Messages in this thread Patch in this message | | | Date | Thu, 2 Feb 2006 12:27:31 +0100 | From | Ingo Molnar <> | Subject | Re: [lock validator] inet6_destroy_sock(): soft-safe -> soft-unsafe lock dependency |
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* Ingo Molnar <mingo@elte.hu> wrote:
> hm, i got a new one: > > ============================================ > [ BUG: circular locking deadlock detected! ] > -------------------------------------------- > sshd/28997 is trying to acquire lock: > (&sk->sk_lock.slock){-+}, at: [<c0c6be28>] packet_rcv+0xbf/0x34b > > but task is already holding lock: > (&dev->xmit_lock){-+}, at: [<c0bb04ec>] qdisc_restart+0x46/0x207 > > which lock already depends on the new lock, > which could lead to circular deadlocks! > > the dependency chain (in reverse order) is: > -> #2 (&dev->xmit_lock){-+}: [<c0bb04ec>] qdisc_restart+0x46/0x207 > -> #1 (&dev->queue_lock){-+}: [<c0b98137>] dev_queue_xmit+0xc3/0x21e > -> #0 (&sk->sk_lock.slock){-+}: [<c0c6be28>] packet_rcv+0xbf/0x34b
i think this might be a false positive, caused by my (ill-advised) change below? [i did the change to clean up an unlock ordering assymetry, but apparently i thus also introduced the xmit_lock -> queue_lock dependency.]
Ingo
Index: linux/net/sched/sch_generic.c =================================================================== --- linux.orig/net/sched/sch_generic.c +++ linux/net/sched/sch_generic.c @@ -98,6 +98,8 @@ int qdisc_restart(struct net_device *dev /* Dequeue packet */ if ((skb = q->dequeue(q)) != NULL) { unsigned nolock = (dev->features & NETIF_F_LLTX); + /* release queue */ + spin_unlock(&dev->queue_lock); /* * When the driver has LLTX set it does its own locking * in start_xmit. No need to add additional overhead by @@ -121,9 +123,11 @@ int qdisc_restart(struct net_device *dev kfree_skb(skb); if (net_ratelimit()) printk(KERN_DEBUG "Dead loop on netdevice %s, fix it urgently!\n", dev->name); + spin_lock(&dev->queue_lock); return -1; } __get_cpu_var(netdev_rx_stat).cpu_collision++; + spin_lock(&dev->queue_lock); goto requeue; } /* Remember that the driver is grabbed by us. */ @@ -131,8 +135,6 @@ int qdisc_restart(struct net_device *dev } { - /* And release queue */ - spin_unlock(&dev->queue_lock); if (!netif_queue_stopped(dev)) { int ret; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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