netdev - Re: [net PATCH 0/3] Fix two teardown bugs for BPF maps cpumap and devmap

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Message-ID: <3d250a8a-a707-9dc3-a224-14a285646427@iogearbox.net>
Date:   Thu, 9 Aug 2018 21:54:01 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org
Cc:     Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        jhsiao@...hat.com
Subject: Re: [net PATCH 0/3] Fix two teardown bugs for BPF maps cpumap and
 devmap

On 08/08/2018 11:00 PM, Jesper Dangaard Brouer wrote:
> Removing entries from cpumap and devmap, goes through a number of
> syncronization steps to make sure no new xdp_frames can be enqueued.
> But there is a small chance, that xdp_frames remains which have not
> been flushed/processed yet.  Flushing these during teardown, happens
> from RCU context and not as usual under RX NAPI context.
> 
> The optimization introduced in commt 389ab7f01af9 ("xdp: introduce
> xdp_return_frame_rx_napi"), missed that the flush operation can also
> be called from RCU context.  Thus, we cannot always use the
> xdp_return_frame_rx_napi call, which take advantage of the protection
> provided by XDP RX running under NAPI protection.
> 
> The samples/bpf xdp_redirect_cpu have a --stress-mode, that is
> adjusted to easier reproduce (verified by Red Hat QA).

Applied to bpf, thanks Jesper!