Re: [PATCH v2] NUMA: Early use of cpu_to_node() returns 0 instead of the correct node id

[Shijie Huang]

在 2024/1/25 1:19, Lameter, Christopher 写道:
> On Tue, 23 Jan 2024, Huang Shijie wrote:
>
> > During the kernel booting, the generic cpu_to_node() is called too 
> > early in
> > arm64, powerpc and riscv when CONFIG_NUMA is enabled.
> >
> > For arm64/powerpc/riscv, there are at least four places in the common 
> > code
> > where the generic cpu_to_node() is called before it is initialized:
> >        1.) early_trace_init()         in kernel/trace/trace.c
> >        2.) sched_init()               in kernel/sched/core.c
> >        3.) init_sched_fair_class()    in kernel/sched/fair.c
> >        4.) workqueue_init_early()     in kernel/workqueue.c
> >
> > In order to fix the bug, the patch changes generic cpu_to_node to
> > function pointer, and export it for kernel modules.
> > Introduce smp_prepare_boot_cpu_start() to wrap the original
> > smp_prepare_boot_cpu(), and set cpu_to_node with early_cpu_to_node.
> > Introduce smp_prepare_cpus_done() to wrap the original 
> > smp_prepare_cpus(),
> > and set the cpu_to_node to formal _cpu_to_node().
>
> Would  you please fix this cleanly without a function pointer?
>
> What I think needs to be done is a patch series.
>
> 1. Instrument cpu_to_node so that some warning is issued if it is used 
> too early. Preloading the array with NUMA_NO_NODE would allow us to do 
> that.
>
> 2. Implement early_cpu_to_node on platforms that currently do not have 
> it.
>
> 3. A series of patches that fix each place where cpu_to_node is used 
> too early.

okay, I will try to do it.


Thanks

Huang Shijie