RDMA/ocrdma: Don't sleep in atomic notifier handler

Events sent to ocrdma_inet6addr_event() are sent from an atomic context,
therefore we can't try to lock a mutex within the notifier callback.

We could just switch the mutex to a spinlock since all it does it
protect a list, but I've gone ahead and switched the list to use RCU
instead.  I couldn't fully test it since I don't have IB hardware, so
if it doesn't fully work for some reason let me know and I'll switch
it back to using a spinlock.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>

[ Fixed locking in ocrdma_add().  - Roland ]

Signed-off-by: Roland Dreier <roland@purestorage.com>

2 files changed, 23 insertions, 16 deletions

diff --git a/drivers/infiniband/hw/ocrdma/ocrdma.h b/drivers/infiniband/hw/ocrdma/ocrdma.h
index d7a44b812dfc..85a69c958559 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma.h
+++ b/drivers/infiniband/hw/ocrdma/ocrdma.h
@@ -168,6 +168,7 @@ struct ocrdma_dev {
         struct be_dev_info nic_info;
 
         struct list_head entry;
+        struct rcu_head rcu;
         int id;
 };
 
diff --git a/drivers/infiniband/hw/ocrdma/ocrdma_main.c b/drivers/infiniband/hw/ocrdma/ocrdma_main.c
index cee201ed14ae..0bc1efb02ff5 100644
--- a/drivers/infiniband/hw/ocrdma/ocrdma_main.c
+++ b/drivers/infiniband/hw/ocrdma/ocrdma_main.c
@@ -47,7 +47,7 @@ MODULE_AUTHOR("Emulex Corporation");
 MODULE_LICENSE("GPL");
 
 static LIST_HEAD(ocrdma_dev_list);
-static DEFINE_MUTEX(ocrdma_devlist_lock);
+static DEFINE_SPINLOCK(ocrdma_devlist_lock);
 static DEFINE_IDR(ocrdma_dev_id);
 
 static union ib_gid ocrdma_zero_sgid;
@@ -221,14 +221,14 @@ static int ocrdma_inet6addr_event(struct notifier_block *notifier,
                 is_vlan = true;
                 vid = vlan_dev_vlan_id(event_netdev);
         }
-        mutex_lock(&ocrdma_devlist_lock);
-        list_for_each_entry(dev, &ocrdma_dev_list, entry) {
+        rcu_read_lock();
+        list_for_each_entry_rcu(dev, &ocrdma_dev_list, entry) {
                 if (dev->nic_info.netdev == netdev) {
                         found = true;
                         break;
                 }
         }
-        mutex_unlock(&ocrdma_devlist_lock);
+        rcu_read_unlock();
 
         if (!found)
                 return NOTIFY_DONE;
@@ -431,9 +431,9 @@ static struct ocrdma_dev *ocrdma_add(struct be_dev_info *dev_info)
         if (status)
                 goto alloc_err;
 
-        mutex_lock(&ocrdma_devlist_lock);
-        list_add_tail(&dev->entry, &ocrdma_dev_list);
-        mutex_unlock(&ocrdma_devlist_lock);
+        spin_lock(&ocrdma_devlist_lock);
+        list_add_tail_rcu(&dev->entry, &ocrdma_dev_list);
+        spin_unlock(&ocrdma_devlist_lock);
         return dev;
 
 alloc_err:
@@ -448,16 +448,9 @@ idr_err:
         return NULL;
 }
 
-static void ocrdma_remove(struct ocrdma_dev *dev)
+static void ocrdma_remove_free(struct rcu_head *rcu)
 {
-        /* first unregister with stack to stop all the active traffic
-         * of the registered clients.
-         */
-        ib_unregister_device(&dev->ibdev);
-
-        mutex_lock(&ocrdma_devlist_lock);
-        list_del(&dev->entry);
-        mutex_unlock(&ocrdma_devlist_lock);
+        struct ocrdma_dev *dev = container_of(rcu, struct ocrdma_dev, rcu);
 
         ocrdma_free_resources(dev);
         ocrdma_cleanup_hw(dev);
@@ -467,6 +460,19 @@ static void ocrdma_remove(struct ocrdma_dev *dev)
         ib_dealloc_device(&dev->ibdev);
 }
 
+static void ocrdma_remove(struct ocrdma_dev *dev)
+{
+        /* first unregister with stack to stop all the active traffic
+         * of the registered clients.
+         */
+        ib_unregister_device(&dev->ibdev);
+
+        spin_lock(&ocrdma_devlist_lock);
+        list_del_rcu(&dev->entry);
+        spin_unlock(&ocrdma_devlist_lock);
+        call_rcu(&dev->rcu, ocrdma_remove_free);
+}
+
 static int ocrdma_open(struct ocrdma_dev *dev)
 {
         struct ib_event port_event;