[dpdk-dev] [PATCH v2] ivshmem: avoid infinite loop when concatenating adjacent segments

[Anatoly Burakov <anatoly.burakov@intel.com>]

This patch aligns the logic used to check for the presence of
adjacent segments in has_adjacent_segments() with the logic used
in cleanup_segments() when actually deciding to concatenate or
not a pair of segments. Additionally, adjacent segments are
no longer considered overlapping to avoid generating errors for
segments that can happily coexist together.

This fixes an infinite loop that happened when segments where
adjacent in their physical or virtual addresses but not in their
ioremap addresses: has_adjacent_segments() reported the presence
of adjacent segments while cleanup_segments() was not considering
them for concatenation, resulting in an infinite loop since the
result of has_adjacent_segments() is used in the decision to
continue looping in cleanup_segments().

Signed-off-by: David Verbeiren <david.verbeiren@intel.com>
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_ivshmem.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_ivshmem.c b/lib/librte_eal/linuxapp/eal/eal_ivshmem.c
index 28ddf09..07aec69 100644
--- a/lib/librte_eal/linuxapp/eal/eal_ivshmem.c
+++ b/lib/librte_eal/linuxapp/eal/eal_ivshmem.c
@@ -184,21 +184,21 @@ overlap(const struct rte_memzone * mz1, const struct rte_memzone * mz2)
 	i_end2 = mz2->ioremap_addr + mz2->len;
 
 	/* check for overlap in virtual addresses */
-	if (start1 >= start2 && start1 < end2)
+	if (start1 > start2 && start1 < end2)
 		result |= VIRT;
 	if (start2 >= start1 && start2 < end1)
 		result |= VIRT;
 
 	/* check for overlap in physical addresses */
-	if (p_start1 >= p_start2 && p_start1 < p_end2)
+	if (p_start1 > p_start2 && p_start1 < p_end2)
 		result |= PHYS;
-	if (p_start2 >= p_start1 && p_start2 < p_end1)
+	if (p_start2 > p_start1 && p_start2 < p_end1)
 		result |= PHYS;
 
 	/* check for overlap in ioremap addresses */
-	if (i_start1 >= i_start2 && i_start1 < i_end2)
+	if (i_start1 > i_start2 && i_start1 < i_end2)
 		result |= IOREMAP;
-	if (i_start2 >= i_start1 && i_start2 < i_end1)
+	if (i_start2 > i_start1 && i_start2 < i_end1)
 		result |= IOREMAP;
 
 	return result;
@@ -254,17 +254,14 @@ adjacent(const struct rte_memzone * mz1, const struct rte_memzone * mz2)
 static int
 has_adjacent_segments(struct ivshmem_segment * ms, int len)
 {
-	int i, j, a;
+	int i, j;
 
 	for (i = 0; i < len; i++)
 		for (j = i + 1; j < len; j++) {
-			a = adjacent(&ms[i].entry.mz, &ms[j].entry.mz);
-
-			/* check if segments are adjacent virtually and/or physically but
-			 * not ioremap (since that would indicate that they are from
-			 * different PCI devices and thus don't need to be concatenated.
+			/* we're only interested in fully adjacent segments; partially
+			 * adjacent segments can coexist.
 			 */
-			if ((a & (VIRT|PHYS)) > 0 && (a & IOREMAP) == 0)
+			if (adjacent(&ms[i].entry.mz, &ms[j].entry.mz) == FULL)
 				return 1;
 		}
 	return 0;
-- 
2.5.0