From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: [PATCH take 2] pkt_sched: Fix qdisc list locking Date: Fri, 22 Aug 2008 09:27:30 +0000 Message-ID: <20080822092729.GA14729@ff.dom.local> References: <20080821124834.GA8794@gondor.apana.org.au> <20080821204052.GB2665@ami.dom.local> <20080821222446.GF14521@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev@vger.kernel.org, denys@visp.net.lb To: Herbert Xu Return-path: Received: from nf-out-0910.google.com ([64.233.182.188]:56371 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752577AbYHVJ1i (ORCPT ); Fri, 22 Aug 2008 05:27:38 -0400 Received: by nf-out-0910.google.com with SMTP id d3so172955nfc.21 for ; Fri, 22 Aug 2008 02:27:35 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20080821222446.GF14521@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: I made an error in the name of this new lock in the changlog, so I decided to fix this in ...the patch. Sorry, Jarek P. ---------------> (take 2) pkt_sched: Fix qdisc list locking Since some qdiscs call qdisc_tree_decrease_qlen() (so qdisc_lookup()) without rtnl_lock(), adding and deleting from a qdisc list needs additional locking. This patch adds global spinlock qdisc_list_lock and wrapper functions for modifying the list. It is considered as a temporary solution until hfsc_dequeue(), netem_dequeue() and tbf_dequeue() (or qdisc_tree_decrease_qlen()) are redone. With feedback from Herbert Xu and David S. Miller. Signed-off-by: Jarek Poplawski --- include/net/pkt_sched.h | 1 + net/sched/sch_api.c | 44 +++++++++++++++++++++++++++++++++++++++----- net/sched/sch_generic.c | 5 ++--- 3 files changed, 42 insertions(+), 8 deletions(-) diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index 853fe83..b786a5b 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -78,6 +78,7 @@ extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, extern int register_qdisc(struct Qdisc_ops *qops); extern int unregister_qdisc(struct Qdisc_ops *qops); +extern void qdisc_list_del(struct Qdisc *q); extern struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle); extern struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle); extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index 45f442d..e7fb9e0 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -199,19 +199,53 @@ 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); + 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); + list_del(&q->list); + spin_unlock_bh(&qdisc_list_lock); + } +} +EXPORT_SYMBOL(qdisc_list_del); + 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 *q, *txq_root = txq->qdisc_sleeping; + struct Qdisc *txq_root = txq->qdisc_sleeping; q = qdisc_match_from_root(txq_root, handle); if (q) - return q; + goto unlock; } - return qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle); + + q = qdisc_match_from_root(dev->rx_queue.qdisc_sleeping, handle); + +unlock: + spin_unlock_bh(&qdisc_list_lock); + + return q; } static struct Qdisc *qdisc_leaf(struct Qdisc *p, u32 classid) @@ -810,8 +844,8 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue, goto err_out3; } } - if ((parent != TC_H_ROOT) && !(sch->flags & TCQ_F_INGRESS)) - list_add_tail(&sch->list, &dev_queue->qdisc_sleeping->list); + + qdisc_list_add(sch); return sch; } diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index c3ed4d4..5f0ade7 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -526,10 +526,9 @@ void qdisc_destroy(struct Qdisc *qdisc) !atomic_dec_and_test(&qdisc->refcnt)) return; - if (qdisc->parent) - list_del(&qdisc->list); - #ifdef CONFIG_NET_SCHED + qdisc_list_del(qdisc); + qdisc_put_stab(qdisc->stab); #endif gen_kill_estimator(&qdisc->bstats, &qdisc->rate_est);