During my recent work on the rtnl lock deadlock in the IPoIB driver, I
saw that even once I fixed the apparent races for a single device, as
soon as that device had any children, new races popped up. It turns
out that this is because no matter how well we protect against races
on a single device, the fact that all devices use the same workqueue,
and flush_workqueue() flushes *everything* from that workqueue means
that we would also have to prevent all races between different devices
(for instance, ipoib_mcast_restart_task on interface ib0 can race with
ipoib_mcast_flush_dev on interface ib0.8002, resulting in a deadlock on
the rtnl_lock).
There are several possible solutions to this problem:
Make carrier_on_task and mcast_restart_task try to take the rtnl for
some set period of time and if they fail, then bail. This runs the
real risk of dropping work on the floor, which can end up being its
own separate kind of deadlock.
Set some global flag in the driver that says some device is in the
middle of going down, letting all tasks know to bail. Again, this can
drop work on the floor.
Or the method this patch attempts to use, which is when we bring an
interface up, create a workqueue specifically for that interface, so
that when we take it back down, we are flushing only those tasks
associated with our interface. In addition, keep the global
workqueue, but now limit it to only flush tasks. In this way, the
flush tasks can always flush the device specific work queues without
having deadlock issues.
Signed-off-by: Doug Ledford <dledford@redhat.com>
struct list_head multicast_list;
struct rb_root multicast_tree;
struct list_head multicast_list;
struct rb_root multicast_tree;
+ struct workqueue_struct *wq;
struct delayed_work mcast_task;
struct work_struct carrier_on_task;
struct work_struct flush_light;
struct delayed_work mcast_task;
struct work_struct carrier_on_task;
struct work_struct flush_light;
}
spin_lock_irq(&priv->lock);
}
spin_lock_irq(&priv->lock);
- queue_delayed_work(ipoib_workqueue,
+ queue_delayed_work(priv->wq,
&priv->cm.stale_task, IPOIB_CM_RX_DELAY);
/* Add this entry to passive ids list head, but do not re-add it
* if IB_EVENT_QP_LAST_WQE_REACHED has moved it to flush list. */
&priv->cm.stale_task, IPOIB_CM_RX_DELAY);
/* Add this entry to passive ids list head, but do not re-add it
* if IB_EVENT_QP_LAST_WQE_REACHED has moved it to flush list. */
spin_lock_irqsave(&priv->lock, flags);
list_splice_init(&priv->cm.rx_drain_list, &priv->cm.rx_reap_list);
ipoib_cm_start_rx_drain(priv);
spin_lock_irqsave(&priv->lock, flags);
list_splice_init(&priv->cm.rx_drain_list, &priv->cm.rx_reap_list);
ipoib_cm_start_rx_drain(priv);
- queue_work(ipoib_workqueue, &priv->cm.rx_reap_task);
+ queue_work(priv->wq, &priv->cm.rx_reap_task);
spin_unlock_irqrestore(&priv->lock, flags);
} else
ipoib_warn(priv, "cm recv completion event with wrid %d (> %d)\n",
spin_unlock_irqrestore(&priv->lock, flags);
} else
ipoib_warn(priv, "cm recv completion event with wrid %d (> %d)\n",
spin_lock_irqsave(&priv->lock, flags);
list_move(&p->list, &priv->cm.rx_reap_list);
spin_unlock_irqrestore(&priv->lock, flags);
spin_lock_irqsave(&priv->lock, flags);
list_move(&p->list, &priv->cm.rx_reap_list);
spin_unlock_irqrestore(&priv->lock, flags);
- queue_work(ipoib_workqueue, &priv->cm.rx_reap_task);
+ queue_work(priv->wq, &priv->cm.rx_reap_task);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
