linux-kernel - Re: [PATCH v5 1/3] of: cache phandle nodes to reduce cost of of_find_node_by

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Message-ID: <CANk1AXSvVD5x7TKQV_HZm=9Lzeymm5H3p7DZPiAc-RRRxdAOZg@mail.gmail.com>
Date:   Wed, 13 Jun 2018 09:42:50 -0500
From:   Alan Tull <atull@...nel.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, cpandya@...eaurora.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fpga@...r.kernel.org, Moritz Fischer <mdf@...nel.org>
Subject: Re: [PATCH v5 1/3] of: cache phandle nodes to reduce cost of of_find_node_by_phandle()

On Tue, Jun 12, 2018 at 1:16 PM, Alan Tull <atull@...nel.org> wrote:
> On Sun, Mar 4, 2018 at 6:14 PM,  <frowand.list@...il.com> wrote:
>
> Hi Frank,
>
> I'm investigating a refcount use-after-free warning that happens after
> overlays are applied, removed, reapplied a few (typically three) times
> (see below).  This is new in v4.17, didn't happen in v4.16.  As I was
> investigating I found that rebuilding the phandle_cache after overlays
> are applied or removed seems to help.

I was probably wrong about this.  The more I look at the phandle_cache code,
the more it looks looks good and straightforward.  Probably disabling
phandle_cache is 'fixing' things through some weird side effect.  I'll
keep investigating.  Sorry for the noise.

Alan