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| author | Dan Williams <dan.j.williams@intel.com> | 2014-01-21 15:48:12 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-21 16:19:41 -0800 |
| commit | 0abdd7a81b7e3fd781d7fabcca49501852bba17e (patch) | |
| tree | 20ab3aa4b476ceaf6d3a824c842cd581445ded8b /lib/Kconfig.debug | |
| parent | 03d11a0e458d7008192585124e4c3313c2829046 (diff) | |
| download | lwn-0abdd7a81b7e3fd781d7fabcca49501852bba17e.tar.gz lwn-0abdd7a81b7e3fd781d7fabcca49501852bba17e.zip | |
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.debug | 12 |
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" |