kernel.git/net/sched/sch_generic.c, branch linux-5.0.y

net: sched: put back q.qlen into a single location

2019-03-10T06:08:59Z

[ Upstream commit 46b1c18f9deb326a7e18348e668e4c7ab7c7458b ] In the series fc8b81a5981f ("Merge branch 'lockless-qdisc-series'") John made the assumption that the data path had no need to read the qdisc qlen (number of packets in the qdisc). It is true when pfifo_fast is used as the root qdisc, or as direct MQ/MQPRIO children. But pfifo_fast can be used as leaf in class full qdiscs, and existing logic needs to access the child qlen in an efficient way. HTB breaks badly, since it uses cl->leaf.q->q.qlen in : htb_activate() -> WARN_ON() htb_dequeue_tree() to decide if a class can be htb_deactivated when it has no more packets. HFSC, DRR, CBQ, QFQ have similar issues, and some calls to qdisc_tree_reduce_backlog() also read q.qlen directly. Using qdisc_qlen_sum() (which iterates over all possible cpus) in the data path is a non starter. It seems we have to put back qlen in a central location, at least for stable kernels. For all qdisc but pfifo_fast, qlen is guarded by the qdisc lock, so the existing q.qlen{++|--} are correct. For 'lockless' qdisc (pfifo_fast so far), we need to use atomic_{inc|dec}() because the spinlock might be not held (for example from pfifo_fast_enqueue() and pfifo_fast_dequeue()) This patch adds atomic_qlen (in the same location than qlen) and renames the following helpers, since we want to express they can be used without qdisc lock, and that qlen is no longer percpu. - qdisc_qstats_cpu_qlen_dec -> qdisc_qstats_atomic_qlen_dec() - qdisc_qstats_cpu_qlen_inc -> qdisc_qstats_atomic_qlen_inc() Later (net-next) we might revert this patch by tracking all these qlen uses and replace them by a more efficient method (not having to access a precise qlen, but an empty/non_empty status that might be less expensive to maintain/track). Another possibility is to have a legacy pfifo_fast version that would be used when used a a child qdisc, since the parent qdisc needs a spinlock anyway. But then, future lockless qdiscs would also have the same problem. Fixes: 7e66016f2c65 ("net: sched: helpers to sum qlen and qlen for per cpu logic") Signed-off-by: Eric Dumazet Cc: John Fastabend Cc: Jamal Hadi Salim Cc: Cong Wang Cc: Jiri Pirko Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

Documentation: bring operstate documentation up-to-date

2019-02-11T20:38:51Z

Netlink has moved from bitmasks to group numbers long ago. Signed-off-by: Jouke Witteveen Signed-off-by: David S. Miller

net/sched: Replace call_rcu_bh() and rcu_barrier_bh()

2018-12-01T20:38:46Z

Now that call_rcu()'s callback is not invoked until after bh-disable regions of code have completed (in addition to explicitly marked RCU read-side critical sections), call_rcu() can be used in place of call_rcu_bh(). Similarly, rcu_barrier() can be used in place o frcu_barrier_bh(). This commit therefore makes these changes. Signed-off-by: Paul E. McKenney Cc: Jamal Hadi Salim Cc: Cong Wang Cc: Jiri Pirko Cc: "David S. Miller" Cc:

net: sched: avoid writing on noop_qdisc

2018-10-11T05:49:16Z

While noop_qdisc.gso_skb and noop_qdisc.skb_bad_txq are not used in other places, it seems not correct to overwrite their fields in dev_init_scheduler_queue(). noop_qdisc is essentially a shared and read-only object, even if it is not marked as const because of some implementation detail. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

net: sched: make function qdisc_free_cb() static

2018-09-28T18:04:58Z

Fixes the following sparse warning: net/sched/sch_generic.c:944:6: warning: symbol 'qdisc_free_cb' was not declared. Should it be static? Fixes: 3a7d0d07a386 ("net: sched: extend Qdisc with rcu") Signed-off-by: Wei Yongjun Signed-off-by: David S. Miller

net: sched: extend Qdisc with rcu

2018-09-26T03:17:35Z

Currently, Qdisc API functions assume that users have rtnl lock taken. To implement rtnl unlocked classifiers update interface, Qdisc API must be extended with functions that do not require rtnl lock. Extend Qdisc structure with rcu. Implement special version of put function qdisc_put_unlocked() that is called without rtnl lock taken. This function only takes rtnl lock if Qdisc reference counter reached zero and is intended to be used as optimization. Signed-off-by: Vlad Buslov Acked-by: Jiri Pirko Signed-off-by: David S. Miller

net: sched: rename qdisc_destroy() to qdisc_put()

2018-09-26T03:17:35Z

Current implementation of qdisc_destroy() decrements Qdisc reference counter and only actually destroy Qdisc if reference counter value reached zero. Rename qdisc_destroy() to qdisc_put() in order for it to better describe the way in which this function currently implemented and used. Extract code that deallocates Qdisc into new private qdisc_destroy() function. It is intended to be shared between regular qdisc_put() and its unlocked version that is introduced in next patch in this series. Signed-off-by: Vlad Buslov Acked-by: Jiri Pirko Signed-off-by: David S. Miller

net: Add and use skb_mark_not_on_list().

2018-09-10T17:06:54Z

An SKB is not on a list if skb->next is NULL. Codify this convention into a helper function and use it where we are dequeueing an SKB and need to mark it as such. Signed-off-by: David S. Miller

net: remove bypassed check in sch_direct_xmit()

2018-05-31T17:26:19Z

Checking netif_xmit_frozen_or_stopped() at the end of sch_direct_xmit() is being bypassed. This is because "ret" from sch_direct_xmit() will be either NETDEV_TX_OK or NETDEV_TX_BUSY, and only ret == NETDEV_TX_OK == 0 will reach the condition: if (ret && netif_xmit_frozen_or_stopped(txq)) return false; This patch cleans up the code by removing the whole condition. For more discussion about this, please refer to https://marc.info/?t=152727195700008 Signed-off-by: Song Liu Cc: John Fastabend Cc: Alexei Starovoitov Cc: David S. Miller Signed-off-by: David S. Miller

pfifo_fast: drop unneeded additional lock on dequeue

2018-05-17T16:46:54Z

After the previous patch, for NOLOCK qdiscs, q->seqlock is always held when the dequeue() is invoked, we can drop any additional locking to protect such operation. Signed-off-by: Paolo Abeni Signed-off-by: David S. Miller