Messages in this thread | | | Date | Tue, 16 Jun 2009 10:14:28 +0200 | From | Joerg Roedel <> | Subject | Re: dma-debug: check_for_stack background? |
| |
On Tue, Jun 16, 2009 at 03:16:37PM +0900, FUJITA Tomonori wrote: > On Mon, 15 Jun 2009 10:13:55 +0200 > Joerg Roedel <joerg.roedel@amd.com> wrote: > > > On Sun, Jun 14, 2009 at 11:43:42PM +0200, Stefan Richter wrote: > > > Ben Dooks wrote: > > >> On Sun, Jun 14, 2009 at 08:56:29PM +0200, Stefan Richter wrote: > > >>> the DMA debug facility warns about mappings of on-stack memory. > > >>> What's the problem with that? > > > ... > > >> I'm not sure if it is possible on all architectures, however the > > >> DMA mapping documentation prohibts the use of stack memory. > > > > > > Ah, it has all been documented in plain sight for ages. Thanks for the > > > pointer. > > > > Problem is that the stack might go away or could be otherwise reused > > while the DMA is in-flight. This could cause really hard to debug > > problems. > > Not true. Even if you use the stack buffer for DMA synchronously, it > doesn't work (we had the bad code like starting dma and waiting for > the completion).
I've not written that this is the only problem. I know that there may be others like the one you experienced. But what I wrote could also happen and is a problem :)
Joerg
-- | Advanced Micro Devices GmbH Operating | Karl-Hammerschmidt-Str. 34, 85609 Dornach bei München System | Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München | Registergericht München, HRB Nr. 43632
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |