From: Shiraz Saleem shiraz.saleem@intel.com
commit 2df6d895907b2f5dfbc558cbff7801bba82cb3cc upstream.
QP destroy is synchronous and waits for its refcnt to be decremented in irdma_cm_node_free_cb (for iWARP) which fires after the RCU grace period elapses.
Applications running a large number of connections are exposed to high wait times on destroy QP for events like SIGABORT.
The long pole for this wait time is the firing of the call_rcu callback during a CM node destroy which can be slow. It holds the QP reference count and blocks the destroy QP from completing.
call_rcu only needs to make sure that list walkers have a reference to the cm_node object before freeing it and thus need to wait for grace period elapse. The rest of the connection teardown in irdma_cm_node_free_cb is moved out of the grace period wait in irdma_destroy_connection. Also, replace call_rcu with a simple kfree_rcu as it just needs to do a kfree on the cm_node
Fixes: 146b9756f14c ("RDMA/irdma: Add connection manager") Link: https://lore.kernel.org/r/20220425181703.1634-3-shiraz.saleem@intel.com Signed-off-by: Shiraz Saleem shiraz.saleem@intel.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/infiniband/hw/irdma/cm.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
--- a/drivers/infiniband/hw/irdma/cm.c +++ b/drivers/infiniband/hw/irdma/cm.c @@ -2305,10 +2305,8 @@ err: return NULL; }
-static void irdma_cm_node_free_cb(struct rcu_head *rcu_head) +static void irdma_destroy_connection(struct irdma_cm_node *cm_node) { - struct irdma_cm_node *cm_node = - container_of(rcu_head, struct irdma_cm_node, rcu_head); struct irdma_cm_core *cm_core = cm_node->cm_core; struct irdma_qp *iwqp; struct irdma_cm_info nfo; @@ -2356,7 +2354,6 @@ static void irdma_cm_node_free_cb(struct }
cm_core->cm_free_ah(cm_node); - kfree(cm_node); }
/** @@ -2384,8 +2381,9 @@ void irdma_rem_ref_cm_node(struct irdma_
spin_unlock_irqrestore(&cm_core->ht_lock, flags);
- /* wait for all list walkers to exit their grace period */ - call_rcu(&cm_node->rcu_head, irdma_cm_node_free_cb); + irdma_destroy_connection(cm_node); + + kfree_rcu(cm_node, rcu_head); }
/**