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authorErez Shitrit <erezsh@mellanox.com>2017-12-31 15:33:15 +0200
committerJason Gunthorpe <jgg@mellanox.com>2018-01-02 11:09:05 -0700
commit16ba3defb8bd01a9464ba4820a487f5b196b455b (patch)
tree9492fce56c1f5e95c6da8ecafa3739ec9fd9d598 /drivers/infiniband/ulp/ipoib/ipoib_multicast.c
parent5a371cf87e145b86efd32007e46146e78c1eff6d (diff)
downloadlinux-16ba3defb8bd01a9464ba4820a487f5b196b455b.tar.bz2
IB/ipoib: Fix race condition in neigh creation
When using enhanced mode for IPoIB, two threads may execute xmit in parallel to two different TX queues while the target is the same. In this case, both of them will add the same neighbor to the path's neigh link list and we might see the following message: list_add double add: new=ffff88024767a348, prev=ffff88024767a348... WARNING: lib/list_debug.c:31__list_add_valid+0x4e/0x70 ipoib_start_xmit+0x477/0x680 [ib_ipoib] dev_hard_start_xmit+0xb9/0x3e0 sch_direct_xmit+0xf9/0x250 __qdisc_run+0x176/0x5d0 __dev_queue_xmit+0x1f5/0xb10 __dev_queue_xmit+0x55/0xb10 Analysis: Two SKB are scheduled to be transmitted from two cores. In ipoib_start_xmit, both gets NULL when calling ipoib_neigh_get. Two calls to neigh_add_path are made. One thread takes the spin-lock and calls ipoib_neigh_alloc which creates the neigh structure, then (after the __path_find) the neigh is added to the path's neigh link list. When the second thread enters the critical section it also calls ipoib_neigh_alloc but in this case it gets the already allocated ipoib_neigh structure, which is already linked to the path's neigh link list and adds it again to the list. Which beside of triggering the list, it creates a loop in the linked list. This loop leads to endless loop inside path_rec_completion. Solution: Check list_empty(&neigh->list) before adding to the list. Add a similar fix in "ipoib_multicast.c::ipoib_mcast_send" Fixes: b63b70d87741 ('IPoIB: Use a private hash table for path lookup in xmit path') Signed-off-by: Erez Shitrit <erezsh@mellanox.com> Reviewed-by: Alex Vesker <valex@mellanox.com> Signed-off-by: Leon Romanovsky <leon@kernel.org> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'drivers/infiniband/ulp/ipoib/ipoib_multicast.c')
-rw-r--r--drivers/infiniband/ulp/ipoib/ipoib_multicast.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index 93e149efc1f5..9b3f47ae2016 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -816,7 +816,10 @@ void ipoib_mcast_send(struct net_device *dev, u8 *daddr, struct sk_buff *skb)
spin_lock_irqsave(&priv->lock, flags);
if (!neigh) {
neigh = ipoib_neigh_alloc(daddr, dev);
- if (neigh) {
+ /* Make sure that the neigh will be added only
+ * once to mcast list.
+ */
+ if (neigh && list_empty(&neigh->list)) {
kref_get(&mcast->ah->ref);
neigh->ah = mcast->ah;
list_add_tail(&neigh->list, &mcast->neigh_list);