From 3e31a490e01a6e67cbe9f6e1df2f3ff0fbf48972 Mon Sep 17 00:00:00 2001 From: Feras Daoud Date: Sun, 19 Mar 2017 11:18:55 +0200 Subject: [PATCH] IB/ipoib: Fix deadlock between ipoib_stop and mcast join flow Before calling ipoib_stop, rtnl_lock should be taken, then the flow clears the IPOIB_FLAG_ADMIN_UP and IPOIB_FLAG_OPER_UP flags, and waits for mcast completion if IPOIB_MCAST_FLAG_BUSY is set. On the other hand, the flow of multicast join task initializes a mcast completion, sets the IPOIB_MCAST_FLAG_BUSY and calls ipoib_mcast_join. If IPOIB_FLAG_OPER_UP flag is not set, this call returns EINVAL without setting the mcast completion and leads to a deadlock. ipoib_stop | | | clear_bit(IPOIB_FLAG_ADMIN_UP) | | | Context Switch | | ipoib_mcast_join_task | | | spin_lock_irq(lock) | | | init_completion(mcast) | | | set_bit(IPOIB_MCAST_FLAG_BUSY) | | | Context Switch | | clear_bit(IPOIB_FLAG_OPER_UP) | | | spin_lock_irqsave(lock) | | | Context Switch | | ipoib_mcast_join | return (-EINVAL) | | | spin_unlock_irq(lock) | | | Context Switch | | ipoib_mcast_dev_flush | wait_for_completion(mcast) | ipoib_stop will wait for mcast completion for ever, and will not release the rtnl_lock. As a result panic occurs with the following trace: [13441.639268] Call Trace: [13441.640150] [] schedule+0x29/0x70 [13441.641038] [] schedule_timeout+0x239/0x2d0 [13441.641914] [] ? complete+0x47/0x50 [13441.642765] [] ? flush_workqueue_prep_pwqs+0x16d/0x200 [13441.643580] [] wait_for_completion+0x116/0x170 [13441.644434] [] ? wake_up_state+0x20/0x20 [13441.645293] [] ipoib_mcast_dev_flush+0x150/0x190 [ib_ipoib] [13441.646159] [] ipoib_ib_dev_down+0x37/0x60 [ib_ipoib] [13441.647013] [] ipoib_stop+0x75/0x150 [ib_ipoib] Fixes: 08bc327629cb ("IB/ipoib: fix for rare multicast join race condition") Signed-off-by: Feras Daoud Signed-off-by: Leon Romanovsky Signed-off-by: Doug Ledford --- drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c index 8da1955e0003..5433de83cdab 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c @@ -491,6 +491,9 @@ static int ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) !test_bit(IPOIB_FLAG_OPER_UP, &priv->flags)) return -EINVAL; + init_completion(&mcast->done); + set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags); + ipoib_dbg_mcast(priv, "joining MGID %pI6\n", mcast->mcmember.mgid.raw); rec.mgid = mcast->mcmember.mgid; @@ -649,8 +652,6 @@ void ipoib_mcast_join_task(struct work_struct *work) if (mcast->backoff == 1 || time_after_eq(jiffies, mcast->delay_until)) { /* Found the next unjoined group */ - init_completion(&mcast->done); - set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags); if (ipoib_mcast_join(dev, mcast)) { spin_unlock_irq(&priv->lock); return; @@ -670,11 +671,9 @@ out: queue_delayed_work(priv->wq, &priv->mcast_task, delay_until - jiffies); } - if (mcast) { - init_completion(&mcast->done); - set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags); + if (mcast) ipoib_mcast_join(dev, mcast); - } + spin_unlock_irq(&priv->lock); } -- 2.30.2