Re: panic in bus_dma_tag_destroy()
On Wed, Oct 06, 2004 at 04:00:06PM -0700, Matthew Dillon wrote:
>
> :I'm seeing a panic in bus_dma_tag_destroy() on the free of
> :dmat->segments. In comparing this to FBSD 4.10 and 5.x, the code seems
> :closest to the 5.x branch with the exception that 5.x seems to defer
> :the allocation of segments til bus_dmamap_create() while DFly
> :allocates this in bus_dma_tag_create(). The only other thing I noticed
> :was that DFly allocates segments with M_INTWAIT while FBSD allocates
> :it with M_NOWAIT.
>
> Get a backtrace from the DDB prompt. The 'trace' command. If you
> aren't getting a DDB prompt then compile up a kernel with 'options DDB'
> in the kernel config.
ok, I'll need to hook up a console.
> You didn't mention which driver was faililng, but the backtrace should
> show that.
it's a new one I'm working on.
> In anycase, if I understand your analysis the driver must be calling
> bus_dma_tag_destroy() with a NULL svd->parent_dmat. I will analyize
> the driver and determine whether it is appropriate to have
> bus_dma_tag_destroy() check for NULL or whether it is appropriate for
> the driver to check for NULL and not call bus_dma_tag_destroy().
I'm pretty sure svd->parent_dmat is not NULL after allocation. The
call to bus_dma_tag_create() doesn't return an error in any case.
Commenting out lines 235-236 of src/sys/i386/i386/busdma_machdep.c
makes the panic go away for me.
--
Chuck Tuffli <chuck_tuffli@agilent.com>
Agilent Technologies, Storage Area Networking
(916) 788 5086
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