On 06/08/17 02:05, Mark Rutland wrote: > 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. Thanks Mark! The "#ifdef CONFIG_GENERIC_CPU_DEVICES" in cpu_dev_register_generic() explains why we don't see the error on ARM, ARM64, etc. Without the CONFIG option, register_cpu(cpu, i) is not called. > 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> Agree with Mark's request to update the commit message, and also I would like to see this shaken out in the -next tree. Acked-by: Frank Rowand <frowand.list@xxxxxxxxx> > > Thanks, > Mark. >
