Patchwork [take2] pkt_sched: Fix TX state checking in qdisc_run()

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Submitter Jarek Poplawski
Date Sept. 19, 2008, 2:44 p.m.
Message ID <20080919144450.GA2646@ami.dom.local>
Download mbox | patch
Permalink /patch/629/
State RFC
Delegated to: David Miller
Headers show

Comments

Jarek Poplawski - Sept. 19, 2008, 2:44 p.m.
Alas this time the changelog needs more details.

Sorry,
Jarek P.
-----------------> (take 2)

pkt_sched: Fix TX state checking in qdisc_run()

Current check wrongly uses the state of the first tx queue for all tx
queues in case of non-default qdiscs. This patch brings back per dev
__LINK_STATE_XOFF flag, which is set when all tx queues are stopped.
This check is needed in qdisc_run() to avoid useless __netif_schedule()
calls. The wrongness of this check was first noticed by Herbert Xu.

Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Jarek Poplawski - Sept. 19, 2008, 5:49 p.m.
Jarek Poplawski wrote, On 09/19/2008 04:44 PM:

> Alas this time the changelog needs more details.
> 
> Sorry,
> Jarek P.
> -----------------> (take 2)
> 
> pkt_sched: Fix TX state checking in qdisc_run()


David,

After reading Alexander's opinion I withdaw this patch (take 1 & 2)
as well.

Sorry,
Jarek P.
David Miller - Sept. 21, 2008, 5:18 a.m.
From: Jarek Poplawski <jarkao2@gmail.com>
Date: Fri, 19 Sep 2008 16:44:50 +0200

> pkt_sched: Fix TX state checking in qdisc_run()
> 
> Current check wrongly uses the state of the first tx queue for all tx
> queues in case of non-default qdiscs. This patch brings back per dev
> __LINK_STATE_XOFF flag, which is set when all tx queues are stopped.
> This check is needed in qdisc_run() to avoid useless __netif_schedule()
> calls. The wrongness of this check was first noticed by Herbert Xu.
> 
> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>

I'm dropping this and the patches in the ->smart_requeue thread as well.

It simply isn't crystal clear how to proceed at this point.
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Patch

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 488c56e..dc76e4b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -271,6 +271,7 @@  struct header_ops {
 
 enum netdev_state_t
 {
+	__LINK_STATE_XOFF,
 	__LINK_STATE_START,
 	__LINK_STATE_PRESENT,
 	__LINK_STATE_NOCARRIER,
@@ -1043,6 +1044,7 @@  static inline void netif_tx_wake_queue(struct netdev_queue *dev_queue)
 static inline void netif_wake_queue(struct net_device *dev)
 {
 	netif_tx_wake_queue(netdev_get_tx_queue(dev, 0));
+	clear_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
 static inline void netif_tx_wake_all_queues(struct net_device *dev)
@@ -1053,6 +1055,7 @@  static inline void netif_tx_wake_all_queues(struct net_device *dev)
 		struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
 		netif_tx_wake_queue(txq);
 	}
+	clear_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
 static inline void netif_tx_stop_queue(struct netdev_queue *dev_queue)
@@ -1069,6 +1072,7 @@  static inline void netif_tx_stop_queue(struct netdev_queue *dev_queue)
  */
 static inline void netif_stop_queue(struct net_device *dev)
 {
+	set_bit(__LINK_STATE_XOFF, &dev->state);
 	netif_tx_stop_queue(netdev_get_tx_queue(dev, 0));
 }
 
@@ -1076,6 +1080,7 @@  static inline void netif_tx_stop_all_queues(struct net_device *dev)
 {
 	unsigned int i;
 
+	set_bit(__LINK_STATE_XOFF, &dev->state);
 	for (i = 0; i < dev->num_tx_queues; i++) {
 		struct netdev_queue *txq = netdev_get_tx_queue(dev, i);
 		netif_tx_stop_queue(txq);
@@ -1095,7 +1100,7 @@  static inline int netif_tx_queue_stopped(const struct netdev_queue *dev_queue)
  */
 static inline int netif_queue_stopped(const struct net_device *dev)
 {
-	return netif_tx_queue_stopped(netdev_get_tx_queue(dev, 0));
+	return test_bit(__LINK_STATE_XOFF, &dev->state);
 }
 
 static inline int netif_tx_queue_frozen(const struct netdev_queue *dev_queue)
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index b786a5b..1718a60 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -90,9 +90,7 @@  extern void __qdisc_run(struct Qdisc *q);
 
 static inline void qdisc_run(struct Qdisc *q)
 {
-	struct netdev_queue *txq = q->dev_queue;
-
-	if (!netif_tx_queue_stopped(txq) &&
+	if (!netif_queue_stopped(qdisc_dev(q)) &&
 	    !test_and_set_bit(__QDISC_STATE_RUNNING, &q->state))
 		__qdisc_run(q);
 }