LKML Archive on
help / color / mirror / Atom feed
From: Geert Uytterhoeven <>
To: Michael Ellerman <>
Cc: Geert Uytterhoeven <>,
	Benjamin Herrenschmidt <>,
	Bryan Wu <>, Richard Purdie <>,
	Jingoo Han <>,
	Lee Jones <>,
	"" <>,
	"" <>,
	"" <>
Subject: Re: [1/3] powerpc/pmac: Fix DT refcount imbalance in pmac_pic_probe_oldstyle
Date: Fri, 30 Jan 2015 10:00:23 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Michael,

On Fri, Jan 30, 2015 at 5:09 AM, Michael Ellerman <> wrote:
> On Wed, 2015-14-01 at 13:51:57 UTC, Geert Uytterhoeven wrote:
>> of_find_node_by_name() calls of_node_put() on its "from" parameter,
>> which must not be done on "master", as it's still in use, and will be
>> released manually later.  This may cause a zero kref refcount.
>> Use of_get_child_by_name() instead to fix this.
> But of_find_node_by_name() searches *all* nodes, not just the children of the
> parameter.

That's correct. However, I guess the second mac-io will just be a direct child.

> So this is a logic change AFAICS, and I have no idea what machines we'd need to
> test on to check it.

Originally it comes from arch/ppc/platforms/pmac_pic.c, added in 2002 in
full-history-linux commit 5ea3254844ae344a
("Import arch/ppc and include/asm-ppc changes from linuxppc_2_5 tree").

I've also checked my linuxppc mail archives from 1997-2002, but couldn't find
the actual patch and a description.

So I don't know on which machines it's needed.

> So I think an of_node_get(master) would be safer and also fix the refcounting.

If no one can confirm the above, that may indeed be the best solution.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

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

  reply	other threads:[~2015-01-30  9:00 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-14 13:51 [PATCH 0/3] Use of_get_child_by_name() instead of of_find_node_by_name() Geert Uytterhoeven
2015-01-14 13:51 ` [PATCH 1/3] powerpc/pmac: Fix DT refcount imbalance in pmac_pic_probe_oldstyle Geert Uytterhoeven
2015-01-30  4:09   ` [1/3] " Michael Ellerman
2015-01-30  9:00     ` Geert Uytterhoeven [this message]
2015-02-03  1:12       ` Michael Ellerman
2015-01-14 13:51 ` [PATCH 2/3] leds: leds-mc13783: Use of_get_child_by_name() instead of refcount hack Geert Uytterhoeven
2015-01-14 18:42   ` Bryan Wu
2015-01-14 13:51 ` [PATCH 3/3] backlight: 88pm860x_bl: " Geert Uytterhoeven
2015-01-18 12:46   ` Lee Jones

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='' \ \ \ \ \ \ \ \ \ \ \ \
    --subject='Re: [1/3] powerpc/pmac: Fix DT refcount imbalance in pmac_pic_probe_oldstyle' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).