From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: [PATCH 2.6 PKT_SCHED]: Fix rcu_assign_pointer fallout, use it in the right place Date: Fri, 05 Nov 2004 22:45:46 +0100 Message-ID: <418BF48A.5060707@trash.net> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="------------010107060405000301040302" Cc: netdev@oss.sgi.com Return-path: To: "David S. Miller" Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org This is a multi-part message in MIME format. --------------010107060405000301040302 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit The patch "RCU: use rcu_assign_pointer()" http://linux.bkbits.net:8080/linux-2.6/diffs/net/sched/sch_api.c@1.39?nav=index.html|src/net/|src/net|src/net/sched|related/net/sched/sch_api.c|cset@1.2287 changed a list_add_tail to list_add_tail_rcu in qdisc_create. It's dev->qdisc not dev->qdisc_list that is protected by RCU, this patch reverts that change. It also removes a misleading comment and replaces the smp_wmb in qdisc_create_dflt by rcu_assign_pointer in dev_activate to document more clearly what is protected. Regards Patrick --------------010107060405000301040302 Content-Type: text/plain; name="x" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="x" # This is a BitKeeper generated diff -Nru style patch. # # ChangeSet # 2004/11/05 22:14:18+01:00 kaber@coreworks.de # [PKT_SCHED]: Fix rcu_assign_pointer fallout, use it in the right place # # Signed-off-by: Patrick McHardy # # net/sched/sch_generic.c # 2004/11/05 22:14:08+01:00 kaber@coreworks.de +5 -7 # [PKT_SCHED]: Fix rcu_assign_pointer fallout, use it in the right place # # Signed-off-by: Patrick McHardy # # net/sched/sch_api.c # 2004/11/05 22:14:08+01:00 kaber@coreworks.de +2 -4 # [PKT_SCHED]: Fix rcu_assign_pointer fallout, use it in the right place # # Signed-off-by: Patrick McHardy # diff -Nru a/net/sched/sch_api.c b/net/sched/sch_api.c --- a/net/sched/sch_api.c 2004-11-05 22:29:06 +01:00 +++ b/net/sched/sch_api.c 2004-11-05 22:29:06 +01:00 @@ -451,11 +451,9 @@ else sch->handle = handle; - /* enqueue is accessed locklessly - make sure it's visible - * before we set a netdevice's qdisc pointer to sch */ if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS-1])) == 0) { qdisc_lock_tree(dev); - list_add_tail_rcu(&sch->list, &dev->qdisc_list); + list_add_tail(&sch->list, &dev->qdisc_list); qdisc_unlock_tree(dev); #ifdef CONFIG_NET_ESTIMATOR diff -Nru a/net/sched/sch_generic.c b/net/sched/sch_generic.c --- a/net/sched/sch_generic.c 2004-11-05 22:29:06 +01:00 +++ b/net/sched/sch_generic.c 2004-11-05 22:29:06 +01:00 @@ -436,9 +436,6 @@ dev_hold(dev); sch->stats_lock = &dev->queue_lock; atomic_set(&sch->refcnt, 1); - /* enqueue is accessed locklessly - make sure it's visible - * before we set a netdevice's qdisc pointer to sch */ - smp_wmb(); if (!ops->init || ops->init(sch, NULL) == 0) return sch; @@ -519,7 +516,8 @@ } spin_lock_bh(&dev->queue_lock); - if ((dev->qdisc = dev->qdisc_sleeping) != &noqueue_qdisc) { + rcu_assign_pointer(dev->qdisc, dev->qdisc_sleeping); + if (dev->qdisc != &noqueue_qdisc) { dev->trans_start = jiffies; dev_watchdog_up(dev); } --------------010107060405000301040302--