Re: [PATCH] PM / wakeirq: Add wakeup name to dedicated wake irqs

[Andy Shevchenko]

On Fri, Feb 16, 2018 at 12:54 PM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> On Fri, Feb 16, 2018 at 11:39 AM, Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:
>> On Fri, Feb 16, 2018 at 11:14 AM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>>> On Wed, Feb 14, 2018 at 12:23 PM, Andy Shevchenko
>>> <andy.shevchenko@xxxxxxxxx> wrote:

>>> IMO it is somewhat excessive to put the entire sprintf() under a raw
>>> spinlock and it's not even necessary.
>>
>> It's a copy'n'paste of from the rest of functions there.
>
> Fair enough. :-)

>>> The value can change any time after you've dropped the lock and in
>>> particular before the function returns, so why bother with locking?
>>> desc will not go away from under you at that point anyway.
>>
>> IIRC descriptor's content might be changed, or descriptor itself might
>> be gone (potential crash).
>
> No, desc cannot go away at this point AFAICS due to the kernfs
> refcounting.  And the lock is *inside* of the desc object anyway, so
> it doesn't help really against that.

Oh, indeed.

> The contents may change, but so what?
>
> Effectively, you read an int and reading an int is atomic.  It may
> change after that, but the lock doesn't prevent it from changing.  It
> only prevents the change from being applied to it before you drop the
> lock, but why do you care?

So, with explanations above, perhaps we can produce the patch to
remove those locks from the rest?

-- 
With Best Regards,
Andy Shevchenko