list_move(&tx->list, &priv->cm.reap_list);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
list_move(&tx->list, &priv->cm.reap_list);
- queue_work(ipoib_workqueue, &priv->cm.reap_task);
+ queue_work(priv->wq, &priv->cm.reap_task);
}
clear_bit(IPOIB_FLAG_OPER_UP, &tx->flags);
}
clear_bit(IPOIB_FLAG_OPER_UP, &tx->flags);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
list_move(&tx->list, &priv->cm.reap_list);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
list_move(&tx->list, &priv->cm.reap_list);
- queue_work(ipoib_workqueue, &priv->cm.reap_task);
+ queue_work(priv->wq, &priv->cm.reap_task);
}
spin_unlock_irqrestore(&priv->lock, flags);
}
spin_unlock_irqrestore(&priv->lock, flags);
tx->dev = dev;
list_add(&tx->list, &priv->cm.start_list);
set_bit(IPOIB_FLAG_INITIALIZED, &tx->flags);
tx->dev = dev;
list_add(&tx->list, &priv->cm.start_list);
set_bit(IPOIB_FLAG_INITIALIZED, &tx->flags);
- queue_work(ipoib_workqueue, &priv->cm.start_task);
+ queue_work(priv->wq, &priv->cm.start_task);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
spin_lock_irqsave(&priv->lock, flags);
list_move(&tx->list, &priv->cm.reap_list);
if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &tx->flags)) {
spin_lock_irqsave(&priv->lock, flags);
list_move(&tx->list, &priv->cm.reap_list);
- queue_work(ipoib_workqueue, &priv->cm.reap_task);
+ queue_work(priv->wq, &priv->cm.reap_task);
ipoib_dbg(priv, "Reap connection for gid %pI6\n",
tx->neigh->daddr + 4);
tx->neigh = NULL;
ipoib_dbg(priv, "Reap connection for gid %pI6\n",
tx->neigh->daddr + 4);
tx->neigh = NULL;
skb_queue_tail(&priv->cm.skb_queue, skb);
if (e)
skb_queue_tail(&priv->cm.skb_queue, skb);
if (e)
- queue_work(ipoib_workqueue, &priv->cm.skb_task);
+ queue_work(priv->wq, &priv->cm.skb_task);
}
static void ipoib_cm_rx_reap(struct work_struct *work)
}
static void ipoib_cm_rx_reap(struct work_struct *work)
}
if (!list_empty(&priv->cm.passive_ids))
}
if (!list_empty(&priv->cm.passive_ids))
- queue_delayed_work(ipoib_workqueue,
+ queue_delayed_work(priv->wq,
&priv->cm.stale_task, IPOIB_CM_RX_DELAY);
spin_unlock_irq(&priv->lock);
}
&priv->cm.stale_task, IPOIB_CM_RX_DELAY);
spin_unlock_irq(&priv->lock);
}
__ipoib_reap_ah(dev);
if (!test_bit(IPOIB_STOP_REAPER, &priv->flags))
__ipoib_reap_ah(dev);
if (!test_bit(IPOIB_STOP_REAPER, &priv->flags))
- queue_delayed_work(ipoib_workqueue, &priv->ah_reap_task,
+ queue_delayed_work(priv->wq, &priv->ah_reap_task,
round_jiffies_relative(HZ));
}
round_jiffies_relative(HZ));
}
cancel_delayed_work(&priv->ah_reap_task);
if (flush)
cancel_delayed_work(&priv->ah_reap_task);
if (flush)
- flush_workqueue(ipoib_workqueue);
+ flush_workqueue(priv->wq);
ipoib_reap_ah(&priv->ah_reap_task.work);
}
ipoib_reap_ah(&priv->ah_reap_task.work);
}
}
clear_bit(IPOIB_STOP_REAPER, &priv->flags);
}
clear_bit(IPOIB_STOP_REAPER, &priv->flags);
- queue_delayed_work(ipoib_workqueue, &priv->ah_reap_task,
+ queue_delayed_work(priv->wq, &priv->ah_reap_task,
round_jiffies_relative(HZ));
if (!test_and_set_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
round_jiffies_relative(HZ));
if (!test_and_set_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
- queue_work(ipoib_workqueue, &priv->restart_task);
+ queue_work(priv->wq, &priv->restart_task);
}
static int ipoib_get_iflink(const struct net_device *dev)
}
static int ipoib_get_iflink(const struct net_device *dev)
__ipoib_reap_neigh(priv);
if (!test_bit(IPOIB_STOP_NEIGH_GC, &priv->flags))
__ipoib_reap_neigh(priv);
if (!test_bit(IPOIB_STOP_NEIGH_GC, &priv->flags))
