On Thu, Jul 9, 2009 at 4:36 PM, Tirumala Reddy Marri<tmarri@xxxxxxxx> wrote:
> Hi Dan,
> While I was debugging file system crash with AMCC ADMA driver , I
> noticed that async_tx_clear_ack() never been called. Where is the
> async_tx->flags is cleared up on completion of DMA transfer ? Looks like
> this not cleared and I am hitting the BUG_ON() in async_tx_submit(). If
> I call async_tx_clear_ack() in ppc4xx_ adma_free_slots() function
> everything seems working fine .
>
> This doesn't sound normal something is going on. Somehow descriptors are
> allocated even though they are not free .
>
If you take a look at iop-adma.c you will see lines like:
sw_desc->async_tx.flags = flags;
So we inheret the DMA_CTRL_ACK flag from when async_tx calls the
->prep routine. It is not important to clear ack on completion, it is
only important to reset it at prep time. It is merely a flag that
holds off recycling descriptors while the api may still want to attach
a dependency.
If memory serves correctly we have tried to debug this driver before,
please refresh my memory on how this driver is different than the one
produced by Emcraft[1] that does not seem to exhibit these problems?
Thanks,
Dan
[1]: http://patchwork.ozlabs.org/patch/18116/
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