On Wed, 2015-07-22 at 21:33 +0300, Eugene Shatokhin wrote:
> The following part is not necessary, I think. usbnet_bh() does not
> touch
> EVENT_NO_RUNTIME_PM bit explicitly and these bit operations are
> atomic
> w.r.t. each other.
>
> > + mpn |= !test_and_clear_bit(EVENT_NO_RUNTIME_PM, &dev->flags);
> > + /* in case the bh reset a flag */
Yes, they are atomic w.r.t. each other. And that limitation worries me.
I am considering architectures which do atomic operations with
spinlocks. And this code mixes another operation into it. Can
this happen?
CPU A CPU B
take lock
read old value
set value to 0
clear bit
write back changed value
release lock
Regards
Oliver
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