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SubjectRe: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries

* 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.

Ingo


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