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SubjectRe: Bug: "bad unlock balance detected" 2.6.27-rc3-next-20080820
Vegard Nossum wrote:
> On Thu, Aug 21, 2008 at 9:04 AM, jay kumar <jaykumarks@gmail.com> wrote:
>> While testing 2.6.27-rc3-next-20080820 , i observed this "BUG:bad
>> unlock balance detected" during boot time
>>
>> commit 765d4840cc9cca98c0cc4ff4764608780c3265f6
>> Author: Stephen Rothwell <sfr@canb.auug.org.au>
>> Date: Wed Aug 20 18:59:47 2008 +1000
>>
>>
>> Bug info:
>>
>> [ 0.140173] =====================================
>> [ 0.145977] [ BUG: bad unlock balance detected! ]
>> [ 0.145977] -------------------------------------
>> [ 0.145977] khelper/12 is trying to release lock (&p->cred_exec_mutex) at:
>> [ 0.146977] [<c05c624f>] mutex_unlock+0xd/0xf
>> [ 0.146977] but there are no more locks to release!
>> [ 0.146977]
>> [ 0.146977] other info that might help us debug this:
>> [ 0.146977] no locks held by khelper/12.
>> [ 0.146977]
>> [ 0.146977] stack backtrace:
>> [ 0.146977] Pid: 12, comm: khelper Not tainted 2.6.27-rc3-next-20080820 #13
>> [ 0.146977] [<c05c624f>] ? mutex_unlock+0xd/0xf
>> [ 0.146977] [<c0242944>] print_unlock_inbalance_bug+0xa5/0xb2
>> [ 0.146977] [<c05c624f>] ? mutex_unlock+0xd/0xf
>> [ 0.146977] [<c0245cd7>] lock_release+0x8f/0x186
>> [ 0.146977] [<c05c61f0>] __mutex_unlock_slowpath+0x9b/0xed
>> [ 0.146977] [<c05c624f>] mutex_unlock+0xd/0xf
>> [ 0.146977] [<c029506f>] free_bprm+0x24/0x39
>> [ 0.146977] [<c029644e>] do_execve+0x1e5/0x1fb
>> [ 0.146977] [<c0202156>] sys_execve+0x2e/0x51
>> [ 0.146977] [<c0203a72>] syscall_call+0x7/0xb
>> [ 0.146977] [<c0206654>] ? kernel_execve+0x1c/0x21
>> [ 0.146977] [<c023383c>] ? ____call_usermodehelper+0x0/0x129
>> [ 0.146977] [<c023395b>] ? ____call_usermodehelper+0x11f/0x129
>> [ 0.146977] [<c023383c>] ? ____call_usermodehelper+0x0/0x129
>> [ 0.146977] [<c020466b>] ? kernel_thread_helper+0x7/0x10
>> [ 0.146977] =======================
>
> (config clipped)
>
> Hi,
>
> Thanks for the report. The error comes from
>
> commit d9a939fb80ef390b78b3c801f668bd1e35ebc970
> Author: David Howells <dhowells@redhat.com>
> Date: Thu Aug 7 20:02:20 2008 +1000
>
> CRED: Make execve() take advantage of copy-on-write credentials
>
> (Added to Cc. I guess it's also nice to Cc linux-next on errors in -next code.)
>
> I couldn't reproduce your original failure, but I've attempted to fix
> it by reordering the mutex unlock and bprm free and removing the
> extraneous unlock (see attached patch; it boots for me without
> errors).
>
>
> Vegard
>
Hi,

Thanks, the patch fixes the "bad unlock balance" warning I was hitting
with the next-20080821 patchset.

Tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>

--
Thanks & Regards,
Kamalesh Babulal,
Linux Technology Center,
IBM, ISTL.


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