Message ID | 1421243519-6257-2-git-send-email-geert+renesas@glider.be (mailing list archive) |
---|---|
State | Changes Requested |
Delegated to: | Michael Ellerman |
Headers | show |
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 <mpe@ellerman.id.au> 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. 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 <mpe@ellerman.id.au> 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. Yeah OK, I don't have a system or an example device tree to check. > > 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 :) > > 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
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")) {
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(-)