- queue_delayed_work(ipoib_workqueue, &priv->neigh_reap_task,
+ queue_delayed_work(priv->wq, &priv->neigh_reap_task,
/* start garbage collection */
clear_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
/* start garbage collection */
clear_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
- queue_delayed_work(ipoib_workqueue, &priv->neigh_reap_task,
+ queue_delayed_work(priv->wq, &priv->neigh_reap_task,
arp_tbl.gc_interval);
return 0;
arp_tbl.gc_interval);
return 0;
register_failed:
ib_unregister_event_handler(&priv->event_handler);
register_failed:
ib_unregister_event_handler(&priv->event_handler);
+ flush_workqueue(ipoib_workqueue);
/* Stop GC if started before flush */
set_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
cancel_delayed_work(&priv->neigh_reap_task);
/* Stop GC if started before flush */
set_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
cancel_delayed_work(&priv->neigh_reap_task);
- flush_workqueue(ipoib_workqueue);
+ flush_workqueue(priv->wq);
event_failed:
ipoib_dev_cleanup(priv->dev);
event_failed:
ipoib_dev_cleanup(priv->dev);
list_for_each_entry_safe(priv, tmp, dev_list, list) {
ib_unregister_event_handler(&priv->event_handler);
list_for_each_entry_safe(priv, tmp, dev_list, list) {
ib_unregister_event_handler(&priv->event_handler);
+ flush_workqueue(ipoib_workqueue);
rtnl_lock();
dev_change_flags(priv->dev, priv->dev->flags & ~IFF_UP);
rtnl_lock();
dev_change_flags(priv->dev, priv->dev->flags & ~IFF_UP);
/* Stop GC */
set_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
cancel_delayed_work(&priv->neigh_reap_task);
/* Stop GC */
set_bit(IPOIB_STOP_NEIGH_GC, &priv->flags);
cancel_delayed_work(&priv->neigh_reap_task);
- flush_workqueue(ipoib_workqueue);
+ flush_workqueue(priv->wq);
unregister_netdev(priv->dev);
free_netdev(priv->dev);
unregister_netdev(priv->dev);
free_netdev(priv->dev);
- * We create our own workqueue mainly because we want to be
- * able to flush it when devices are being removed. We can't
- * use schedule_work()/flush_scheduled_work() because both
- * unregister_netdev() and linkwatch_event take the rtnl lock,
- * so flush_scheduled_work() can deadlock during device
- * removal.
+ * We create a global workqueue here that is used for all flush
+ * operations. However, if you attempt to flush a workqueue
+ * from a task on that same workqueue, it deadlocks the system.
+ * We want to be able to flush the tasks associated with a
+ * specific net device, so we also create a workqueue for each
+ * netdevice. We queue up the tasks for that device only on
+ * its private workqueue, and we only queue up flush events
+ * on our global flush workqueue. This avoids the deadlocks.
- ipoib_workqueue = create_singlethread_workqueue("ipoib");
+ ipoib_workqueue = create_singlethread_workqueue("ipoib_flush");
if (!ipoib_workqueue) {
ret = -ENOMEM;
goto err_fs;
if (!ipoib_workqueue) {
ret = -ENOMEM;
goto err_fs;
mcast->backoff = 1;
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
mcast->backoff = 1;
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
- queue_delayed_work(ipoib_workqueue,
- &priv->mcast_task, 0);
+ queue_delayed_work(priv->wq, &priv->mcast_task, 0);
mutex_unlock(&mcast_mutex);
/*
mutex_unlock(&mcast_mutex);
/*
- * Defer carrier on work to ipoib_workqueue to avoid a
+ * Defer carrier on work to priv->wq to avoid a
* deadlock on rtnl_lock here.
*/
if (mcast == priv->broadcast)
* deadlock on rtnl_lock here.
