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| author | Dan Williams <dan.j.williams@intel.com> | 2014-01-29 14:05:53 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-29 16:22:40 -0800 |
| commit | 59f2e7df574c78e952d79435de3f4867349403aa (patch) | |
| tree | e03333701756e783f4a5085c8df2777651900970 /lib | |
| parent | f544e14f3e765b5241d7f234fee677506b8ce07f (diff) | |
| download | lwn-59f2e7df574c78e952d79435de3f4867349403aa.tar.gz lwn-59f2e7df574c78e952d79435de3f4867349403aa.zip | |
dma-debug: fix overlap detection
Commit 0abdd7a81b7e ("dma-debug: introduce debug_dma_assert_idle()") was
reworked to expand the overlap counter to the full range expressable by
3 tag bits, but it has a thinko in treating the overlap counter as a
pure reference count for the entry.
Instead of deleting when the reference-count drops to zero, we need to
delete when the overlap-count drops below zero. Also, when detecting
overflow we can just test the overlap-count > MAX rather than applying
special meaning to 0.
Regression report available here:
http://marc.info/?l=linux-netdev&m=139073373932386&w=2
This patch, now tested on the original net_dma case, sees the expected
handful of reports before the eventual data corruption occurs.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Cc: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/dma-debug.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/lib/dma-debug.c b/lib/dma-debug.c index c38083871f11..2defd1308b04 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -463,7 +463,7 @@ static int active_pfn_set_overlap(unsigned long pfn, int overlap) int i; if (overlap > ACTIVE_PFN_MAX_OVERLAP || overlap < 0) - return 0; + return overlap; for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--) if (overlap & 1 << i) @@ -486,7 +486,7 @@ static void active_pfn_inc_overlap(unsigned long pfn) * debug_dma_assert_idle() as the pfn may be marked idle * prematurely. */ - WARN_ONCE(overlap == 0, + WARN_ONCE(overlap > ACTIVE_PFN_MAX_OVERLAP, "DMA-API: exceeded %d overlapping mappings of pfn %lx\n", ACTIVE_PFN_MAX_OVERLAP, pfn); } @@ -517,7 +517,11 @@ static void active_pfn_remove(struct dma_debug_entry *entry) unsigned long flags; spin_lock_irqsave(&radix_lock, flags); - if (active_pfn_dec_overlap(entry->pfn) == 0) + /* since we are counting overlaps the final put of the + * entry->pfn will occur when the overlap count is 0. + * active_pfn_dec_overlap() returns -1 in that case + */ + if (active_pfn_dec_overlap(entry->pfn) < 0) radix_tree_delete(&dma_active_pfn, entry->pfn); spin_unlock_irqrestore(&radix_lock, flags); } |