[ipc] 5769cf63: LTP semget02 TFAILs

[Fengguang Wu <fengguang.wu@intel.com>]

Hi Davidlohr,

We noticed LTP test failures

        ltp.msgget02.1.TFAIL
        ltp.semget02.2.TFAIL
        ltp.semget02.3.TFAIL

and the first bad commit is

commit 5769cf6355d87f63906b3e51887eff7017c39217
Author:     Davidlohr Bueso <davidlohr@hp.com>
AuthorDate: Wed Jan 15 16:56:01 2014 +1100
Commit:     Stephen Rothwell <sfr@canb.auug.org.au>
CommitDate: Wed Jan 15 16:56:01 2014 +1100

    ipc: share ids rwsem when possible in ipcget_public
    
    ...  and rewrite the function.  For scenarios where the key is found and
    we end up just doing different routinary checks, we can downgrade the
    ids->rwsem and share it among concurrent readers.  These checks include
    the following, which are all safe to share the lock:
    
    ops->more_checks() >>  sem_more_checks(), shm_more_checks()
    ipc_check_perms()  >>  ipcperms(),ops->associate() >> [lsm]_[ipctype]_associate()
    
    Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
    Cc: Aswin Chandramouleeswaran <aswin@hp.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Manfred Spraul <manfred@colorfullife.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 ipc/util.c | 60 +++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 33 insertions(+), 27 deletions(-)

Thanks,
Fengguang