Greetings,

I got the below dmesg and the first bad commit is

commit c5d0282a0405b0a81fa3390e4230e4cbb3ced7a2
Author: Davidlohr Bueso <davidlohr.bueso@hp.com>
Date:   Fri Jul 19 09:56:58 2013 +1000

    ipc,shm: shorten critical region for shmat
    
    Similar to other system calls, acquire the kern_ipc_perm lock after doing
    the initial permission and security checks.
    
    Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
    Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Manfred Spraul <manfred@colorfullife.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

[   20.702156] 
[   20.702493] ================================================
[   20.703511] [ BUG: lock held when returning to user space! ]
[   20.704532] 3.11.0-rc1-next-20130719 #50 Not tainted
[   20.705416] ------------------------------------------------
[   20.706425] trinity-child0/174 is leaving the kernel with locks still held!
[   20.707638] 1 lock held by trinity-child0/174:
[   20.708475]  #0:  (rcu_read_lock){.+.+..}, at: [<ffffffff814a8491>] do_shmat+0xe1/0x500

git bisect start c1f631b9a68251007a6353041ae90f9f7dca771c d03792f9db9b892f494d3aa19d767ddf0365d1ff --
git bisect good 10a3f1f902465ae1320cc95a3284fd3697e05dd8  # 11:14     65+  binfmt_elf.c: use get_random_int() to fix entropy depleting
git bisect  bad dac28788378838efb63e37a7eabd7729d97aba6b  # 11:32      0-  dcache: remove dentries from LRU before putting on dispose list
git bisect good 3140b2ed6dfe5c9e5eca371c77ca85dca05321d4  # 11:50     65+  ipc,shm: introduce shmctl_nolock
git bisect  bad 48a91248649fa3327bd8a31c114ee9149a07f3a7  # 12:04      0-  staging/lustre/ldlm: convert to shrinkers to count/scan API
git bisect good 98b78126a51aa5d3ee6d5dae5768e0d16deeeaa3  # 12:14     65+  ipc,shm: cleanup do_shmat pasta
git bisect  bad 36ccfd799cad33e2edd5c14ac8776b33e63d195b  # 12:14      0-  ipc: rename ids->rw_mutex
git bisect  bad c5d0282a0405b0a81fa3390e4230e4cbb3ced7a2  # 12:14      0-  ipc,shm: shorten critical region for shmat
git bisect good 98b78126a51aa5d3ee6d5dae5768e0d16deeeaa3  # 15:34    195+  ipc,shm: cleanup do_shmat pasta
git bisect  bad c1f631b9a68251007a6353041ae90f9f7dca771c  # 15:34      0-  Add linux-next specific files for 20130719
git bisect good 709b465ee655387c4ec056383fa27f16c64f48db  # 18:21    195+  Revert "ipc,shm: shorten critical region for shmat"
git bisect good d471ce53b1fab60110e4e9f647a345cea31752de  # 18:44    195+  Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml
git bisect  bad c1f631b9a68251007a6353041ae90f9f7dca771c  # 18:44      0-  Add linux-next specific files for 20130719

Thanks,
Fengguang