On Sat, Feb 6, 2016 at 3:50 PM, Alex Estrin <alex.estrin@xxxxxxxxx> wrote: > A narrow window for race condition still exist between > multicast join thread and *dev_flush workers. > A kernel crash caused by prolong erratic link state changes > was observed (most likely a faulty cabling): > > [167275.656270] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000020 > [167275.665973] IP: [<ffffffffa05f8f2e>] ipoib_mcast_join+0xae/0x1d0 [ib_ipoib] > [167275.674443] PGD 0 > [167275.677373] Oops: 0000 [#1] SMP > ... > [167275.977530] Call Trace: > [167275.982225] [<ffffffffa05f92f0>] ? ipoib_mcast_free+0x200/0x200 [ib_ipoib] > [167275.992024] [<ffffffffa05fa1b7>] ipoib_mcast_join_task+0x2a7/0x490 > [ib_ipoib] > [167276.002149] [<ffffffff8109d5fb>] process_one_work+0x17b/0x470 > [167276.010754] [<ffffffff8109e3cb>] worker_thread+0x11b/0x400 > [167276.019088] [<ffffffff8109e2b0>] ? rescuer_thread+0x400/0x400 > [167276.027737] [<ffffffff810a5aef>] kthread+0xcf/0xe0 > Here was a hit spot: > ipoib_mcast_join() { > .............. > rec.qkey = priv->broadcast->mcmember.qkey; > ^^^^^^^ > ..... > } > Proposed patch should prevent multicast join task to continue > if link state change is detected. > > Signed-off-by: Alex Estrin <alex.estrin@xxxxxxxxx> > --- > > Changes from v1: > No need to lock again if error detected. > --- > drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 14 ++++++++++++-- > 1 files changed, 12 insertions(+), 2 deletions(-) > > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c > index 050dfa1..3ce2f0a 100644 > --- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c > +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c > @@ -456,7 +456,7 @@ out_locked: > return status; > } > > -static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) > +static int ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) > { > struct ipoib_dev_priv *priv = netdev_priv(dev); > struct ib_sa_multicast *multicast; > @@ -466,6 +466,9 @@ static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) > ib_sa_comp_mask comp_mask; > int ret = 0; > > + if (!priv->broadcast) > + return -EINVAL; > + Can you please elaborate what will avoid the other task that invalidate the priv->broadcast (ipoib_mcast_dev_flush) to do it right after that check? > ipoib_dbg_mcast(priv, "joining MGID %pI6\n", mcast->mcmember.mgid.raw); > > rec.mgid = mcast->mcmember.mgid; > @@ -539,6 +542,7 @@ static void ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast) > spin_unlock_irq(&priv->lock); > complete(&mcast->done); > } > + return 0; > } > > void ipoib_mcast_join_task(struct work_struct *work) > @@ -611,6 +615,11 @@ void ipoib_mcast_join_task(struct work_struct *work) > * and attached > */ > list_for_each_entry(mcast, &priv->multicast_list, list) { > + if (!test_bit(IPOIB_FLAG_OPER_UP, &priv->flags)) { > + mcast = NULL; > + delay_until = 0; > + goto out; > + } > if (IS_ERR_OR_NULL(mcast->mc) && > !test_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags) && > (!test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags) || > @@ -621,7 +630,8 @@ void ipoib_mcast_join_task(struct work_struct *work) > init_completion(&mcast->done); > set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags); > spin_unlock_irq(&priv->lock); > - ipoib_mcast_join(dev, mcast); > + if (ipoib_mcast_join(dev, mcast) != 0) > + return; > spin_lock_irq(&priv->lock); > } else if (!delay_until || > time_before(mcast->delay_until, delay_until)) > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html