Fix 'gcore' with exited threads

Program received signal SIGABRT, Aborted.
[...]
(gdb) gcore foobar
Couldn't get registers: No such process.
(gdb) info threads
[...]
(gdb) gcore foobar
Saved corefile foobar
(gdb)

gcore tries to access the exited thread:
[Thread 0x7ffff7fce700 (LWP 6895) exited]
ptrace(PTRACE_GETREGS, 6895, 0, 0x7fff18167dd0) = -1 ESRCH (No such process)

Without the TRY_CATCH protection testsuite FAILs for:
	gcore .../gdb/testsuite/gdb.threads/gcore-thread0.test
	Cannot find new threads: debugger service failed
	(gdb) FAIL: gdb.threads/gcore-thread.exp: save a zeroed-threads corefile
	+
	core .../gdb/testsuite/gdb.threads/gcore-thread0.test
	".../gdb/testsuite/gdb.threads/gcore-thread0.test" is not a core dump: File format not recognized
	(gdb) FAIL: gdb.threads/gcore-thread.exp: core0file: re-load generated corefile (bad file format)
Maybe the TRY_CATCH could be more inside update_thread_list().

Similar update_thread_list() call is IMO missing in procfs_make_note_section()
but I do not have where to verify that change.

gdb/ChangeLog
2014-08-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* linux-tdep.c (linux_corefile_thread_callback): Ignore THREAD_EXITED.
	(linux_make_corefile_notes): call update_thread_list, protected against
	exceptions.

gdb/testsuite/ChangeLog
2014-08-21  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.threads/gcore-stale-thread.c: New file.
	* gdb.threads/gcore-stale-thread.exp: New file.

2 files changed, 105 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.threads/gcore-stale-thread.c b/gdb/testsuite/gdb.threads/gcore-stale-thread.c
new file mode 100644
index 0000000..944acba
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/gcore-stale-thread.c
@@ -0,0 +1,48 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014 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 <pthread.h>
+#include <assert.h>
+
+static pthread_t main_thread;
+
+static void *
+start (void *arg)
+{
+  int i;
+
+  i = pthread_join (main_thread, NULL);
+  assert (i == 0);
+
+  return arg; /* break-here */
+}
+
+int
+main (void)
+{
+  pthread_t thread;
+  int i;
+
+  main_thread = pthread_self ();
+
+  i = pthread_create (&thread, NULL, start, NULL);
+  assert (i == 0);
+
+  pthread_exit (NULL);
+  assert (0);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/gcore-stale-thread.exp b/gdb/testsuite/gdb.threads/gcore-stale-thread.exp
new file mode 100644
index 0000000..291c56f
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/gcore-stale-thread.exp
@@ -0,0 +1,57 @@
+# Copyright 2014 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/>.
+
+standard_testfile
+set corefile [standard_output_file ${testfile}.core]
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable debug] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+gdb_test_no_output "set non-stop on"
+
+if { ! [ runto_main ] } then {
+    return -1
+}
+
+gdb_test_multiple "info threads" "threads are supported" {
+    -re ".* main .*\r\n$gdb_prompt $" {
+	# OK, threads are supported.
+    }
+    -re "\r\n$gdb_prompt $" {
+	unsupported "gdb does not support threads on this target"
+	return -1
+    }
+}
+
+gdb_breakpoint ${srcfile}:[gdb_get_line_number "break-here"]
+# gdb_continue_to_breakpoint does not work as it uses "$gdb_prompt $" regex
+# which does not work due to the output: (gdb) [Thread ... exited]
+set name "continue to breakpoint: break-here"
+gdb_test_multiple "continue" $name {
+    -re "Breakpoint .* (at|in) .* break-here .*\r\n$gdb_prompt " {
+	pass $name
+    }
+}
+
+gdb_gcore_cmd "$corefile" "save a corefile"
+
+# Do not run "info threads" before "gcore" as it could workaround the bug
+# by discarding non-current exited threads.
+gdb_test "info threads" \
+         {The current thread <Thread ID 1> has terminated\.  See `help thread'\.} \
+	 "exited thread is current due to non-stop"