From: Jason Gunthorpe <jgg@mellanox.com>
Date: Sun, 29 Jul 2018 11:34:57 +0300
Subject: IB/ipoib: Get rid of the sysfs_mutex
Patch-mainline: v4.19-rc1
Git-commit: ee190ab734ba4d3c7887bd193ce8124385738e44
References: bsc#1103992 FATE#326009
This mutex was introduced to deal with the deadlock formed by calling
unregister_netdev from within the sysfs callback of a netdev.
Now that we have priv_destructor and needs_free_netdev we can switch
to the more targeted solution of running the unregister from a
work queue. This avoids the deadlock and gets rid of the mutex.
The next patch in the series needs this mutex eliminated to create
atomicity of unregisteration.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
drivers/infiniband/ulp/ipoib/ipoib.h | 1
drivers/infiniband/ulp/ipoib/ipoib_cm.c | 7 --
drivers/infiniband/ulp/ipoib/ipoib_main.c | 7 --
drivers/infiniband/ulp/ipoib/ipoib_vlan.c | 98 +++++++++++++++++++-----------
4 files changed, 65 insertions(+), 48 deletions(-)
--- a/drivers/infiniband/ulp/ipoib/ipoib.h
+++ b/drivers/infiniband/ulp/ipoib/ipoib.h
@@ -332,7 +332,6 @@ 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;
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -1517,19 +1517,13 @@ static ssize_t set_mode(struct device *d
{
struct net_device *dev = to_net_dev(d);
int ret;
- struct ipoib_dev_priv *priv = ipoib_priv(dev);
-
- if (!mutex_trylock(&priv->sysfs_mutex))
- return restart_syscall();
if (!rtnl_trylock()) {
- mutex_unlock(&priv->sysfs_mutex);
return restart_syscall();
}
if (dev->reg_state != NETREG_REGISTERED) {
rtnl_unlock();
- mutex_unlock(&priv->sysfs_mutex);
return -EPERM;
}
@@ -1541,7 +1535,6 @@ static ssize_t set_mode(struct device *d
*/
if (ret != -EBUSY)
rtnl_unlock();
- mutex_unlock(&priv->sysfs_mutex);
return (!ret || ret == -EBUSY) ? count : ret;
}
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -2077,7 +2077,6 @@ static void ipoib_build_priv(struct net_
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);
@@ -2474,10 +2473,7 @@ static void ipoib_remove_one(struct ib_d
list_for_each_entry_safe(priv, tmp, dev_list, list) {
ipoib_parent_unregister_pre(priv->dev);
- /* Wrap rtnl_lock/unlock with mutex to protect sysfs calls */
- mutex_lock(&priv->sysfs_mutex);
unregister_netdev(priv->dev);
- mutex_unlock(&priv->sysfs_mutex);
}
kfree(dev_list);
@@ -2525,8 +2521,7 @@ static int __init ipoib_init_module(void
* its private workqueue, and we only queue up flush events
* on our global flush workqueue. This avoids the deadlocks.
*/
- ipoib_workqueue = alloc_ordered_workqueue("ipoib_flush",
- WQ_MEM_RECLAIM);
+ ipoib_workqueue = alloc_ordered_workqueue("ipoib_flush", 0);
if (!ipoib_workqueue) {
ret = -ENOMEM;
goto err_fs;
--- a/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_vlan.c
@@ -125,23 +125,16 @@ int ipoib_vlan_add(struct net_device *pd
snprintf(intf_name, sizeof(intf_name), "%s.%04x",
ppriv->dev->name, pkey);
- if (!mutex_trylock(&ppriv->sysfs_mutex))
+ if (!rtnl_trylock())
return restart_syscall();
- if (!rtnl_trylock()) {
- mutex_unlock(&ppriv->sysfs_mutex);
- return restart_syscall();
- }
-
if (pdev->reg_state != NETREG_REGISTERED) {
rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
return -EPERM;
}
if (!down_write_trylock(&ppriv->vlan_rwsem)) {
rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
return restart_syscall();
}
@@ -178,58 +171,95 @@ int ipoib_vlan_add(struct net_device *pd
out:
up_write(&ppriv->vlan_rwsem);
rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
return result;
}
+struct ipoib_vlan_delete_work {
+ struct work_struct work;
+ struct net_device *dev;
+};
+
+/*
+ * sysfs callbacks of a netdevice cannot obtain the rtnl lock as
+ * unregister_netdev ultimately deletes the sysfs files while holding the rtnl
+ * lock. This deadlocks the system.
