Re: [PATCH] usbnet: Fix two races between usbnet_stop() and the BH

From: Oliver Neukum
Date: Tue Aug 25 2015 - 08:38:01 EST

On Mon, 2015-08-24 at 14:21 -0400, Alan Stern wrote:
> > In theory, an architecture could implement atomic bit operations
> using
> > a spinlock to insure atomicity. I don't know if any architectures
> do
> > this, but if they do then the scenario above could arise.
> Now that I see this in writing, I realize it's not possible after
> all.
> clear_bit() et al. will work with a single unsigned long, which
> doesn't
> leave any place for spinlocks or other mechanisms. I was thinking of
> atomic_t.

Refuting yourself you are making the assumption that the lock has
to be inside the data structure. That is not true.


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