From a9312ae89324438b0edc554eb36c3ec6bf927d04 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sun, 17 Aug 2008 21:51:03 -0700 Subject: pkt_sched: Add 'deactivated' state. This new state lets dev_deactivate() mark a qdisc as having been deactivated. dev_queue_xmit() and ing_filter() check for this bit and do not try to process the qdisc if the bit is set. dev_deactivate() polls the qdisc after setting the bit, waiting for both __QDISC_STATE_RUNNING and __QDISC_STATE_SCHED to clear. This isn't perfect yet, but subsequent changesets will make it so. This part is just one piece of the puzzle. Signed-off-by: David S. Miller --- net/core/dev.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'net/core/dev.c') diff --git a/net/core/dev.c b/net/core/dev.c index 600bb23c4c2..d9e31f63ade 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1800,6 +1800,12 @@ gso: spin_lock(root_lock); + if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) { + spin_unlock(root_lock); + rc = NET_XMIT_DROP; + goto out_kfree_skb; + } + rc = qdisc_enqueue_root(skb, q); qdisc_run(q); @@ -2084,7 +2090,8 @@ static int ing_filter(struct sk_buff *skb) q = rxq->qdisc; if (q != &noop_qdisc) { spin_lock(qdisc_lock(q)); - result = qdisc_enqueue_root(skb, q); + if (likely(!test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) + result = qdisc_enqueue_root(skb, q); spin_unlock(qdisc_lock(q)); } -- cgit v1.2.3-70-g09d2 From def82a1db1fdc4f861c77009e2ee86870c3743b0 Mon Sep 17 00:00:00 2001 From: Jarek Poplawski Date: Sun, 17 Aug 2008 21:54:43 -0700 Subject: net: Change handling of the __QDISC_STATE_SCHED flag in net_tx_action(). Change handling of the __QDISC_STATE_SCHED flag in net_tx_action() to enable proper control in dev_deactivate(). Now, if this flag is seen as unset under root_lock means a qdisc can't be netif_scheduled. Signed-off-by: Jarek Poplawski Signed-off-by: David S. Miller --- net/core/dev.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) (limited to 'net/core/dev.c') diff --git a/net/core/dev.c b/net/core/dev.c index d9e31f63ade..819f0175bdc 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1339,19 +1339,23 @@ static void dev_queue_xmit_nit(struct sk_buff *skb, struct net_device *dev) } -void __netif_schedule(struct Qdisc *q) +static inline void __netif_reschedule(struct Qdisc *q) { - if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state)) { - struct softnet_data *sd; - unsigned long flags; + struct softnet_data *sd; + unsigned long flags; - local_irq_save(flags); - sd = &__get_cpu_var(softnet_data); - q->next_sched = sd->output_queue; - sd->output_queue = q; - raise_softirq_irqoff(NET_TX_SOFTIRQ); - local_irq_restore(flags); - } + local_irq_save(flags); + sd = &__get_cpu_var(softnet_data); + q->next_sched = sd->output_queue; + sd->output_queue = q; + raise_softirq_irqoff(NET_TX_SOFTIRQ); + local_irq_restore(flags); +} + +void __netif_schedule(struct Qdisc *q) +{ + if (!test_and_set_bit(__QDISC_STATE_SCHED, &q->state)) + __netif_reschedule(q); } EXPORT_SYMBOL(__netif_schedule); @@ -1980,15 +1984,15 @@ static void net_tx_action(struct softirq_action *h) head = head->next_sched; - smp_mb__before_clear_bit(); - clear_bit(__QDISC_STATE_SCHED, &q->state); - root_lock = qdisc_lock(q); if (spin_trylock(root_lock)) { + smp_mb__before_clear_bit(); + clear_bit(__QDISC_STATE_SCHED, + &q->state); qdisc_run(q); spin_unlock(root_lock); } else { - __netif_schedule(q); + __netif_reschedule(q); } } } -- cgit v1.2.3-70-g09d2 From 96d203169d1d851ac1468f7d4459a09581be364c Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Sun, 17 Aug 2008 23:37:16 -0700 Subject: pkt_sched: Fix missed RCU unlock in dev_queue_xmit() Noticed by Jarek Poplawski. Signed-off-by: David S. Miller --- net/core/dev.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'net/core/dev.c') diff --git a/net/core/dev.c b/net/core/dev.c index 819f0175bdc..8d133802372 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1805,14 +1805,12 @@ gso: spin_lock(root_lock); if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) { - spin_unlock(root_lock); + kfree_skb(skb); rc = NET_XMIT_DROP; - goto out_kfree_skb; + } else { + rc = qdisc_enqueue_root(skb, q); + qdisc_run(q); } - - rc = qdisc_enqueue_root(skb, q); - qdisc_run(q); - spin_unlock(root_lock); goto out; -- cgit v1.2.3-70-g09d2 From 195648bbc5ae0848e82f771ecf4cd7497054c212 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Tue, 19 Aug 2008 04:00:36 -0700 Subject: pkt_sched: Prevent livelock in TX queue running. If dev_deactivate() is trying to quiesce the queue, it is theoretically possible for another cpu to livelock trying to process that queue. This happens because dev_deactivate() grabs the queue spinlock as it checks the queue state, whereas net_tx_action() does a trylock and reschedules the qdisc if it hits the lock. This breaks the livelock by adding a check on __QDISC_STATE_DEACTIVATED to net_tx_action() when the trylock fails. Based upon feedback from Herbert Xu and Jarek Poplawski. Signed-off-by: David S. Miller --- net/core/dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'net/core/dev.c') diff --git a/net/core/dev.c b/net/core/dev.c index 8d133802372..60c51f76588 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -1990,7 +1990,9 @@ static void net_tx_action(struct softirq_action *h) qdisc_run(q); spin_unlock(root_lock); } else { - __netif_reschedule(q); + if (!test_bit(__QDISC_STATE_DEACTIVATED, + &q->state)) + __netif_reschedule(q); } } } -- cgit v1.2.3-70-g09d2