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authorDan Williams <dan.j.williams@intel.com>2014-01-29 22:05:53 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-30 00:22:40 (GMT)
commit59f2e7df574c78e952d79435de3f4867349403aa (patch)
treee03333701756e783f4a5085c8df2777651900970 /lib/dma-debug.c
parentf544e14f3e765b5241d7f234fee677506b8ce07f (diff)
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/dma-debug.c')
-rw-r--r--lib/dma-debug.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index c380838..2defd13 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);
}

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