On Wed, Jun 07, 2017 at 08:49:43PM -0700, Frank Rowand wrote: > On 06/07/17 11:39, Wesley Terpstra wrote: > > It was a while ago that I debugged this. I already reported this bug > > to Benjamin Herrenschmidt (now in CC), and I believe he has a patch of > > his own to fix the same issue. > > > > As I understand it, of_core_init sets up the OF entries in > > /sys/firmware/devicetree. During platform bringup, when the system > > describes the cpu + cache hierarchy, it also makes an of_node symlink > > into that directory. However, if it doesn't exist yet, you get the > > warning. > > > > # ls -l /sys/devices/system/cpu/cpu3/of_node > > lrwxrwxrwx 1 root root 0 Jan 1 00:00 > > /sys/devices/system/cpu/cpu3/of_node -> > > ../../../../firmware/devicetree/base/cpus/cpu@3 > > > > On Wed, Jun 7, 2017 at 2:35 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > >> On Wed, Jun 07, 2017 at 09:07:20AM +0200, Geert Uytterhoeven wrote: > >>> CC devicetree folks > >>> > >>> On Wed, Jun 7, 2017 at 12:59 AM, Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote: > >>>> From: "Wesley W. Terpstra" <wesley@xxxxxxxxxx> > >>>> > >>>> This fixes: [ 0.010000] cpu cpu0: Error -2 creating of_node link > >>>> ... which you get for every CPU on all architectures with a OF cpu/ node. > >> > >> I take it this means a /cpus node? Or the /cpus/cpu@* nodes? > >> > >> I'm not seeing this on arm64 when booting v4.12-rc4 with DT, so clearly > >> this doesn't affect all such architectures. > >> > >> What path are these errors happening in? > > On the surface, the patch looks reasonable. But it is not obvious to me why > the error message is occurring. I would like to understand the cause before > saying the patch is good. > > What kernel version is showing the error? For a specific architecture > (the patch lists 'riscv, nios, etc'), which config and device tree source? > > And again, what is the calling path? >From having grepped around, I think this affects architectures which select CONFIG_GENERIC_CPU_DEVICES, which includes nios2. In that case, driver_init() calls cpu_dev_init() before calling of_core_init(). Then we get the callchain: cpu_dev_init() -> cpu_dev_register_generic() -> register_cpu(cpu, i) -> device_register(&cpu->dev) -> device_add(dev) -> device_add_class_symlinks(dev) ... in device_add_class_symlinks, we we dev->of_node, and call sysfs_create_link(), which fails because we haven't called of_core_init() to register the sysfs devicetree directory yet. Given that, this patch makes sense to me. FWIW, with the commit message updated to describe the particular ordering problem: Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Thanks, Mark. -- 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
