On Wed, Apr 16, 2014 at 4:33 PM, Rob Herring <robherring2@xxxxxxxxx> wrote: > On Wed, Apr 16, 2014 at 4:23 PM, delicious quinoa > <delicious.quinoa@xxxxxxxxx> wrote: >> On Thu, Apr 3, 2014 at 3:40 PM, delicious quinoa >> <delicious.quinoa@xxxxxxxxx> wrote: >>> On Fri, Mar 28, 2014 at 1:27 PM, delicious quinoa >>> <delicious.quinoa@xxxxxxxxx> wrote: >>>> On Tue, Mar 18, 2014 at 4:55 PM, Pantelis Antoniou >>>> <pantelis.antoniou@xxxxxxxxxxxx> wrote: >>>>> The following patchset introduces Device Tree overlays, a method >>>>> of dynamically altering the kernel's live Device Tree, along with >>>>> a generic interface to use it in a board agnostic manner. > > [snip] > >>>> I can get a NULL pointer when I apply and remove an overlay and the >>>> conditions are right. The overlay applies correctly. The crash is >>>> when I do the rmdir. My overlay is: >>>> >>>> /dts-v1/; >>>> /plugin/; >>>> / { >>>> fragment@0 { >>>> target-path="/soc"; >>>> __overlay__ { >>>> #address-cells = <1>; >>>> #size-cells = <1>; >>>> agpio0: agpio0 { >>>> compatible = "altr,pio-1.0"; >>>> reg = <0xff210040 0x10>; >>> >>> Added some printks and got a bit further with debug. If I leave this >>> as-is, the platform device has 2 resources. We get the NULL pointer in >>> __release_resource() when releasing the first one (reg). If I remove >>> this one line ('reg =') the crash goes away. So in this case, we are >>> ok when releasing an irq resource but get a NULL pointer when removing >>> a reg resource. Don't know why at this point. >> >> The crash is confirmed on v4 patches as well. The immediate cause of the crash: >> >> static int __release_resource(struct resource *old) >> { >> struct resource *tmp, **p; >> >> p = &old->parent->child; >> for (;;) { >> tmp = *p; <===kablooey >> ... >> >> when __release_resource() is called for the reg resource, it does 'p = >> &olde->parent->child' and then crashes when it does 'tmp = *p'. >> >> Root cause: It appears that there isn't any code in drivers/of/ that >> eventually calls __request_resource() or __insert_resource() so the >> resource's parents/sibling pointers are never initialized. Maybe I'm >> missing some patches or something. > > It's probably related to this issue: > > https://groups.google.com/forum/#!topic/fa.linux.kernel/CTx1ReiOjnQ > http://www.mail-archive.com/linuxppc-dev@xxxxxxxxxxxxxxxx/msg63678.html > > Rob Yes, that's the same root problem (devices are released by 'of' code that were never added using resource.c code). Adding a "of_device_unpopulate()" function to a bunch of drivers won't work because the crash happens without loading any driver. Alan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html