[patch] Fix threaded inferiors in child after fork

Jan Kratochvil
2008-01-02T10:34:03Z

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Hi,

if in the `set follow-fork-mode child' mode one gets into the forked child
where the child creates new thread GDB still does not have the threads support
initialized there and behaves erratically.

In fact the testcase may be redundant as it is just a part of another testcase
for the watchpoints-after-fork patch going to be sent now.

Regards,
Jan

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2008-01-02 Jan Kratochvil <jan.kratochvil@redhat.com>

* linux-nat.c (linux_child_follow_fork): Call also CHECK_FOR_THREAD_DB.

2008-01-02 Jan Kratochvil <jan.kratochvil@redhat.com>

* gdb.threads/fork-child-threads.exp, gdb.threads/fork-child-threads.c:
New files

--- ./gdb/linux-nat.c 1 Jan 2008 22:53:11 -0000 1.71
+++ ./gdb/linux-nat.c 2 Jan 2008 10:24:08 -0000
@@ -517,6 +517,7 @@ linux_child_follow_fork (struct target_o

push_target (ops);
linux_nat_switch_fork (inferior_ptid);
+ check_for_thread_db ();

/* Reset breakpoints in the child as appropriate. */
follow_inferior_reset_breakpoints ();
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/fork-child-threads.c 2 Jan 2008 10:24:09 -0000
@@ -0,0 +1,53 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2008 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/>.
+
+ Please email any bugs, comments, and/or additions to this file to:
+ bug-gdb@prep.ai.mit.edu */
+
+#include <pthread.h>
+#include <assert.h>
+#include <unistd.h>
+
+static void *
+start (void *arg)
+{
+ assert (0);
+ return arg;
+}
+
+int main(void)
+{
+ pthread_t thread;
+ int i;
+
+ switch (fork ())
+ {
+ case -1:
+ assert (0);
+ default:
+ break;
+ case 0:
+ i = pthread_create (&thread, NULL, start, NULL);
+ assert (i == 0);
+ i = pthread_join (thread, NULL);
+ assert (i == 0);
+
+ assert (0);
+ }
+
+ return 0;
+}
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ ./gdb/testsuite/gdb.threads/fork-child-threads.exp 2 Jan 2008 10:24:09 -0000
@@ -0,0 +1,47 @@
+# Copyright (C) 2008 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/>. */
+
+# Please email any bugs, comments, and/or additions to this file to:
+# bug-gdb@prep.ai.mit.edu
+
+set testfile fork-child-threads
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+ return -1
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+
+gdb_load ${binfile}
+if ![runto_main] then {
+ fail "Can't run to main"
+ return 0
+}
+
+gdb_test "set follow-fork-mode child"
+gdb_breakpoint "start"
+gdb_test "continue" "Breakpoint 2, start.*" "get to the spawned thread"
+
+# Wrong:
+# * 2 LWP 4466 start (arg=0x0) at fork-child-threads.c:28
+# Correct:
+# * 3 Thread 0x40a00950 (LWP 5553) start (arg=0x0) at ../.././gdb/testsuite/gdb.threads/fork-child-threads.c:28
+# 2 Thread 0x2aaaaaac3000 (LWP 5552) 0x00000031674076dd in pthread_join (threadid=<value optimized out>, thread_return=<value optimized out>) at pthread_join.c:89
+
+gdb_test "info threads" " Thread .* Thread .*" "two threads found"