netdev - [PATCH bpf-next 0/4] xsk: various CPU barrier and {READ, WRITE}

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Date:   Thu, 22 Aug 2019 11:13:02 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...il.com>,
        magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        bpf@...r.kernel.org, bjorn.topel@...el.com,
        jonathan.lemon@...il.com,
        syzbot+c82697e3043781e08802@...kaller.appspotmail.com,
        hdanton@...a.com, i.maximets@...sung.com
Subject: [PATCH bpf-next 0/4] xsk: various CPU barrier and {READ, WRITE}_ONCE fixes

This is a four patch series of various barrier, {READ, WRITE}_ONCE
cleanups in the AF_XDP socket code. More details can be found in the
corresponding commit message.

For an AF_XDP socket, most control plane operations are done under the
control mutex (struct xdp_sock, mutex), but there are some places
where members of the struct is read outside the control mutex. This,
as pointed out by Daniel in [1], requires proper {READ,
WRITE}_ONCE-correctness [2] [3]. To address this, and to simplify the
code, the state variable (introduced by Ilya), is now used a point of
synchronization ("is the socket in a valid state, or not").

Thanks,
Björn

[1] https://lore.kernel.org/bpf/beef16bb-a09b-40f1-7dd0-c323b4b89b17@iogearbox.net/
[2] https://lwn.net/Articles/793253/
[3] https://github.com/google/ktsan/wiki/READ_ONCE-and-WRITE_ONCE

Björn Töpel (4):
  xsk: avoid store-tearing when assigning queues
  xsk: add proper barriers and {READ, WRITE}_ONCE-correctness for state
  xsk: avoid store-tearing when assigning umem
  xsk: lock the control mutex in sock_diag interface

 net/xdp/xsk.c      | 61 ++++++++++++++++++++++++++++++++--------------
 net/xdp/xsk_diag.c |  3 +++
 2 files changed, 46 insertions(+), 18 deletions(-)

-- 
2.20.1