Re: [PATCH v5 03/23] scsi: hisi_sas: optimise the usage of hisi_hba.lock

[John Garry]

On 12/06/2017 10:45, Arnd Bergmann wrote:
> On Mon, Jun 12, 2017 at 10:26 AM, John Garry <john.garry@xxxxxxxxxx> wrote:
> > On 10/06/2017 21:44, kbuild test robot wrote:
> >
> >
> > I don't think that reusing flags variable is in error, as there would be no
> > nested spinlock at this point within the function.
> >
> > If it is not recommended or not permitted to reuse flags variable for
> > separate spinlocks, then that can be changed - I don't know.
>
> No, look again: coccinelle is right as the locks are nested in
> https://github.com/0day-ci/linux/blob/bf95e9cccde4af4ed2012a6ec44d48b545d5ffed/drivers/scsi/hisi_sas/hisi_sas_main.c#L1208
>
> dq->lock is already held and you acquire task->task_state_lock in
> line 1208, which overwrites the flags.
>
>       Arnd

Hi Arnd,

Ah, now I see. The error message mislead me, as I straight away checked 
hisi_sas_task_prep() which does the same locking and also reuses flags 
for spinlock_irqsave(), but it's safe here.

But, as you pointed out, the problem is in 
hisi_sas_internal_abort_task_exec().

A thought: it would be useful if coccinelle printed explicitly the 
function name which has the warning/error.

Thanks,
John

> .