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| author |   Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-14 15:22:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-08-14 15:22:43 -0700 |
| commit | 5848dc5b1b76d83599dcec1b39f188a7cbdca7e2 (patch) | |
| tree | 740d7bd1ae3c67665ff0d602e1ccfea013609264 /kernel/dma/Kconfig | |
| parent | dma-debug: fix debug_dma_assert_idle(), use rcu_read_lock() (diff) | |
| download | linux-dev-5848dc5b1b76d83599dcec1b39f188a7cbdca7e2.tar.xz linux-dev-5848dc5b1b76d83599dcec1b39f188a7cbdca7e2.zip | |
dma-debug: remove debug_dma_assert_idle() function
This remoes the code from the COW path to call debug_dma_assert_idle(),
which was added many years ago.
Google shows that it hasn't caught anything in the 6+ years we've had it
apart from a false positive, and Hugh just noticed how it had a very
unfortunate spinlock serialization in the COW path.
He fixed that issue the previous commit (a85ffd59bd36: "dma-debug: fix
debug_dma_assert_idle(), use rcu_read_lock()"), but let's see if anybody
even notices when we remove this function entirely.
NOTE! We keep the dma tracking infrastructure that was added by the
commit that introduced it. Partly to make it easier to resurrect this
debug code if we ever deside to, and partly because that tracking by pfn
and offset looks quite reasonable.
The problem with this debug code was simply that it was expensive and
didn't seem worth it, not that it was wrong per se.
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/dma/Kconfig')
| -rw-r--r-- | kernel/dma/Kconfig | 5 |
1 files changed, 0 insertions, 5 deletions
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index f4770fcfa62b..5732b2b3ef17 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -186,11 +186,6 @@ config DMA_API_DEBUG drivers like double-freeing of DMA mappings or freeing mappings that were never allocated. - 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. |