[BUG][PANIC] cgroup panics with mmotm for 2.6.28-rc7

[Balbir Singh <balbir@linux.vnet.ibm.com>]

Hi, Paul,

I see the following stack trace when I run my tests. I've not yet
investigated the problem.

------------[ cut here ]------------
kernel BUG at kernel/cgroup.c:392!
invalid opcode: 0000 [#1] SMP 
last sysfs file: /sys/devices/pci0000:00/0000:00:1c.5/0000:03:00.0/irq
CPU 1 
Modules linked in: coretemp hwmon kvm_intel kvm rtc_cmos rtc_core
rtc_lib mptsas mptscsih mptbase scsi_transport_sas uhci_hcd ohci_hcd
ehci_hcd
Pid: 3866, comm: libcgrouptest01 Tainted: G        W  2.6.28-rc7-mm1
#3
RIP: 0010:[<ffffffff80272c5b>]  [<ffffffff80272c5b>]
link_css_set+0xf/0x5a
RSP: 0018:ffff8800388ebda8  EFLAGS: 00010246
RAX: ffffffff807a2790 RBX: ffff88003e9667e0 RCX: ffff88012f6ecff8
RDX: ffff88012f6ecff8 RSI: ffff88003e9667e0 RDI: ffff8800388ebdf8
RBP: ffff8800388ebda8 R08: ffff8800388ebdf8 R09: 0000000000000000
R10: ffff88003a55d000 R11: ffffe2000196d170 R12: ffff88003e9667e0
R13: 0000000000000001 R14: ffff880038838000 R15: ffffffff811d3c00
FS:  00007f482219e700(0000) GS:ffff88007ff064b0(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007f48221cc000 CR3: 0000000038896000 CR4: 00000000000026e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process libcgrouptest01 (pid: 3866, threadinfo ffff8800388ea000, task
ffff880038838000)
Stack:
 ffff8800388ebe48 ffffffff802740dd ffffffff80272955 ffff88012f6ecff8
 ffff8800389b4028 ffff8800389b4000 ffffffff807aa720 ffff88012f6ecb68
 ffff88012fd852a8 0000000000000246 ffff8800388ebdf8 ffff8800388ebdf8
Call Trace:
 [<ffffffff802740dd>] cgroup_attach_task+0x234/0x3d0
 [<ffffffff80272955>] ? cgroup_lock_live_group+0x1a/0x36
 [<ffffffff80274380>] cgroup_tasks_write+0x107/0x12e
 [<ffffffff802742b8>] ? cgroup_tasks_write+0x3f/0x12e
 [<ffffffff802748d4>] cgroup_file_write+0xfb/0x22d
 [<ffffffff8039e30d>] ? __up_read+0x9b/0xa3
 [<ffffffff802ba77d>] vfs_write+0xae/0x157
 [<ffffffff802bac98>] sys_write+0x47/0x6f
 [<ffffffff8020bfdb>] system_call_fastpath+0x16/0x1b
Code: 8b 5b 30 48 39 c3 74 06 48 3b 5b 60 75 f1 48 39 c3 0f 94 c0 0f
b6 c0 5b 5a 5b c9 c3 4c 8b 07 55 48 89 d1 48 89 e5 49 39 f8 75 04 <0f>
0b eb fe 49 8b 40 08 49 8b 10 49 89 70 20 48 89 10 48 89 42 
RIP  [<ffffffff80272c5b>] link_css_set+0xf/0x5a
 RSP <ffff8800388ebda8>
---[ end trace b73399e271602d45 ]---

I've setup my system using libcgroup to create default cgroups and to
automatically classify all tasks to the "default group". I've made
some changes to cgconfig and cgred scripts (they can be found under
the source code of libcgroup (branches/balbir-tests).

Steps to reproduce

1. Start with the new scripts and move all tasks to a default cgroup
2. Ensure that cgred and cgconfig are running
3. Stop cgred and cgconfig and run libcgrouptest01 (patches posted by
sudhir on the libcgroup mailing list).

The test log is

WARN: /dev/cgroup_controllers-1 already exist..overwriting
C:DBG: fs_mounted as recieved from script=1
C:DBG: mountpoint1 as recieved from script=/dev/cgroup_controllers-1
sanity check pass. cgroup
TEST 1:PASS : cgroup_attach_task()               Ret Value = 50014
Par: nullcgroup
TEST 2:PASS : cgroup_init()                      Ret Value = 0  
TEST 3:PASS : cgroup_attach_task()               Ret Value = 0   Task
found in group/s
TEST 4:PASS : cgroup_attach_task_pid()           Ret Value = 50016
TEST 1:PASS : cgroup_new_cgroup()                Ret Value = 0  
TEST 2:PASS : cgroup_create_cgroup()             Ret Value = 0   grp
found in fs



-- 
	Balbir