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SubjectRe: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries
On Wed, 14 Jan 2009 12:43:47 +0100 Ingo Molnar <mingo@elte.hu> wrote:

>
> * Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > On Fri, 9 Jan 2009 17:19:17 +0100 Joerg Roedel <joerg.roedel@amd.com> wrote:
> >
> > > +struct hash_bucket {
> > > + struct list_head list;
> > > + spinlock_t lock;
> > > +} ____cacheline_aligned;
> >
> > __cacheline_aligned_in_smp.
> >
> > This all looks like an exotically large amount of code for a debug
> > thingy?
>
> this code checks the DMA usage of ~1 million lines of kernel code - all
> the DMA using drivers. I think Joerg's feature is hugely relevant as DMA
> scribbles are one of the hardest to debug kernel bugs: they can end up in
> permanent data corruption or other hard to find bugs. In fact i think his
> patchset is rather simple and even having 10 times as much debug code
> would pay for its existence in the long run.
>

Have we previously found bugs by other means which this facility would
have detected? I don't recall any...



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