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authorArtemy Kovalyov <artemyko@mellanox.com>2020-02-27 13:39:18 +0200
committerJason Gunthorpe <jgg@mellanox.com>2020-03-04 13:25:00 -0400
commitde5ed007a03d71daaa505f5daa4d3666530c7090 (patch)
tree919b5bb1d3cdf638fec20aa2da669949e19c1601 /drivers/infiniband
parentIB/hfi1, qib: Ensure RCU is locked when accessing list (diff)
downloadlinux-dev-de5ed007a03d71daaa505f5daa4d3666530c7090.tar.xz
linux-dev-de5ed007a03d71daaa505f5daa4d3666530c7090.zip
IB/mlx5: Fix implicit ODP race
Following race may occur because of the call_srcu and the placement of the synchronize_srcu vs the xa_erase. CPU0 CPU1 mlx5_ib_free_implicit_mr: destroy_unused_implicit_child_mr: xa_erase(odp_mkeys) synchronize_srcu() xa_lock(implicit_children) if (still in xarray) atomic_inc() call_srcu() xa_unlock(implicit_children) xa_erase(implicit_children): xa_lock(implicit_children) __xa_erase() xa_unlock(implicit_children) flush_workqueue() [..] free_implicit_child_mr_rcu: (via call_srcu) queue_work() WARN_ON(atomic_read()) [..] free_implicit_child_mr_work: (via wq) free_implicit_child_mr() mlx5_mr_cache_invalidate() mlx5_ib_update_xlt() <-- UMR QP fail atomic_dec() The wait_event() solves the race because it blocks until free_implicit_child_mr_work() completes. Fixes: 5256edcb98a1 ("RDMA/mlx5: Rework implicit ODP destroy") Link: https://lore.kernel.org/r/20200227113918.94432-1-leon@kernel.org Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com> Reviewed-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'drivers/infiniband')
-rw-r--r--drivers/infiniband/hw/mlx5/mlx5_ib.h1
-rw-r--r--drivers/infiniband/hw/mlx5/odp.c17
2 files changed, 8 insertions, 10 deletions
diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index d9bffcc93587..bb78142bca5e 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -636,6 +636,7 @@ struct mlx5_ib_mr {
/* For ODP and implicit */
atomic_t num_deferred_work;
+ wait_queue_head_t q_deferred_work;
struct xarray implicit_children;
union {
struct rcu_head rcu;
diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 4216814ba871..bf50cd91f472 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -235,7 +235,8 @@ static void free_implicit_child_mr(struct mlx5_ib_mr *mr, bool need_imr_xlt)
mr->parent = NULL;
mlx5_mr_cache_free(mr->dev, mr);
ib_umem_odp_release(odp);
- atomic_dec(&imr->num_deferred_work);
+ if (atomic_dec_and_test(&imr->num_deferred_work))
+ wake_up(&imr->q_deferred_work);
}
static void free_implicit_child_mr_work(struct work_struct *work)
@@ -554,6 +555,7 @@ struct mlx5_ib_mr *mlx5_ib_alloc_implicit_mr(struct mlx5_ib_pd *pd,
imr->umem = &umem_odp->umem;
imr->is_odp_implicit = true;
atomic_set(&imr->num_deferred_work, 0);
+ init_waitqueue_head(&imr->q_deferred_work);
xa_init(&imr->implicit_children);
err = mlx5_ib_update_xlt(imr, 0,
@@ -611,10 +613,7 @@ void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr)
* under xa_lock while the child is in the xarray. Thus at this point
* it is only decreasing, and all work holding it is now on the wq.
*/
- if (atomic_read(&imr->num_deferred_work)) {
- flush_workqueue(system_unbound_wq);
- WARN_ON(atomic_read(&imr->num_deferred_work));
- }
+ wait_event(imr->q_deferred_work, !atomic_read(&imr->num_deferred_work));
/*
* Fence the imr before we destroy the children. This allows us to
@@ -645,10 +644,7 @@ void mlx5_ib_fence_odp_mr(struct mlx5_ib_mr *mr)
/* Wait for all running page-fault handlers to finish. */
synchronize_srcu(&mr->dev->odp_srcu);
- if (atomic_read(&mr->num_deferred_work)) {
- flush_workqueue(system_unbound_wq);
- WARN_ON(atomic_read(&mr->num_deferred_work));
- }
+ wait_event(mr->q_deferred_work, !atomic_read(&mr->num_deferred_work));
dma_fence_odp_mr(mr);
}
@@ -1720,7 +1716,8 @@ static void destroy_prefetch_work(struct prefetch_mr_work *work)
u32 i;
for (i = 0; i < work->num_sge; ++i)
- atomic_dec(&work->frags[i].mr->num_deferred_work);
+ if (atomic_dec_and_test(&work->frags[i].mr->num_deferred_work))
+ wake_up(&work->frags[i].mr->q_deferred_work);
kvfree(work);
}