On 6/9/21 3:33 AM, Toke Høiland-Jørgensen wrote:

During the discussion[0] of Hangbin's multicast patch series, Martin pointed out
that the lifetime of the RCU-protected  map entries used by XDP_REDIRECT is by
no means obvious. I promised to look into cleaning this up, and Paul helpfully
provided some hints and a new unrcu_pointer() helper to aid in this.

This is mostly a documentation exercise, clearing up the description of the
lifetime expectations and adding __rcu annotations so sparse and lockdep can
help verify it.

Patches 1-2 are prepatory: Patch 1 adds Paul's unrcu_pointer() helper (which has
already been added to his tree) and patch 2 is a small fix for
dev_get_by_index_rcu() so lockdep understands _bh-disabled access to it. Patch 3
is the main bit that adds the __rcu annotations and updates documentation
comments, and the rest are patches updating the drivers, with one patch per
distinct maintainer.

Unfortunately I don't have any hardware to test any of the driver patches;
Jesper helpfully verified that it doesn't break anything on i40e, but the rest
of the driver patches are only compile-tested.

[0] https://lore.kernel.org/bpf/20210415173551.7ma4slcbqeyiba2r@kafai-mbp.dhcp.thefacebook.com/ (local)

Paul E. McKenney (1):
   rcu: Create an unrcu_pointer() to remove __rcu from a pointer

Toke Høiland-Jørgensen (16):
   bpf: allow RCU-protected lookups to happen from bh context
   dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU
     dev ref
   xdp: add proper __rcu annotations to redirect map entries
   ena: remove rcu_read_lock() around XDP program invocation
   bnxt: remove rcu_read_lock() around XDP program invocation
   thunderx: remove rcu_read_lock() around XDP program invocation
   freescale: remove rcu_read_lock() around XDP program invocation
   net: intel: remove rcu_read_lock() around XDP program invocation
   marvell: remove rcu_read_lock() around XDP program invocation
   mlx4: remove rcu_read_lock() around XDP program invocation
   nfp: remove rcu_read_lock() around XDP program invocation
   qede: remove rcu_read_lock() around XDP program invocation
   sfc: remove rcu_read_lock() around XDP program invocation
   netsec: remove rcu_read_lock() around XDP program invocation
   stmmac: remove rcu_read_lock() around XDP program invocation
   net: ti: remove rcu_read_lock() around XDP program invocation

  drivers/net/ethernet/amazon/ena/ena_netdev.c  |  3 --
  drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c |  2 -
  .../net/ethernet/cavium/thunder/nicvf_main.c  |  2 -
  .../net/ethernet/freescale/dpaa/dpaa_eth.c    |  8 +--
  .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  |  3 --
  drivers/net/ethernet/intel/i40e/i40e_txrx.c   |  2 -
  drivers/net/ethernet/intel/i40e/i40e_xsk.c    |  6 +--
  drivers/net/ethernet/intel/ice/ice_txrx.c     |  6 +--
  drivers/net/ethernet/intel/ice/ice_xsk.c      |  6 +--
  drivers/net/ethernet/intel/igb/igb_main.c     |  2 -
  drivers/net/ethernet/intel/igc/igc_main.c     |  7 +--
  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |  2 -
  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c  |  6 +--
  .../net/ethernet/intel/ixgbevf/ixgbevf_main.c |  2 -
  drivers/net/ethernet/marvell/mvneta.c         |  2 -
  .../net/ethernet/marvell/mvpp2/mvpp2_main.c   |  4 --
  drivers/net/ethernet/mellanox/mlx4/en_rx.c    |  8 +--
  .../ethernet/netronome/nfp/nfp_net_common.c   |  2 -
  drivers/net/ethernet/qlogic/qede/qede_fp.c    |  6 ---
  drivers/net/ethernet/sfc/rx.c                 |  9 +---
  drivers/net/ethernet/socionext/netsec.c       |  3 --
  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 10 +---
  drivers/net/ethernet/ti/cpsw_priv.c           | 10 +---
  include/linux/rcupdate.h                      | 14 +++++
  include/net/xdp_sock.h                        |  2 +-
  kernel/bpf/cpumap.c                           | 14 +++--
  kernel/bpf/devmap.c                           | 52 ++++++++-----------
  kernel/bpf/hashtab.c                          | 21 +++++---
  kernel/bpf/helpers.c                          |  6 +--
  kernel/bpf/lpm_trie.c                         |  6 ++-
  net/core/dev.c                                |  2 +-
  net/core/filter.c                             | 28 ++++++++++
  net/xdp/xsk.c                                 |  4 +-
  net/xdp/xsk.h                                 |  4 +-
  net/xdp/xskmap.c                              | 29 ++++++-----
  35 files changed, 134 insertions(+), 159 deletions(-)

Martin, could you help review this patch set? You had participated
in early discussions related to this patch. Thanks!