IB/ipoib: Sync between remove_one to sysfs calls that use rtnl_lock

In order to avoid deadlock between sysfs functions (like create/delete
child) and remove_one (both of them are using the sysfs lock and
rtnl_lock) the driver will use a state mutex for sync.

That will fix traces as the following:
schedule+0x3e/0x90
kernfs_drain+0x75/0xf0
? wait_woken+0x90/0x90
__kernfs_remove+0x12e/0x1c0
kernfs_remove+0x25/0x40
sysfs_remove_dir+0x57/0x90
kobject_del+0x22/0x60
device_del+0x195/0x230
 pm_runtime_set_memalloc_noio+0xac/0xf0
netdev_unregister_kobject+0x71/0x80
rollback_registered_many+0x205/0x2f0
rollback_registered+0x31/0x40
unregister_netdevice_queue+0x58/0xb0
unregister_netdev+0x20/0x30
ipoib_remove_one+0xb7/0x240 [ib_ipoib]
ib_unregister_device+0xbc/0x1b0 [ib_core]
ib_unregister_mad_agent+0x29/0x30 [ib_core]
mlx4_ib_remove+0x67/0x280 [mlx4_ib]
INFO: task echo:24082 blocked for more than 120 seconds.
Tainted: G           OE   4.1.12-37.5.1.el6uek.x86_64 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
Call Trace:
schedule+0x3e/0x90
schedule_preempt_disabled+0xe/0x10
__mutex_lock_slowpath+0x95/0x110
? _rcu_barrier+0x177/0x220
mutex_lock+0x23/0x40
rtnl_lock+0x15/0x20
netdev_run_todo+0x81/0x1f0
rtnl_unlock+0xe/0x10
ipoib_vlan_delete+0x12f/0x1c0 [ib_ipoib]
delete_child+0x69/0x80 [ib_ipoib]
dev_attr_store+0x20/0x30
sysfs_kf_write+0x41/0x50

Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Reviewed-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -337,6 +337,7 @@ struct ipoib_dev_priv {
 
 	struct rw_semaphore vlan_rwsem;
 	struct mutex mcast_mutex;
+	struct mutex sysfs_mutex;
 
 	struct rb_root  path_tree;
 	struct list_head path_list;

drivers/infiniband/ulp/ipoib/ipoib_cm.c

@@ -1506,9 +1506,14 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
 	if (test_bit(IPOIB_FLAG_GOING_DOWN, &priv->flags))
 		return -EPERM;
 
-	if (!rtnl_trylock())
+	if (!mutex_trylock(&priv->sysfs_mutex))
 		return restart_syscall();
 
+	if (!rtnl_trylock()) {
+		mutex_unlock(&priv->sysfs_mutex);
+		return restart_syscall();
+	}
+
 	ret = ipoib_set_mode(dev, buf);
 
 	/* The assumption is that the function ipoib_set_mode returned
@@ -1517,6 +1522,7 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr,
 	 */
 	if (ret != -EBUSY)
 		rtnl_unlock();
+	mutex_unlock(&priv->sysfs_mutex);
 
 	return (!ret || ret == -EBUSY) ? count : ret;
 }

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -1878,6 +1878,7 @@ static void ipoib_build_priv(struct net_device *dev)
 	spin_lock_init(&priv->lock);
 	init_rwsem(&priv->vlan_rwsem);
 	mutex_init(&priv->mcast_mutex);
+	mutex_init(&priv->sysfs_mutex);
 
 	INIT_LIST_HEAD(&priv->path_list);
 	INIT_LIST_HEAD(&priv->child_intfs);
@@ -2329,7 +2330,11 @@ static void ipoib_remove_one(struct ib_device *device, void *client_data)
 		cancel_delayed_work(&priv->neigh_reap_task);
 		flush_workqueue(priv->wq);
 
+		/* Wrap rtnl_lock/unlock with mutex to protect sysfs calls */
+		mutex_lock(&priv->sysfs_mutex);
 		unregister_netdev(priv->dev);
+		mutex_unlock(&priv->sysfs_mutex);
+
 		rn->free_rdma_netdev(priv->dev);
 
 		list_for_each_entry_safe(cpriv, tcpriv, &priv->child_intfs, list)

drivers/infiniband/ulp/ipoib/ipoib_vlan.c

@@ -133,12 +133,20 @@ int ipoib_vlan_add(struct net_device *pdev, unsigned short pkey)
 	snprintf(intf_name, sizeof intf_name, "%s.%04x",
 		 ppriv->dev->name, pkey);
 
-	if (!rtnl_trylock())
+	if (!mutex_trylock(&ppriv->sysfs_mutex))
 		return restart_syscall();
 
+	if (!rtnl_trylock()) {
+		mutex_unlock(&ppriv->sysfs_mutex);
+		return restart_syscall();
+	}
+
 	priv = ipoib_intf_alloc(ppriv->ca, ppriv->port, intf_name);
-	if (!priv)
+	if (!priv) {
+		rtnl_unlock();
+		mutex_unlock(&ppriv->sysfs_mutex);
 		return -ENOMEM;
+	}
 
 	down_write(&ppriv->vlan_rwsem);
 
@@ -164,8 +172,8 @@ int ipoib_vlan_add(struct net_device *pdev, unsigned short pkey)
 
 out:
 	up_write(&ppriv->vlan_rwsem);
-
 	rtnl_unlock();
+	mutex_unlock(&ppriv->sysfs_mutex);
 
 	if (result) {
 		free_netdev(priv->dev);
@@ -188,8 +196,13 @@ int ipoib_vlan_delete(struct net_device *pdev, unsigned short pkey)
 	if (test_bit(IPOIB_FLAG_GOING_DOWN, &ppriv->flags))
 		return -EPERM;
 
-	if (!rtnl_trylock())
+	if (!mutex_trylock(&ppriv->sysfs_mutex))
+		return restart_syscall();
+
+	if (!rtnl_trylock()) {
+		mutex_unlock(&ppriv->sysfs_mutex);
 		return restart_syscall();
+	}
 
 	down_write(&ppriv->vlan_rwsem);
 	list_for_each_entry_safe(priv, tpriv, &ppriv->child_intfs, list) {
@@ -208,6 +221,7 @@ int ipoib_vlan_delete(struct net_device *pdev, unsigned short pkey)
 	}
 
 	rtnl_unlock();
+	mutex_unlock(&ppriv->sysfs_mutex);
 
 	if (dev) {
 		free_netdev(dev);