Messages in this thread | | | Subject | Re: Several races in "usbnet" module (kernel 4.1.x) | From | Oliver Neukum <> | Date | Thu, 23 Jul 2015 11:15:52 +0200 |
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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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