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authorDan Williams <dan.j.williams@intel.com>2014-01-22 03:48:12 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-22 04:19:41 +0400
commit0abdd7a81b7e3fd781d7fabcca49501852bba17e (patch)
tree20ab3aa4b476ceaf6d3a824c842cd581445ded8b /lib/Kconfig.debug
parent03d11a0e458d7008192585124e4c3313c2829046 (diff)
downloadlinux-0abdd7a81b7e3fd781d7fabcca49501852bba17e.tar.xz
dma-debug: introduce debug_dma_assert_idle()
Record actively mapped pages and provide an api for asserting a given page is dma inactive before execution proceeds. Placing debug_dma_assert_idle() in cow_user_page() flagged the violation of the dma-api in the NET_DMA implementation (see commit 77873803363c "net_dma: mark broken"). The implementation includes the capability to count, in a limited way, repeat mappings of the same page that occur without an intervening unmap. This 'overlap' counter is limited to the few bits of tag space in a radix tree. This mechanism is added to mitigate false negative cases where, for example, a page is dma mapped twice and debug_dma_assert_idle() is called after the page is un-mapped once. Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Joerg Roedel <joro@8bytes.org> Cc: Vinod Koul <vinod.koul@intel.com> Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: James Bottomley <JBottomley@Parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/Kconfig.debug')
-rw-r--r--lib/Kconfig.debug12
1 files changed, 10 insertions, 2 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 6982094a7e74..900b63c1e899 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1584,8 +1584,16 @@ config DMA_API_DEBUG
With this option you will be able to detect common bugs in device
drivers like double-freeing of DMA mappings or freeing mappings that
were never allocated.
- This option causes a performance degredation. Use only if you want
- to debug device drivers. If unsure, say N.
+
+ This also attempts to catch cases where a page owned by DMA is
+ accessed by the cpu in a way that could cause data corruption. For
+ example, this enables cow_user_page() to check that the source page is
+ not undergoing DMA.
+
+ This option causes a performance degradation. Use only if you want to
+ debug device drivers and dma interactions.
+
+ If unsure, say N.
source "samples/Kconfig"