exec.gdb" \
+    "\\^done,value=\"off\"" \
+    "source interpreter-exec"

gdb/tui/tui-interp.c

diff --git a/gdb/tui/tui-interp.c b/gdb/tui/tui-interp.c
index 1c4ffbb..e0846fe 100644
--- a/gdb/tui/tui-interp.c
+++ b/gdb/tui/tui-interp.c
@@ -135,6 +135,7 @@ tui_interp::resume ()
 void
 tui_interp::suspend ()
 {
+  gdb_disable_readline ();
   tui_start_enabled = tui_active;
   tui_disable ();
 }