gdb, btrace: make record-btrace per-inferior

When there is more than one inferior, the "record btrace" command should
only apply to the current inferior.

gdb/ChangeLog:

2020-03-19  Markus Metzger  <markus.t.metzger@intel.com>

	* record-btrace.c (record_btrace_enable_warn): Ignore thread if
	its inferior is not recorded by us.
	(record_btrace_target_open): Replace call to all_non_exited_threads ()
	with call to current_inferior ()->non_exited_threads ().
	(record_btrace_target::stop_recording): Likewise.
	(record_btrace_target::close): Likewise.
	(record_btrace_target::wait): Likewise.
	(record_btrace_target::record_stop_replaying): Likewise.

gdb/testsuite/ChangeLog:

2020-03-19  Markus Metzger  <markus.t.metzger@intel.com>

	* gdb.btrace/multi-inferior.c: New test.
	* gdb.btrace/multi-inferior.exp: New file.

1 files changed, 22 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.btrace/multi-inferior.c b/gdb/testsuite/gdb.btrace/multi-inferior.c
new file mode 100644
index 0000000..9d7b2f1
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/multi-inferior.c
@@ -0,0 +1,22 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 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/>.  */
+
+int
+main (void)
+{
+  return 0;
+}