linux-kernel - Re: [Lf_driver_backport] [PATCH 2/4] compat: backport work

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Message-ID: <CAJdJm_MD1QQG3hyQmo-RffeObGBSViLAOBZeyRJqoEbh0x2PMA@mail.gmail.com>
Date:	Tue, 20 Mar 2012 10:29:33 -0400
From:	Anderson Lizardo <anderson.lizardo@...nbossa.org>
To:	"Luis R. Rodriguez" <mcgrof@...jolero.org>
Cc:	Johannes Berg <johannes@...solutions.net>,
	lf_driver_backport@...ts.linux-foundation.org,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andre Guedes <andre.guedes@...nbossa.org>
Subject: Re: [Lf_driver_backport] [PATCH 2/4] compat: backport work_busy()

Hi Luiz,

[I'm subscribed only to lf_driver_backport]

On Tue, Mar 20, 2012 at 9:50 AM, Luis R. Rodriguez <mcgrof@...jolero.org> wrote:
> On Tue, Mar 20, 2012 at 5:07 AM, Johannes Berg
> <johannes@...solutions.net> wrote:
>> On Mon, 2012-03-19 at 20:26 -0700, Luis R. Rodriguez wrote:
>>> From: "Luis R. Rodriguez" <mcgrof@...jolero.org>
>>>
>>> Best we can do is just tell the users of we are WORK_BUSY_PENDING
>>> for older kernels. The ckmake log:
>>
>> [...]
>>
>>> + * Test whether @work is currently pending or running.  There is no
>>> + * synchronization around this function and the test result is
>>> + * unreliable and only useful as advisory hints or for debugging.
>>> + * Especially for reentrant wqs, the pending state might hide the
>>> + * running state.
>>
>> What's this needed for? It seems if it's used only for hints/debugging
>> we should not need the function, or possibly simply return some
>> pointless combination like -1?
>
> net/bluetooth/hci_core.c:1701:  if (work_busy(&hdev->le_scan))

Did you consider making this change bluetooth specific (e.g. under
patches/16-bluetooth.patch with LINUX_VERSION_CODE check) so that
work_pending() is used on this location for older kernels? Or are
there other users for work_busy() besides bluetooth?

I talked with the author of this code (CC'd) and he said it should be
safe to make this replacement.

Another change I made sometime ago (specifically to bluetooth code)
for it to build with older kenels (2.6.32 in my case), was to change
this line in net/bluetooth/hci_core.c:

queue_work(system_long_wq, &hdev->le_scan);

to:

schedule_work(&hdev->le_scan);

Again, I checked with the original author and we believe it is okay to
do this (I also lightly tested these changes).

Hope that helps. Best Regards,
-- 
Anderson Lizardo
Instituto Nokia de Tecnologia - INdT
Manaus - Brazil
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