From: Alex Vesker valex@mellanox.com
commit 1f80bd6a6cc8358b81194e1f5fc16449947396ec upstream.
The locking order of vlan_rwsem (LOCK A) and then rtnl (LOCK B), contradicts other flows such as ipoib_open possibly causing a deadlock. To prevent this deadlock heavy flush is called with RTNL locked and only then tries to acquire vlan_rwsem. This deadlock is possible only when there are child interfaces.
[ 140.941758] ====================================================== [ 140.946276] WARNING: possible circular locking dependency detected [ 140.950950] 4.15.0-rc1+ #9 Tainted: G O [ 140.954797] ------------------------------------------------------ [ 140.959424] kworker/u32:1/146 is trying to acquire lock: [ 140.963450] (rtnl_mutex){+.+.}, at: [<ffffffffc083516a>] __ipoib_ib_dev_flush+0x2da/0x4e0 [ib_ipoib] [ 140.970006] but task is already holding lock: [ 140.975141] (&priv->vlan_rwsem){++++}, at: [<ffffffffc0834ee1>] __ipoib_ib_dev_flush+0x51/0x4e0 [ib_ipoib] [ 140.982105] which lock already depends on the new lock. [ 140.990023] the existing dependency chain (in reverse order) is: [ 140.998650] -> #1 (&priv->vlan_rwsem){++++}: [ 141.005276] down_read+0x4d/0xb0 [ 141.009560] ipoib_open+0xad/0x120 [ib_ipoib] [ 141.014400] __dev_open+0xcb/0x140 [ 141.017919] __dev_change_flags+0x1a4/0x1e0 [ 141.022133] dev_change_flags+0x23/0x60 [ 141.025695] devinet_ioctl+0x704/0x7d0 [ 141.029156] sock_do_ioctl+0x20/0x50 [ 141.032526] sock_ioctl+0x221/0x300 [ 141.036079] do_vfs_ioctl+0xa6/0x6d0 [ 141.039656] SyS_ioctl+0x74/0x80 [ 141.042811] entry_SYSCALL_64_fastpath+0x1f/0x96 [ 141.046891] -> #0 (rtnl_mutex){+.+.}: [ 141.051701] lock_acquire+0xd4/0x220 [ 141.055212] __mutex_lock+0x88/0x970 [ 141.058631] __ipoib_ib_dev_flush+0x2da/0x4e0 [ib_ipoib] [ 141.063160] __ipoib_ib_dev_flush+0x71/0x4e0 [ib_ipoib] [ 141.067648] process_one_work+0x1f5/0x610 [ 141.071429] worker_thread+0x4a/0x3f0 [ 141.074890] kthread+0x141/0x180 [ 141.078085] ret_from_fork+0x24/0x30 [ 141.081559]
other info that might help us debug this: [ 141.088967] Possible unsafe locking scenario: [ 141.094280] CPU0 CPU1 [ 141.097953] ---- ---- [ 141.101640] lock(&priv->vlan_rwsem); [ 141.104771] lock(rtnl_mutex); [ 141.109207] lock(&priv->vlan_rwsem); [ 141.114032] lock(rtnl_mutex); [ 141.116800] *** DEADLOCK ***
Fixes: b4b678b06f6e ("IB/ipoib: Grab rtnl lock on heavy flush when calling ndo_open/stop") Signed-off-by: Alex Vesker valex@mellanox.com Signed-off-by: Leon Romanovsky leon@kernel.org Signed-off-by: Jason Gunthorpe jgg@mellanox.com Cc: Guenter Roeck linux@roeck-us.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/infiniband/ulp/ipoib/ipoib_ib.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c @@ -1057,13 +1057,10 @@ static void __ipoib_ib_dev_flush(struct ipoib_ib_dev_down(dev);
if (level == IPOIB_FLUSH_HEAVY) { - rtnl_lock(); if (test_bit(IPOIB_FLAG_INITIALIZED, &priv->flags)) ipoib_ib_dev_stop(dev);
- result = ipoib_ib_dev_open(dev); - rtnl_unlock(); - if (result) + if (ipoib_ib_dev_open(dev)) return;
if (netif_queue_stopped(dev)) @@ -1102,7 +1099,9 @@ void ipoib_ib_dev_flush_heavy(struct wor struct ipoib_dev_priv *priv = container_of(work, struct ipoib_dev_priv, flush_heavy);
+ rtnl_lock(); __ipoib_ib_dev_flush(priv, IPOIB_FLUSH_HEAVY, 0); + rtnl_unlock(); }
void ipoib_ib_dev_cleanup(struct net_device *dev)