[PATCH] dma-debug: disable DMA_API_DEBUG for now

FUJITA Tomonori
2009-06-05T08:33:43Z

dma-debugs wrongly assumes that no multiple DMA transfers are
performed against the same dma address on one device at the same
time. However it's true only with hardware IOMMUs. For example, an
application can easily send the same buffer twice with different
lengths to one device by using DIO and AIO. If these requests are not
unmapped in the same order in which they were mapped,
hash_bucket_find() finds a wrong entry and gives a false warning.

We should fix this before 2.6.30 release. Seems that there is no
easy way to fix it. I think that it's better to just disable
dma-debug for now.

Torsten Kaiser found this bug with the RAID1 configuration:

http://marc.info/?t=124336541900008&r=1&w=2

Reported-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
arch/sh/Kconfig | 1 -
arch/x86/Kconfig | 1 -
2 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index e7390dd..4fb19d7 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -14,7 +14,6 @@ config SUPERH
select HAVE_GENERIC_DMA_COHERENT
select HAVE_IOREMAP_PROT if MMU
select HAVE_ARCH_TRACEHOOK
- select HAVE_DMA_API_DEBUG
help
The SuperH is a RISC processor targeted for use in embedded systems
and consumer electronics; it was also used in the Sega Dreamcast
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a6efe0a..b3cf490 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -42,7 +42,6 @@ config X86
select HAVE_GENERIC_DMA_COHERENT if X86_32
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select USER_STACKTRACE_SUPPORT
- select HAVE_DMA_API_DEBUG
select HAVE_KERNEL_GZIP
select HAVE_KERNEL_BZIP2
select HAVE_KERNEL_LZMA
--
1.6.0.6