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* [PATCH net-next v3 0/2] net: sched: Do not drop root lock in tcf_qevent_handle()
@ 2020-07-14 17:03 Petr Machata
  2020-07-14 17:03 ` [PATCH net-next v3 1/2] " Petr Machata
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Petr Machata @ 2020-07-14 17:03 UTC (permalink / raw)
  To: netdev
  Cc: David Miller, Jakub Kicinski, Cong Wang, Ido Schimmel, Jiri Pirko,
	Eric Dumazet, Petr Machata

Mirred currently does not mix well with blocks executed after the qdisc
root lock is taken. This includes classification blocks (such as in PRIO,
ETS, DRR qdiscs) and qevents. The locking caused by the packet mirrored by
mirred can cause deadlocks: either when the thread of execution attempts to
take the lock a second time, or when two threads end up waiting on each
other's locks.

The qevent patchset attempted to not introduce further badness of this
sort, and dropped the lock before executing the qevent block. However this
lead to too little locking and races between qdisc configuration and packet
enqueue in the RED qdisc.

Before the deadlock issues are solved in a way that can be applied across
many qdiscs reasonably easily, do for qevents what is done for the
classification blocks and just keep holding the root lock.

That is done in patch #1. Patch #2 then drops the now unnecessary root_lock
argument from Qdisc_ops.enqueue.

v3:
- Patch #2:
    - Add a S-o-b.

v2:
- Patch #2:
    - Turn this into a proper revert. No actual changes.

Petr Machata (2):
  net: sched: Do not drop root lock in tcf_qevent_handle()
  Revert "net: sched: Pass root lock to Qdisc_ops.enqueue"

 include/net/pkt_cls.h     |  4 ++--
 include/net/sch_generic.h |  6 ++----
 net/core/dev.c            |  4 ++--
 net/sched/cls_api.c       |  8 +-------
 net/sched/sch_atm.c       |  4 ++--
 net/sched/sch_blackhole.c |  2 +-
 net/sched/sch_cake.c      |  2 +-
 net/sched/sch_cbq.c       |  4 ++--
 net/sched/sch_cbs.c       | 18 +++++++++---------
 net/sched/sch_choke.c     |  2 +-
 net/sched/sch_codel.c     |  2 +-
 net/sched/sch_drr.c       |  4 ++--
 net/sched/sch_dsmark.c    |  4 ++--
 net/sched/sch_etf.c       |  2 +-
 net/sched/sch_ets.c       |  4 ++--
 net/sched/sch_fifo.c      |  6 +++---
 net/sched/sch_fq.c        |  2 +-
 net/sched/sch_fq_codel.c  |  2 +-
 net/sched/sch_fq_pie.c    |  2 +-
 net/sched/sch_generic.c   |  4 ++--
 net/sched/sch_gred.c      |  2 +-
 net/sched/sch_hfsc.c      |  6 +++---
 net/sched/sch_hhf.c       |  2 +-
 net/sched/sch_htb.c       |  4 ++--
 net/sched/sch_multiq.c    |  4 ++--
 net/sched/sch_netem.c     |  8 ++++----
 net/sched/sch_pie.c       |  2 +-
 net/sched/sch_plug.c      |  2 +-
 net/sched/sch_prio.c      |  6 +++---
 net/sched/sch_qfq.c       |  4 ++--
 net/sched/sch_red.c       | 10 +++++-----
 net/sched/sch_sfb.c       |  4 ++--
 net/sched/sch_sfq.c       |  2 +-
 net/sched/sch_skbprio.c   |  2 +-
 net/sched/sch_taprio.c    |  4 ++--
 net/sched/sch_tbf.c       | 10 +++++-----
 net/sched/sch_teql.c      |  4 ++--
 37 files changed, 77 insertions(+), 85 deletions(-)

-- 
2.20.1


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-07-17  0:37 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2020-07-14 17:03 [PATCH net-next v3 0/2] net: sched: Do not drop root lock in tcf_qevent_handle() Petr Machata
2020-07-14 17:03 ` [PATCH net-next v3 1/2] " Petr Machata
2020-07-14 17:03 ` [PATCH net-next v3 2/2] Revert "net: sched: Pass root lock to Qdisc_ops.enqueue" Petr Machata
2020-07-17  0:37 ` [PATCH net-next v3 0/2] net: sched: Do not drop root lock in tcf_qevent_handle() Jakub Kicinski

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