On 2016-04-06 09:38 AM, James Bottomley wrote:
> On Wed, 2016-04-06 at 09:21 -0400, Bastien Philbert wrote:
>>
>> On 2016-04-06 03:48 AM, Julian Calaby wrote:
>>> Hi Bastien,
>>>
>>> On Wed, Apr 6, 2016 at 7:19 AM, Bastien Philbert
>>> <bastienphilb...@gmail.com> wrote:
>>>> This fixes backwards locking in the function __csio_unreg_rnode
>>>> to
>>>> properly lock before the call to the function csio_unreg_rnode
>>>> and
>>>> not unlock with spin_unlock_irq as this would not allow the
>>>> proper
>>>> protection for concurrent access on the shared csio_hw structure
>>>> pointer hw. In addition switch the locking after the critical
>>>> region
>>>> function call to properly unlock instead with spin_unlock_irq on
>>>>
>>>> Signed-off-by: Bastien Philbert <bastienphilb...@gmail.com>
>>>> ---
>>>> drivers/scsi/csiostor/csio_rnode.c | 4 ++--
>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/scsi/csiostor/csio_rnode.c
>>>> b/drivers/scsi/csiostor/csio_rnode.c
>>>> index e9c3b04..029a09e 100644
>>>> --- a/drivers/scsi/csiostor/csio_rnode.c
>>>> +++ b/drivers/scsi/csiostor/csio_rnode.c
>>>> @@ -580,9 +580,9 @@ __csio_unreg_rnode(struct csio_rnode *rn)
>>>> ln->last_scan_ntgts--;
>>>> }
>>>>
>>>> - spin_unlock_irq(&hw->lock);
>>>> - csio_unreg_rnode(rn);
>>>> spin_lock_irq(&hw->lock);
>>>> + csio_unreg_rnode(rn);
>>>> + spin_unlock_irq(&hw->lock);
>>>
>>> Are you _certain_ this is correct? This construct usually appears
>>> when
>>> a function has a particular lock held, then needs to unlock it to
>>> call
>>> some other function. Are you _certain_ that this isn't the case?
>>>
>>> Thanks,
>>>
>> Yes I am pretty certain this is correct. I checked the paths that
>> called this function
>> and it was weired that none of them gradded the spinlock before hand.
>
> That's not good enough. If your theory is correct, lockdep should be
> dropping an already unlocked assertion in this codepath ... do you see
> this?
>
> James
>
>
Yes I do. For now just drop the patch but I am still concerned that we are
double unlocking here.
Bastien
>
>
