On Thu, Sep 14, 2023 at 01:01:26PM +0100, Jonathan Cameron wrote: > On Wed, 13 Sep 2023 16:37:59 +0000 > James Morse <james.morse@xxxxxxx> wrote: > > > register_cpu_capacity_sysctl() adds a property to sysfs that describes > > the CPUs capacity. This is done from a subsys_initcall() that assumes > > all possible CPUs are registered. > > > > With CPU hotplug, possible CPUs aren't registered until they become > > present, (or for arm64 enabled). This leads to messages during boot: > > | register_cpu_capacity_sysctl: too early to get CPU1 device! > > and once these CPUs are added to the system, the file is missing. > > > > Move this to a cpuhp callback, so that the file is created once > > CPUs are brought online. This covers CPUs that are added late by > > mechanisms like hotplug. > > One observable difference is the file is now missing for offline CPUs. > > > > Signed-off-by: James Morse <james.morse@xxxxxxx> > > --- > > If the offline CPUs thing is a problem for the tools that consume > > this value, we'd need to move cpu_capacity to be part of cpu.c's > > common_cpu_attr_groups. > > I think we should do that anyway and then use an is_visible() if we want to > change whether it is visible in offline cpus. > > Dynamic sysfs file creation is horrible - particularly when done > from an totally different file from where the rest of the attributes > are registered. I'm curious what the history behind that is. > > Whilst here, why is there a common_cpu_attr_groups which is > identical to the hotpluggable_cpu_attr_groups in base/cpu.c? > > > +CC GregKH > Given changes in drivers/base/ It would be good to have a comment on this from Greg before I post an updated series of James' patches with most of the comments addressed, possibly later today. Thanks. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
