| Message ID | 20081125112941.GA8136@ff.dom.local |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
Jarek Poplawski wrote: > After implementing qdisc->ops->peek() there is no more calling > qdisc_tree_decrease_qlen() without rtnl_lock(), so qdisc_list_lock > added by commit: f6e0b239a2657ea8cb67f0d83d0bfdbfd19a481b "pkt_sched: > Fix qdisc list locking" can be removed. I might be misunderstanding something, but qdisc_tree_decrease_qlen() doesn't need rtnl_lock() but the sch_tree_lock() since it changes q.qlen. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Patrick McHardy wrote: > Jarek Poplawski wrote: >> After implementing qdisc->ops->peek() there is no more calling >> qdisc_tree_decrease_qlen() without rtnl_lock(), so qdisc_list_lock >> added by commit: f6e0b239a2657ea8cb67f0d83d0bfdbfd19a481b "pkt_sched: >> Fix qdisc list locking" can be removed. > > I might be misunderstanding something, but qdisc_tree_decrease_qlen() > doesn't need rtnl_lock() but the sch_tree_lock() since it changes > q.qlen. OK I see now, rtnl_lock() was taken to protect the parent qdisc lookup. In that case it seems fine, all callers are holding both sch_tree_lock() and rtnl_lock(). -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Patrick McHardy <kaber@trash.net> Date: Tue, 25 Nov 2008 12:46:25 +0100 > Patrick McHardy wrote: > > Jarek Poplawski wrote: > >> After implementing qdisc->ops->peek() there is no more calling > >> qdisc_tree_decrease_qlen() without rtnl_lock(), so qdisc_list_lock > >> added by commit: f6e0b239a2657ea8cb67f0d83d0bfdbfd19a481b "pkt_sched: > >> Fix qdisc list locking" can be removed. > > I might be misunderstanding something, but qdisc_tree_decrease_qlen() > > doesn't need rtnl_lock() but the sch_tree_lock() since it changes > > q.qlen. > > OK I see now, rtnl_lock() was taken to protect the parent qdisc lookup. > In that case it seems fine, all callers are holding both sch_tree_lock() > and rtnl_lock(). :-) I've applied Jarek's patch. Thanks! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 1ef25e6..3fcfd4e 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -204,28 +204,16 @@ struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle) return NULL; } -/* - * This lock is needed until some qdiscs stop calling qdisc_tree_decrease_qlen() - * without rtnl_lock(); currently hfsc_dequeue(), netem_dequeue(), tbf_dequeue() - */ -static DEFINE_SPINLOCK(qdisc_list_lock); - static void qdisc_list_add(struct Qdisc *q) { - if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) { - spin_lock_bh(&qdisc_list_lock); + if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) list_add_tail(&q->list, &qdisc_root_sleeping(q)->list); - spin_unlock_bh(&qdisc_list_lock); - } } void qdisc_list_del(struct Qdisc *q) { - if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) { - spin_lock_bh(&qdisc_list_lock); + if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS)) list_del(&q->list); - spin_unlock_bh(&qdisc_list_lock); - } } EXPORT_SYMBOL(qdisc_list_del); @@ -234,22 +222,17 @@ struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle) unsigned int i; struct Qdisc *q; - spin_lock_bh(&qdisc_list_lock); - for (i = 0; i < dev->num_tx_queues; i++) { struct netdev_queue *txq = netdev_get_tx_queue(dev, i); struct Qdisc *txq_root = txq->qdisc_sleeping; q = qdisc_match_from_root(txq_root, handle); if (q) - goto unlock; + goto out; } q = qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle); - -unlock: - spin_unlock_bh(&qdisc_list_lock); - +out: return q; }
After implementing qdisc->ops->peek() there is no more calling qdisc_tree_decrease_qlen() without rtnl_lock(), so qdisc_list_lock added by commit: f6e0b239a2657ea8cb67f0d83d0bfdbfd19a481b "pkt_sched: Fix qdisc list locking" can be removed. Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> --- net/sched/sch_api.c | 25 ++++--------------------- 1 files changed, 4 insertions(+), 21 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html