Patch "net: sched: drop qdisc_reset from dev_graft_qdisc" has been added to the 4.15-stable tree
Subsystems (3)
This is a note to let you know that I've just added the patch titled
net: sched: drop qdisc_reset from dev_graft_qdisc
to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-sched-drop-qdisc_reset-from-dev_graft_qdisc.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From foo@baz Fri Mar 16 15:11:08 CET 2018
From: John Fastabend <[email protected]>
Date: Thu, 7 Dec 2017 09:56:04 -0800
Subject: net: sched: drop qdisc_reset from dev_graft_qdisc
From: John Fastabend <[email protected]>
[ Upstream commit 7bbde83b1860c28a1cc35516352c4e7e5172c29a ]
In qdisc_graft_qdisc a "new" qdisc is attached and the 'qdisc_destroy' operation is called on the old qdisc. The destroy operation will wait a rcu grace period and call qdisc_rcu_free(). At which point gso_cpu_skb is free'd along with all stats so no need to zero stats and gso_cpu_skb from the graft operation itself.
Further after dropping the qdisc locks we can not continue to call qdisc_reset before waiting an rcu grace period so that the qdisc is detached from all cpus. By removing the qdisc_reset() here we get the correct property of waiting an rcu grace period and letting the qdisc_destroy operation clean up the qdisc correctly.
Note, a refcnt greater than 1 would cause the destroy operation to be aborted however if this ever happened the reference to the qdisc would be lost and we would have a memory leak.
--- net/sched/sch_generic.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-)
net/sched/sch_generic.c +19 -9
@@ -762,10 +762,6 @@ struct Qdisc *dev_graft_qdisc(struct net root_lock =qdisc_lock (oqdisc);spin_lock_bh (root_lock); -/* Prune old scheduler */ -if (oqdisc &&refcount_read (&oqdisc->refcnt) <=1 ) -qdisc_reset (oqdisc); -/* ... and graft new one */ if (qdisc ==NULL ) qdisc = &noop_qdisc;
@@ -916,6 +912,16 @@ static bool some_qdisc_is_busy(struct nereturn false; } +static void dev_qdisc_reset (struct net_device *dev, +struct netdev_queue *dev_queue, +void *none) +{ +struct Qdisc *qdisc = dev_queue->qdisc_sleeping; + +if (qdisc) +qdisc_reset (qdisc); +} +/** * dev_deactivate_many - deactivate transmissions on several devices * @head: list of devices to deactivate
@@ -926,7 +932,6 @@ static bool some_qdisc_is_busy(struct nevoid dev_deactivate_many (struct list_head *head) {struct net_device *dev; -bool sync_needed = false;list_for_each_entry (dev, head, close_list) { netdev_for_each_tx_queue(dev, dev_deactivate_queue,
@@ -936,20 +941,25 @@ void dev_deactivate_many(struct list_hea &noop_qdisc);dev_watchdog_down (dev); - sync_needed |= !dev->dismantle; }/* Wait for outstanding qdisc-less dev_queue_xmit calls. * This is avoided if all devices are in dismantle phase : * Caller will call synchronize_net() for us */ -if (sync_needed) -synchronize_net (); +synchronize_net ();/* Wait for outstanding qdisc_run calls. */ -list_for_each_entry (dev, head, close_list) +list_for_each_entry (dev, head, close_list) {while (some_qdisc_is_busy (dev))yield (); +/* The new qdisc is assigned at this point so we can safely +* unwind stale skb lists and qdisc statistics +*/ +netdev_for_each_tx_queue (dev, dev_qdisc_reset,NULL ); +if (dev_ingress_queue (dev)) +dev_qdisc_reset (dev,dev_ingress_queue (dev),NULL ); + } }void dev_deactivate (struct net_device *dev)
Patches currently in stable-queue which might be from [email protected] are
queue-4.15/net-sched-drop-qdisc_reset-from-dev_graft_qdisc.patch queue-4.15/bpf-fix-stack-state-printing-in-verifier-log.patch