+ *
+ * A callback can use rtnl_trylock to avoid the deadlock but it cannot call
+ * unregister_netdev as that internally takes and releases the rtnl_lock. So
+ * instead we find the netdev to unregister and then do the actual unregister
+ * from the global work queue where we can obtain the rtnl_lock safely.
+ */
+static void ipoib_vlan_delete_task(struct work_struct *work)
+{
+ struct ipoib_vlan_delete_work *pwork =
+ container_of(work, struct ipoib_vlan_delete_work, work);
+ struct net_device *dev = pwork->dev;
+
+ rtnl_lock();
+
+ /* Unregistering tasks can race with another task or parent removal */
+ if (dev->reg_state == NETREG_REGISTERED) {
+ struct ipoib_dev_priv *priv = ipoib_priv(dev);
+ struct ipoib_dev_priv *ppriv = ipoib_priv(priv->parent);
+
+ down_write(&ppriv->vlan_rwsem);
+ list_del(&priv->list);
+ up_write(&ppriv->vlan_rwsem);
+
+ ipoib_dbg(ppriv, "delete child vlan %s\n", dev->name);
+ unregister_netdevice(dev);
+ }
+
+ rtnl_unlock();
+
+ kfree(pwork);
+}
+
int ipoib_vlan_delete(struct net_device *pdev, unsigned short pkey)
{
struct ipoib_dev_priv *ppriv, *priv, *tpriv;
- struct net_device *dev = NULL;
+ int rc;
if (!capable(CAP_NET_ADMIN))
return -EPERM;
- ppriv = ipoib_priv(pdev);
-
- if (!mutex_trylock(&ppriv->sysfs_mutex))
+ if (!rtnl_trylock())
return restart_syscall();
- if (!rtnl_trylock()) {
- mutex_unlock(&ppriv->sysfs_mutex);
- return restart_syscall();
- }
-
if (pdev->reg_state != NETREG_REGISTERED) {
rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
return -EPERM;
}
- if (!down_write_trylock(&ppriv->vlan_rwsem)) {
- rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
- return restart_syscall();
- }
+ ppriv = ipoib_priv(pdev);
+ rc = -ENODEV;
list_for_each_entry_safe(priv, tpriv, &ppriv->child_intfs, list) {
if (priv->pkey == pkey &&
priv->child_type == IPOIB_LEGACY_CHILD) {
- list_del(&priv->list);
- dev = priv->dev;
+ struct ipoib_vlan_delete_work *work;
+
+ work = kmalloc(sizeof(*work), GFP_KERNEL);
+ if (!work) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ down_write(&ppriv->vlan_rwsem);
+ list_del_init(&priv->list);
+ up_write(&ppriv->vlan_rwsem);
+ work->dev = priv->dev;
+ INIT_WORK(&work->work, ipoib_vlan_delete_task);
+ queue_work(ipoib_workqueue, &work->work);
+
+ rc = 0;
break;
}
}
- up_write(&ppriv->vlan_rwsem);
-
- if (dev) {
- ipoib_dbg(ppriv, "delete child vlan %s\n", dev->name);
- unregister_netdevice(dev);
- }
+out:
rtnl_unlock();
- mutex_unlock(&ppriv->sysfs_mutex);
- return (dev) ? 0 : -ENODEV;
+ return rc;
}