With patches 0-4 of f0.4 patched into a 2.6.11 kernel, I'm seeing a
ref-counting Oops when I run the following two commands in parallel:
A: while true; do mkdir /config/ckrm/foo; rmdir /config/ckrm/foo; done
B: while true; do echo $$ > /config/ckrm/foo/members; done
(This is basically the same test case that was a problem for e18).
I get a warning trigged in kref_get(), followed by an Oops in
ckrm_remove_child() - presumably the ckrm_add_member is adding a task
to a class whose refcount has already reached 0 and is in the process
of being destroyed - see the console dump below.
A solution would probably involve making rcfs or configfs hold
refcounts for every object that's accessible through the filesystem,
and not drop them until the object is no longer accessible.
Paul
Badness in kref_get at lib/kref.c:32
[<c01b1832>] kref_get+0x26/0x30
[<c01370fd>] ckrm_add_member+0x9d/0xc8
[<c01a7e9d>] rcfs_attr_store+0x109/0x148
[<c01a5975>] flush_write_buffer+0x2d/0x34
[<c01a59c7>] configfs_write_file+0x4b/0x70
[<c0153600>] vfs_write+0x94/0xf0
[<c0153708>] sys_write+0x40/0x6c
[<c0102d70>] syscall_call+0x7/0xb
Unable to handle kernel paging request at virtual address 00100104
printing eip:
c0135fea
*pde = 00000000
Oops: 0002 [#1]
SMP
Modules linked in: pcnet32 mii crc32 uhci_hcd rtc
CPU: 0
EIP: 0060:[<c0135fea>] Not tainted VLI
EFLAGS: 00010246 (2.6.11-smp-DEV)
EIP is at ckrm_remove_child+0x16/0x34
eax: 00100100 ebx: cf2b7880 ecx: cf2b78c4 edx: 00200200
esi: cf2b7880 edi: c0392d40 ebp: cef3e540 esp: cfea9f10
ds: 007b es: 007b ss: 0068
Process events/0 (pid: 4, threadinfo=cfea8000 task=cfedaa60)
Stack: c0392d68 c013627c cf2b7880 c013623c cf2b78b4 cef3ea50 cef3e540 c01b189d
cf2b78b4 c0392d40 cf2b7880 c0136989 cf2b78b4 c013623c c0392d74 c04ba6a0
c0392dc4 c12ad000 00000000 00000001 c0392d40 c0136a7a cef3e540 cf2b7880
Call Trace:
[<c013627c>] ckrm_release_class+0x40/0xc0
[<c01b189d>] kref_put+0x61/0x67
[<c0136989>] ckrm_setclass_internal+0x109/0x1bc
[<c0136a7a>] ckrm_setclass_wq+0x3e/0xa0
[<c012ae83>] worker_thread+0x1b3/0x240
[<c012e4f9>] kthread+0x7d/0xac
[<c0101309>] kernel_thread_helper+0x5/0xc
Code: 8b 53 4c 89 42 04 89 51 44 8d 53 4c 89 50 04 89 43 4c 5b c3 90
53 8b 5c 24 08 8d 43 4c 39 43 4c 75 23 8d 4b 44 8b 51 04 8b 43 44 <89>
50 04 89 02 c7 43 44 00 01 10 00 c7 41 04 00 02 20 00 b8 01
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