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authorJack Morgenstein <jackm@dev.mellanox.co.il>2017-01-16 18:31:37 +0200
committerDavid S. Miller <davem@davemloft.net>2017-01-16 15:08:28 -0500
commit291c566a28910614ce42d0ffe82196eddd6346f4 (patch)
tree38802eb467700b98105547b95c2850c32785ce90 /drivers
parentb618ab4561d40664492cf9f9507f19a1c8272970 (diff)
net/mlx4_core: Fix racy CQ (Completion Queue) free
In function mlx4_cq_completion() and mlx4_cq_event(), the radix_tree_lookup requires a rcu_read_lock. This is mandatory: if another core frees the CQ, it could run the radix_tree_node_rcu_free() call_rcu() callback while its being used by the radix tree lookup function. Additionally, in function mlx4_cq_event(), since we are adding the rcu lock around the radix-tree lookup, we no longer need to take the spinlock. Also, the synchronize_irq() call for the async event eliminates the need for incrementing the cq reference count in mlx4_cq_event(). Other changes: 1. In function mlx4_cq_free(), replace spin_lock_irq with spin_lock: we no longer take this spinlock in the interrupt context. The spinlock here, therefore, simply protects against different threads simultaneously invoking mlx4_cq_free() for different cq's. 2. In function mlx4_cq_free(), we move the radix tree delete to before the synchronize_irq() calls. This guarantees that we will not access this cq during any subsequent interrupts, and therefore can safely free the CQ after the synchronize_irq calls. The rcu_read_lock in the interrupt handlers only needs to protect against corrupting the radix tree; the interrupt handlers may access the cq outside the rcu_read_lock due to the synchronize_irq calls which protect against premature freeing of the cq. 3. In function mlx4_cq_event(), we change the mlx_warn message to mlx4_dbg. 4. We leave the cq reference count mechanism in place, because it is still needed for the cq completion tasklet mechanism. Fixes: 6d90aa5cf17b ("net/mlx4_core: Make sure there are no pending async events when freeing CQ") Fixes: 225c7b1feef1 ("IB/mlx4: Add a driver Mellanox ConnectX InfiniBand adapters") Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il> Signed-off-by: Matan Barak <matanb@mellanox.com> Signed-off-by: Tariq Toukan <tariqt@mellanox.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/net/ethernet/mellanox/mlx4/cq.c38
1 files changed, 20 insertions, 18 deletions
diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index a849da92f857..6b8635378f1f 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
@@ -101,13 +101,19 @@ void mlx4_cq_completion(struct mlx4_dev *dev, u32 cqn)
{
struct mlx4_cq *cq;
+ rcu_read_lock();
cq = radix_tree_lookup(&mlx4_priv(dev)->cq_table.tree,
cqn & (dev->caps.num_cqs - 1));
+ rcu_read_unlock();
+
if (!cq) {
mlx4_dbg(dev, "Completion event for bogus CQ %08x\n", cqn);
return;
}
+ /* Acessing the CQ outside of rcu_read_lock is safe, because
+ * the CQ is freed only after interrupt handling is completed.
+ */
++cq->arm_sn;
cq->comp(cq);
@@ -118,23 +124,19 @@ void mlx4_cq_event(struct mlx4_dev *dev, u32 cqn, int event_type)
struct mlx4_cq_table *cq_table = &mlx4_priv(dev)->cq_table;
struct mlx4_cq *cq;
- spin_lock(&cq_table->lock);
-
+ rcu_read_lock();
cq = radix_tree_lookup(&cq_table->tree, cqn & (dev->caps.num_cqs - 1));
- if (cq)
- atomic_inc(&cq->refcount);
-
- spin_unlock(&cq_table->lock);
+ rcu_read_unlock();
if (!cq) {
- mlx4_warn(dev, "Async event for bogus CQ %08x\n", cqn);
+ mlx4_dbg(dev, "Async event for bogus CQ %08x\n", cqn);
return;
}
+ /* Acessing the CQ outside of rcu_read_lock is safe, because
+ * the CQ is freed only after interrupt handling is completed.
+ */
cq->event(cq, event_type);
-
- if (atomic_dec_and_test(&cq->refcount))
- complete(&cq->free);
}
static int mlx4_SW2HW_CQ(struct mlx4_dev *dev, struct mlx4_cmd_mailbox *mailbox,
@@ -301,9 +303,9 @@ int mlx4_cq_alloc(struct mlx4_dev *dev, int nent,
if (err)
return err;
- spin_lock_irq(&cq_table->lock);
+ spin_lock(&cq_table->lock);
err = radix_tree_insert(&cq_table->tree, cq->cqn, cq);
- spin_unlock_irq(&cq_table->lock);
+ spin_unlock(&cq_table->lock);
if (err)
goto err_icm;
@@ -349,9 +351,9 @@ int mlx4_cq_alloc(struct mlx4_dev *dev, int nent,
return 0;
err_radix:
- spin_lock_irq(&cq_table->lock);
+ spin_lock(&cq_table->lock);
radix_tree_delete(&cq_table->tree, cq->cqn);
- spin_unlock_irq(&cq_table->lock);
+ spin_unlock(&cq_table->lock);
err_icm:
mlx4_cq_free_icm(dev, cq->cqn);
@@ -370,15 +372,15 @@ void mlx4_cq_free(struct mlx4_dev *dev, struct mlx4_cq *cq)
if (err)
mlx4_warn(dev, "HW2SW_CQ failed (%d) for CQN %06x\n", err, cq->cqn);
+ spin_lock(&cq_table->lock);
+ radix_tree_delete(&cq_table->tree, cq->cqn);
+ spin_unlock(&cq_table->lock);
+
synchronize_irq(priv->eq_table.eq[MLX4_CQ_TO_EQ_VECTOR(cq->vector)].irq);
if (priv->eq_table.eq[MLX4_CQ_TO_EQ_VECTOR(cq->vector)].irq !=
priv->eq_table.eq[MLX4_EQ_ASYNC].irq)
synchronize_irq(priv->eq_table.eq[MLX4_EQ_ASYNC].irq);
- spin_lock_irq(&cq_table->lock);
- radix_tree_delete(&cq_table->tree, cq->cqn);
- spin_unlock_irq(&cq_table->lock);
-
if (atomic_dec_and_test(&cq->refcount))
complete(&cq->free);
wait_for_completion(&cq->free);