On Wed, Oct 31, 2012 at 05:35:46PM +0000, Christoph Lameter wrote:
> On Wed, 31 Oct 2012, Shan Wei wrote:
>
> > -
> > list_for_each_entry(pos, &ipcomp_tfms_list, list) {
> > struct crypto_comp *tfm;
> >
> > tfms = pos->tfms;
> > - tfm = *per_cpu_ptr(tfms, cpu);
> > +
> > + /* This can be any valid CPU ID so we don't need locking. */
> > + tfm = *this_cpu_ptr(tfms);
>
> It would be better to use
>
> this_cpu_read(tfms)
>
> since that would also make it atomic vs interrupts. The above code (both
> original and modified) could determine a pointer to a per cpu structure
> and then take an interrupt which would move the task. On return we would
> be accessing the per cpu variable of another processor.
Please refer to the comment in the patch above.
But I think the patch is wrong anyway because it would introduce
a warning, no?
Thanks,
--
Email: Herbert Xu <herb...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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