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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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