[patch] Fix threaded inferiors in child after fork

[patch] Fix threaded inferiors in child after fork

[Jan Kratochvil]

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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"

Re: [patch] Fix threaded inferiors in child after fork

[Daniel Jacobowitz]

On Wed, Jan 02, 2008 at 11:29:12AM +0100, Jan Kratochvil wrote:
> +   Please email any bugs, comments, and/or additions to this file to:
> +   bug-gdb@prep.ai.mit.edu  */

Please delete this bit from the C file and exp file; that host is
long-gone.

> +gdb_test "set follow-fork-mode child"

Let's limit this test to GNU/Linux only; otherwise you have to figure
out if the current target supports it.

Otherwise this is OK.  Thanks.

-- 
Daniel Jacobowitz
CodeSourcery

Re: [patch] Fix threaded inferiors in child after fork

[Jan Kratochvil]

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On Wed, 02 Jan 2008 13:45:12 +0100, Daniel Jacobowitz wrote:
> On Wed, Jan 02, 2008 at 11:29:12AM +0100, Jan Kratochvil wrote:
> > +   Please email any bugs, comments, and/or additions to this file to:
> > +   bug-gdb@prep.ai.mit.edu  */
> 
> Please delete this bit from the C file and exp file; that host is
> long-gone.

Done.

> > +gdb_test "set follow-fork-mode child"
> 
> Let's limit this test to GNU/Linux only; otherwise you have to figure
> out if the current target supports it.

Done.

> Otherwise this is OK.  Thanks.

Committed the attached patch.


Thanks,
Jan

[-- Attachment #2: gdb-cvs-fork-child-threads2.patch --]
[-- Type: text/plain, Size: 3950 bytes --]

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 12:57:23 -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 12:57:23 -0000
@@ -0,0 +1,50 @@
+/* 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/>.  */
+
+#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 12:57:23 -0000
@@ -0,0 +1,49 @@
+# 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/>.
+
+# Only GNU/Linux is known to support `set follow-fork-mode child'.
+if { ! [istarget "*-*-linux*"] } {
+    return 0
+}
+
+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"