Re: [PATCH 2/2] clk: Move init fields from clk to clk_hw

[Turquette, Mike]

On Wed, Apr 11, 2012 at 12:57 PM, Saravana Kannan
<skannan@xxxxxxxxxxxxxx> wrote:
> On 04/11/2012 10:59 AM, Turquette, Mike wrote:
>> On Thu, Apr 5, 2012 at 6:30 PM, Saravana Kannan<skannan@xxxxxxxxxxxxxx>
>> My only concern with this series is that platform clock code will
>> access struct clk_hw members without the appropriate lock held (namely
>> prepare_lock).  I'm a bit worried that there might be a case where
>> some clock code access clk_hw->name when clk_hw has somehow been
>> destroyed/altered (e.g. if clk_put every finally gets implemented...).
>>  Besides clk_put are there any real instances where this might happen?
>
> This problem is true for any struct/field marked as __init_data. So, I don't
> think this is a real problem. If someone is stupid enough to mark their data
> as __init_data and access them later, then there is not much we can do.
> Also, I believe the compiler throws out some warning when you try to access
> __init_data from non-init code.

I'm referring to platform clock code accessing clk_hw->name or
clk_hw->parent_names AFTER the core code has copied the initialization
data.  So this isn't an __initdata problem as much as it is a design
issue with exposing some members of struct clk_hw.  I think that this
is basically OK since the benefits of not having to use so many
helpers functions in platform clock code is obvious and if a platform
gets bitten by this then they will learn the hard way to honor the
locking semantics outlined in Documentation/clk.txt

>> I'll be pushing my fixes branch out to the list soon.  Do you want to
>> rebase this change on top of it taking into account the __initdata
>> bits?
>
> I thought it might be easier for you to base your changes on top of my
> patch. But I can try to rebase mine on top of your changes. Hopefully your
> fixes aren't crazy big/complex.

I don't think the fixes are a big deal, especially in the core code.

> This is a busy week for me at work. I will try to send a patch in a day or
> two.

OK.  I might take a swing at it myself if I have time.

Regards,
Mike
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