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

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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@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


.






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