From: John Fastabend <john.fastabend@gmail.com>
To: bjorn.topel@gmail.com, bpf@vger.kernel.org, toke@redhat.com,
toshiaki.makita1@gmail.com
Cc: netdev@vger.kernel.org, john.fastabend@gmail.com, ast@kernel.org,
daniel@iogearbox.net
Subject: [bpf-next PATCH v2 0/2] xdp devmap improvements cleanup
Date: Sat, 11 Jan 2020 18:36:59 -0800 [thread overview]
Message-ID: <157879606461.8200.2816751890292483534.stgit@john-Precision-5820-Tower> (raw)
Couple cleanup patches to recently posted series[0] from Bjorn to
cleanup and optimize the devmap usage. Patches have commit ids
the cleanup applies to.
Toshiaki, noted that virtio_net depends on rcu_lock being held
when calling xdp flush routines. This is specific to virtio_net
dereferencing xdp program to determine if xdp is enabled or not.
More typical pattern is to look at a flag set by the driver, at
least in the case of real hardware drivers. veth has a similar
requirement where it derferences the peer netdev priv structure
requiring the rcu_read_lock. I believe its better to put the
rcu_read_lock()/unlock() pair where its actually used in the
driver. FWIW in other xdp paths we expect driver writers to
place rcu_read_lock/unlock pairs where they are needed as well
so this keeps that expectation. Also it improves readability
making it obvious why the rcu_read_lock and unlock pair is
needed. In the virtio case we can probably do some further
cleanup and remove it altogether if we want. For more details
see patch 2/2.
[0] https://www.spinics.net/lists/netdev/msg620639.html
v2: Place rcu_read_{un}lock pair in virtio_net and veth drivers
so we don't break this requirement when removing rcu read
lock from devmap.
---
John Fastabend (2):
bpf: xdp, update devmap comments to reflect napi/rcu usage
bpf: xdp, remove no longer required rcu_read_{un}lock()
drivers/net/veth.c | 6 +++++-
drivers/net/virtio_net.c | 8 ++++++--
kernel/bpf/devmap.c | 26 ++++++++++++++------------
3 files changed, 25 insertions(+), 15 deletions(-)
--
Signature
next reply other threads:[~2020-01-12 2:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-12 2:36 John Fastabend [this message]
2020-01-12 2:37 ` [bpf-next PATCH v2 1/2] bpf: xdp, update devmap comments to reflect napi/rcu usage John Fastabend
2020-01-12 7:47 ` Maciej Fijalkowski
2020-01-14 3:27 ` John Fastabend
2020-01-12 11:21 ` Toke Høiland-Jørgensen
2020-01-12 2:37 ` [bpf-next PATCH v2 2/2] bpf: xdp, remove no longer required rcu_read_{un}lock() John Fastabend
2020-01-12 6:49 ` Maciej Fijalkowski
2020-01-14 3:25 ` John Fastabend
2020-01-14 0:31 ` Maciej Fijalkowski
2020-01-12 11:22 ` 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=157879606461.8200.2816751890292483534.stgit@john-Precision-5820-Tower \
--to=john.fastabend@gmail.com \
--cc=ast@kernel.org \
--cc=bjorn.topel@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=netdev@vger.kernel.org \
--cc=toke@redhat.com \
--cc=toshiaki.makita1@gmail.com \
/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).