From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: [1/3] powerpc/pmac: Fix DT refcount imbalance in pmac_pic_probe_oldstyle Date: Fri, 30 Jan 2015 10:00:23 +0100 Message-ID: References: <1421243519-6257-2-git-send-email-geert+renesas@glider.be> <20150130040904.8F89D1402A7@ozlabs.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <20150130040904.8F89D1402A7-mnsaURCQ41sdnm+yROfE0A@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Michael Ellerman Cc: Geert Uytterhoeven , Benjamin Herrenschmidt , Bryan Wu , Richard Purdie , Jingoo Han , Lee Jones , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: devicetree@vger.kernel.org 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. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html