[PATCH regression] dma-debug: fix overlap detection
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From: Dan Williams <hidden>
Date: 2014-01-29 03:00:57
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lkml
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
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. Cc: Francois Romieu <romieu@fr.zoreil.com> Reported-by: Sander Eikelenboom <redacted> Signed-off-by: Dan Williams <redacted> --- 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. 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); }