*/
if (mcast == priv->broadcast)
- queue_work(ipoib_workqueue, &priv->carrier_on_task);
+ queue_work(priv->wq, &priv->carrier_on_task);
mutex_lock(&mcast_mutex);
spin_lock_irq(&priv->lock);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
mutex_lock(&mcast_mutex);
spin_lock_irq(&priv->lock);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
- queue_delayed_work(ipoib_workqueue, &priv->mcast_task,
+ queue_delayed_work(priv->wq, &priv->mcast_task,
mcast->backoff * HZ);
spin_unlock_irq(&priv->lock);
mutex_unlock(&mcast_mutex);
mcast->backoff * HZ);
spin_unlock_irq(&priv->lock);
mutex_unlock(&mcast_mutex);
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
- queue_delayed_work(ipoib_workqueue,
- &priv->mcast_task,
+ queue_delayed_work(priv->wq, &priv->mcast_task,
mcast->backoff * HZ);
mutex_unlock(&mcast_mutex);
}
mcast->backoff * HZ);
mutex_unlock(&mcast_mutex);
}
ipoib_warn(priv, "failed to allocate broadcast group\n");
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
ipoib_warn(priv, "failed to allocate broadcast group\n");
mutex_lock(&mcast_mutex);
if (test_bit(IPOIB_MCAST_RUN, &priv->flags))
- queue_delayed_work(ipoib_workqueue,
- &priv->mcast_task, HZ);
+ queue_delayed_work(priv->wq, &priv->mcast_task,
+ HZ);
mutex_unlock(&mcast_mutex);
return;
}
mutex_unlock(&mcast_mutex);
return;
}
mutex_lock(&mcast_mutex);
if (!test_and_set_bit(IPOIB_MCAST_RUN, &priv->flags))
mutex_lock(&mcast_mutex);
if (!test_and_set_bit(IPOIB_MCAST_RUN, &priv->flags))
- queue_delayed_work(ipoib_workqueue, &priv->mcast_task, 0);
+ queue_delayed_work(priv->wq, &priv->mcast_task, 0);
mutex_unlock(&mcast_mutex);
return 0;
mutex_unlock(&mcast_mutex);
return 0;
mutex_unlock(&mcast_mutex);
if (flush)
mutex_unlock(&mcast_mutex);
if (flush)
- flush_workqueue(ipoib_workqueue);
+ flush_workqueue(priv->wq);
+ /*
+ * the various IPoIB tasks assume they will never race against
+ * themselves, so always use a single thread workqueue
+ */
+ priv->wq = create_singlethread_workqueue("ipoib_wq");
+ if (!priv->wq) {
+ printk(KERN_WARNING "ipoib: failed to allocate device WQ\n");
+ goto out_free_mr;
+ }
+
size = ipoib_recvq_size + 1;
ret = ipoib_cm_dev_init(dev);
if (!ret) {
size = ipoib_recvq_size + 1;
ret = ipoib_cm_dev_init(dev);
if (!ret) {
size += ipoib_recvq_size + 1; /* 1 extra for rx_drain_qp */
else
size += ipoib_recvq_size * ipoib_max_conn_qp;
size += ipoib_recvq_size + 1; /* 1 extra for rx_drain_qp */
else
size += ipoib_recvq_size * ipoib_max_conn_qp;
+ } else
+ goto out_free_wq;
priv->recv_cq = ib_create_cq(priv->ca, ipoib_ib_completion, NULL, dev, size, 0);
if (IS_ERR(priv->recv_cq)) {
printk(KERN_WARNING "%s: failed to create receive CQ\n", ca->name);
priv->recv_cq = ib_create_cq(priv->ca, ipoib_ib_completion, NULL, dev, size, 0);
if (IS_ERR(priv->recv_cq)) {
printk(KERN_WARNING "%s: failed to create receive CQ\n", ca->name);
+ goto out_cm_dev_cleanup;
}
priv->send_cq = ib_create_cq(priv->ca, ipoib_send_comp_handler, NULL,
}
priv->send_cq = ib_create_cq(priv->ca, ipoib_send_comp_handler, NULL,
out_free_recv_cq:
ib_destroy_cq(priv->recv_cq);
out_free_recv_cq:
ib_destroy_cq(priv->recv_cq);
+out_cm_dev_cleanup:
+ ipoib_cm_dev_cleanup(dev);
+
+out_free_wq:
+ destroy_workqueue(priv->wq);
+ priv->wq = NULL;
+
out_free_mr:
ib_dereg_mr(priv->mr);
out_free_mr:
ib_dereg_mr(priv->mr);
- ipoib_cm_dev_cleanup(dev);
out_free_pd:
ib_dealloc_pd(priv->pd);
out_free_pd:
ib_dealloc_pd(priv->pd);
ipoib_cm_dev_cleanup(dev);
ipoib_cm_dev_cleanup(dev);
+ if (priv->wq) {
+ flush_workqueue(priv->wq);
+ destroy_workqueue(priv->wq);
+ priv->wq = NULL;
+ }
+
if (ib_dereg_mr(priv->mr))
ipoib_warn(priv, "ib_dereg_mr failed\n");
if (ib_dealloc_pd(priv->pd))
ipoib_warn(priv, "ib_dealloc_pd failed\n");
if (ib_dereg_mr(priv->mr))
ipoib_warn(priv, "ib_dereg_mr failed\n");
if (ib_dealloc_pd(priv->pd))
ipoib_warn(priv, "ib_dealloc_pd failed\n");
}
void ipoib_event(struct ib_event_handler *handler,
}
void ipoib_event(struct ib_event_handler *handler,