From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
Hangbin Liu <liuhangbin@gmail.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Magnus Karlsson <magnus.karlsson@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH RFC bpf-next 0/4] Clean up and document RCU-based object protection for XDP_REDIRECT
Date: Fri, 23 Apr 2021 13:05:15 +0200 [thread overview]
Message-ID: <161917591559.102337.3558507780042453425.stgit@toke.dk> (raw)
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. I'm sending this as RFC since I don't have any i40e hardware to
test on. A complete submission would also involve going through all the drivers,
of course, but I wanted to get some feedback onthis first. I did test on mlx5,
but that uses an rhashtable in the driver code, so we can't actually remove the
top-level rcu_read_lock() from that without getting lockdep splats.
Patches 1-2 are prepatory: Patch 1 adds Paul's unrcu_pointer() helper 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 patch 4 is an example of driver changes,
removing the rcu_read_lock() from i40e.
Please take a look, and let me know if you think this is the right direction for
clarifying the usage.
Thanks,
-Toke
[0] https://lore.kernel.org/bpf/20210415173551.7ma4slcbqeyiba2r@kafai-mbp.dhcp.thefacebook.com/
---
Paul E. McKenney (1):
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
Toke Høiland-Jørgensen (3):
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
i40e: remove rcu_read_lock() around XDP program invocation
drivers/net/ethernet/intel/i40e/i40e_txrx.c | 2 -
drivers/net/ethernet/intel/i40e/i40e_xsk.c | 6 +--
include/net/xdp_sock.h | 2 +-
kernel/bpf/cpumap.c | 14 ++++--
kernel/bpf/devmap.c | 52 +++++++++------------
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 +++++++-----
10 files changed, 85 insertions(+), 58 deletions(-)
next reply other threads:[~2021-04-23 11:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-23 11:05 Toke Høiland-Jørgensen [this message]
2021-04-23 11:05 ` [PATCH RFC bpf-next 1/4] rcu: Create an unrcu_pointer() to remove __rcu from a pointer Toke Høiland-Jørgensen
2021-04-23 11:05 ` [PATCH RFC bpf-next 2/4] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref Toke Høiland-Jørgensen
2021-04-23 11:05 ` [PATCH RFC bpf-next 3/4] xdp: add proper __rcu annotations to redirect map entries Toke Høiland-Jørgensen
2021-04-23 11:05 ` [PATCH RFC bpf-next 4/4] i40e: remove rcu_read_lock() around XDP program invocation Toke Høiland-Jørgensen
2021-04-23 13:57 ` Maciej Fijalkowski
2021-04-23 20:33 ` Toke Høiland-Jørgensen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=161917591559.102337.3558507780042453425.stgit@toke.dk \
--to=toke@redhat.com \
--cc=bpf@vger.kernel.org \
--cc=hawk@kernel.org \
--cc=kafai@fb.com \
--cc=liuhangbin@gmail.com \
--cc=magnus.karlsson@gmail.com \
--cc=netdev@vger.kernel.org \
--cc=paulmck@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).