[PATCH net-next 3/5] net/mlx4_core: Use RCU to perform radix tree lookup for SRQ

[Tariq Toukan]

From: Leon Romanovsky <leo...@mellanox.com>

Radix tree lookup can be performed without locking.

Fixes: 225c7b1feef1 ("IB/mlx4: Add a driver Mellanox ConnectX InfiniBand 
adapters")
Suggested-by: Sagi Grimberg <s...@grimberg.me>
Signed-off-by: Leon Romanovsky <leo...@mellanox.com>
Signed-off-by: Tariq Toukan <tar...@mellanox.com>
---
 drivers/net/ethernet/mellanox/mlx4/srq.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/srq.c 
b/drivers/net/ethernet/mellanox/mlx4/srq.c
index 67146624eb58..f44d089e2ca6 100644
--- a/drivers/net/ethernet/mellanox/mlx4/srq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/srq.c
@@ -45,15 +45,12 @@ void mlx4_srq_event(struct mlx4_dev *dev, u32 srqn, int 
event_type)
        struct mlx4_srq_table *srq_table = &mlx4_priv(dev)->srq_table;
        struct mlx4_srq *srq;
 
-       spin_lock(&srq_table->lock);
-
+       rcu_read_lock();
        srq = radix_tree_lookup(&srq_table->tree, srqn & (dev->caps.num_srqs - 
1));
+       rcu_read_unlock();
        if (srq)
                atomic_inc(&srq->refcount);
-
-       spin_unlock(&srq_table->lock);
-
-       if (!srq) {
+       else {
                mlx4_warn(dev, "Async event for bogus SRQ %08x\n", srqn);
                return;
        }
@@ -301,12 +298,11 @@ struct mlx4_srq *mlx4_srq_lookup(struct mlx4_dev *dev, 
u32 srqn)
 {
        struct mlx4_srq_table *srq_table = &mlx4_priv(dev)->srq_table;
        struct mlx4_srq *srq;
-       unsigned long flags;
 
-       spin_lock_irqsave(&srq_table->lock, flags);
+       rcu_read_lock();
        srq = radix_tree_lookup(&srq_table->tree,
                                srqn & (dev->caps.num_srqs - 1));
-       spin_unlock_irqrestore(&srq_table->lock, flags);
+       rcu_read_unlock();
 
        return srq;
 }
-- 
1.8.3.1