linux-kernel - Re: [PATCH 03/16] dma-debug: add hash functions for dma_debug

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Message-ID: <20090109181446.GB9466@8bytes.org>
Date:	Fri, 9 Jan 2009 19:14:46 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	Joerg Roedel <joerg.roedel@....com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	mingo@...hat.com
Subject: Re: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries

On Fri, Jan 09, 2009 at 08:55:42PM +0300, Evgeniy Polyakov wrote:
> Hi Joerg.
> 
> On Fri, Jan 09, 2009 at 05:19:17PM +0100, Joerg Roedel (joerg.roedel@....com) wrote:
> > +/*
> > + * Request exclusive access to a hash bucket for a given dma_debug_entry.
> > + */
> > +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.

> 
> > + * Add an entry to a hash bucket
> > + */
> > +static void hash_bucket_add(struct hash_bucket *bucket,
> > +			    struct dma_debug_entry *entry)
> > +{
> > +	list_add_tail(&entry->list, &bucket->list);
> > +}
> 
> > +/*
> > + * Remove entry from a hash bucket list
> > + */
> > +static void hash_bucket_del(struct dma_debug_entry *entry)
> > +{
> > +	list_del(&entry->list);
> > +}
> 
> Do you really need this getting they are called only from single place?

Hmm, true. I will inline these functions.

Joerg
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