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Subject: Re: [PATCH v5 03/23] scsi: hisi_sas: optimise the usage of
 hisi_hba.lock
To: Arnd Bergmann <arnd@arndb.de>
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From: John Garry <john.garry@huawei.com>
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Date: Mon, 12 Jun 2017 11:24:45 +0100
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On 12/06/2017 10:45, Arnd Bergmann wrote:
> On Mon, Jun 12, 2017 at 10:26 AM, John Garry <john.garry@huawei.com> 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

>
> .
>