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dma-debug: introduce debug_dma_assert_idle()

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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 7787380336 "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>
This commit is contained in:
Dan Williams 2014-01-21 15:48:12 -08:00 • committed by Linus Torvalds
parent 03d11a0e45
commit 0abdd7a81b
4 changed files with 199 additions and 15 deletions
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6
include/linux/dma-debug.h
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@ -85,6 +85,8 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,
extern void debug_dma_dump_mappings(struct device *dev);
extern void debug_dma_assert_idle(struct page *page);
#else /* CONFIG_DMA_API_DEBUG */
static inline void dma_debug_add_bus(struct bus_type *bus)
@ -183,6 +185,10 @@ static inline void debug_dma_dump_mappings(struct device *dev)
{
}
static inline void debug_dma_assert_idle(struct page *page)
{
}
#endif /* CONFIG_DMA_API_DEBUG */
#endif /* __DMA_DEBUG_H */