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SubjectRe: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries
On Fri, Jan 09, 2009 at 07:14:46PM +0100, Joerg Roedel (joro@8bytes.org) wrote:
> > > +static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry,
> > > + unsigned long *flags)
> > > +{
> > > + int idx = hash_fn(entry);
> > > + unsigned long __flags;
> > > +
> > > + spin_lock_irqsave(&dma_entry_hash[idx].lock, __flags);
> > > + *flags = __flags;
> > > + return &dma_entry_hash[idx];
> > > +}
> > > +
> > > +/*
> > > + * Give up exclusive access to the hash bucket
> > > + */
> > > +static void put_hash_bucket(struct hash_bucket *bucket,
> > > + unsigned long *flags)
> > > +{
> > > + unsigned long __flags = *flags;
> > > +
> > > + spin_unlock_irqrestore(&bucket->lock, __flags);
> > > +}
> >
> > Why do you need such ugly helpers?
>
> Because everything else I thought about here was even more ugly. But
> maybe you have a better idea? I tried to lock directly in the debug_
> functions. But this is ugly and unnecessary code duplication.

I believe that having direct locking in the debug_ functions is not a
duplication, anyone will have a direct vision on the locking and hash
array dereference, and this will be just one additional line compared to
the get_* call and the same number of lines for the put :)

--
Evgeniy Polyakov


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