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authorJason Gunthorpe <jgg@mellanox.com>2019-10-01 18:38:19 +0300
committerJason Gunthorpe <jgg@mellanox.com>2019-10-04 21:54:22 +0300
commitaa116b810ac9077a263ed8679fb4d595f180e0eb (patch)
tree0e00e8d84c48e8ce53d2035207be218238e1ebf1 /drivers/infiniband
parent9dc775e7f5508f848661bbfb2e15683affb85f24 (diff)
downloadlinux-aa116b810ac9077a263ed8679fb4d595f180e0eb.tar.xz
RDMA/mlx5: Order num_pending_prefetch properly with synchronize_srcu
During destroy setting live = 0 and then synchronize_srcu() prevents num_pending_prefetch from incrementing, and also, ensures that all work holding that count is queued on the WQ. Testing before causes races of the form: CPU0 CPU1 dereg_mr() mlx5_ib_advise_mr_prefetch() srcu_read_lock() num_pending_prefetch_inc() if (!live) live = 0 atomic_read() == 0 // skip flush_workqueue() atomic_inc() queue_work(); srcu_read_unlock() WARN_ON(atomic_read()) // Fails Swap the order so that the synchronize_srcu() prevents this. Fixes: a6bc3875f176 ("IB/mlx5: Protect against prefetch of invalid MR") Link: https://lore.kernel.org/r/20191001153821.23621-5-jgg@ziepe.ca Reviewed-by: Artemy Kovalyov <artemyko@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'drivers/infiniband')
-rw-r--r--drivers/infiniband/hw/mlx5/mr.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index e7f840f306e4..0ee8fa01177f 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1609,13 +1609,14 @@ static void dereg_mr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr)
*/
mr->live = 0;
+ /* Wait for all running page-fault handlers to finish. */
+ synchronize_srcu(&dev->mr_srcu);
+
/* dequeue pending prefetch requests for the mr */
if (atomic_read(&mr->num_pending_prefetch))
flush_workqueue(system_unbound_wq);
WARN_ON(atomic_read(&mr->num_pending_prefetch));
- /* Wait for all running page-fault handlers to finish. */
- synchronize_srcu(&dev->mr_srcu);
/* Destroy all page mappings */
if (!umem_odp->is_implicit_odp)
mlx5_ib_invalidate_range(umem_odp,