On Mon, Nov 15, 2021 at 11:11:44PM +0000, Alexey Makhalov wrote: > > > > On Nov 15, 2021, at 4:58 AM, Michal Hocko <mhocko@xxxxxxxx> wrote: > > > > On Mon 15-11-21 11:04:16, Alexey Makhalov wrote: > >> Hi Michal, > >> > >>> > >>> I have asked several times for details about the specific setup that has > >>> led to the reported crash. Without much success so far. Reproduction > >>> steps would be the first step. That would allow somebody to work on this > >>> at least if Alexey doesn't have time to dive into this deeper. > >>> > >> > >> I didn’t know that repro steps are still not clear. > >> > >> To reproduce the panic you need to have a system, where you can hot add > >> the CPU that belongs to memoryless NUMA node which is not present and onlined > >> yet. In other words, by hot adding CPU, you will add both CPU and NUMA node > >> at the same time. > > > > There seems to be something different in your setup because memory less > > nodes have reportedly worked on x86. I suspect something must be > > different in your setup. Maybe it is that you are adding a cpu that is > > outside of possible cpus intialized during boot time. Those should have > > their nodes initialized properly - at least per init_cpu_to_node. Your > > report doesn't really explain how the cpu is hotadded. Maybe you are > > trying to do something that has never been supported on x86. > Memoryless nodes are supported by x86. But hot add of such nodes not quite > done. > I need some clarification here. It sounds like memoryless nodes work on x86, but hotplug + memoryless nodes isn't a supported use case or you're introducing it as a new use case? If this is a new use case, then I'm inclined to say this patch should NOT go in and a proper fix should be implemented on hotplug's side. I don't want to be in the business of having/seeing this conversation reoccur because we just papered over this issue in percpu. Thanks, Dennis
