Re: [PATCH v2] ath10k: add SoC power save option to PCI features map

[Kalle Valo <kvalo@qca.qualcomm.com>]

Michal Kazior <michal.kazior@tieto.com> writes:

> On 2 August 2013 09:58, Bartosz Markowski <bartosz.markowski@tieto.com> wrote:
>> Unify the PCI options location.
>>
>> By default the SoC PS option is disabled to boost the
>> performance and due to poor stability on early HW revisions.
>> In future we can remove the module parameter and turn on/off
>> the PS for given hardware.
>>
>> This change also makes the pci module parameter for SoC PS static.
>>
>> Signed-off-by: Bartosz Markowski <bartosz.markowski@tieto.com>
>
> Hmm.. I'm worried about pci wake/sleep locking:
>
>  (a) pci_wake() (awake count =1)
>  (a) do something
>  Now, if pci_sleep() and pci_wake() happen simultaneously/are
> preempted splitting primitive operations to:
>  (a) pci_sleep(): decrease awake count (=0)
>  (b) pci_wake(): increase awake count (=1), iowrite, wait for awake, return
>  (a) pci_sleep(): iowrite(). return
>  The flow in (b) now thinks the device is awake, but it's not
> guaranteed to be anymore because it has been put to sleep by (a).

Yeah, there's a race alright. I wonder if I have ever seen a proper use
of a atomic variable in a wireless driver :)

But this doesn't prevent taking this patch as the race has existed since
the beginning, right?

-- 
Kalle Valo