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.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: linuxppc-dev@lists.ozlabs.org
---
Compile-tested only
---
arch/powerpc/platforms/powermac/pic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/powermac/pic.c b/arch/powerpc/platforms/powermac/pic.c
index 4c24bf60d39d2834..90ada1209c118902 100644
--- a/arch/powerpc/platforms/powermac/pic.c
+++ b/arch/powerpc/platforms/powermac/pic.c
@@ -321,7 +321,7 @@ static void __init pmac_pic_probe_oldstyle(void)
max_irqs = max_real_irqs = 64;
/* We might have a second cascaded heathrow */
- slave = of_find_node_by_name(master, "mac-io");
+ slave = of_get_child_by_name(master, "mac-io");
/* Check ordering of master & slave */
if (of_device_is_compatible(master, "gatwick")) {--
1.9.1
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.
So this is a logic change AFAICS, and I have no idea what machines we'd need to
test on to check it.
So I think an of_node_get(master) would be safer and also fix the refcounting.
cheers
Hi Michael,
On Fri, Jan 30, 2015 at 5:09 AM, Michael Ellerman [off-list ref] wrote:
On Wed, 2015-14-01 at 13:51:57 UTC, Geert Uytterhoeven wrote:
quoted
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.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
On Fri, 2015-01-30 at 10:00 +0100, Geert Uytterhoeven wrote:
Hi Michael,
On Fri, Jan 30, 2015 at 5:09 AM, Michael Ellerman [off-list ref] wrote:
quoted
On Wed, 2015-14-01 at 13:51:57 UTC, Geert Uytterhoeven wrote:
quoted
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.
Yeah OK, I don't have a system or an example device tree to check.
quoted
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.
Yep. Ben or Paul might know, but even then their memory may not be perfect :)
quoted
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.
I think so. Given how few of these machines are around it's easy to break them
with an inadvertent change like this, so I think it's better to be safe.
Wanna send a patch for that?
cheers