linux-kernel - Re: [PATCH v2 2/2] of: overlay: Fix cleanup order in of_overlay

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Message-ID: <CAMuHMdVFR3FPVAM2J_L2HvNUzkJsQM57SJJ2CMux71M4dhZYfQ@mail.gmail.com>
Date:   Mon, 4 Dec 2017 20:45:10 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Frank Rowand <frowand.list@...il.com>,
        Colin King <colin.king@...onical.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] of: overlay: Fix cleanup order in of_overlay_apply()

Hi Rob,

On Mon, Dec 4, 2017 at 8:35 PM, Rob Herring <robh+dt@...nel.org> wrote:
> On Mon, Dec 4, 2017 at 9:47 AM, Geert Uytterhoeven
> <geert+renesas@...der.be> wrote:
>> The special overlay mutex is taken first, hence it should be released
>> last in the error path.
>>
>> Move "mutex_lock(&of_mutex)" up, as suggested by Frank, as
>> free_overlay_changeset() should be called with that mutex held if any
>> non-trivial cleanup is to be done.
>
> Not holding the of_mutex for of_resolve_phandles is just wrong.
> Without it, a node and new phandle could be added via of_attach_node
> making the max phandle wrong.

After my patch it's held, so what's the problem?

> Now, with the 2 mutexes adjacent, what is the point of even having the
> of_overlay_mutex? Seems like we should just drop it.

Frank?

> I also don't think we really need to hold the mutex during post-apply
> notifiers. It also seems like some steps could be moved outside the
> mutex(es) like init_overlay_changeset().

Perhaps.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds