Re: Oops on Power8 (was Re: [PATCH v2 1/7] workqueue: make workqueue available early during boot)

Balbir Singh [off-list ref] writes:

On 17/10/16 23:24, Michael Ellerman wrote:

quoted

That happened because we haven't yet called set_cpu_numa_node() for the non-boot
cpus, because that happens in smp_prepare_cpus(), and
workqueue_init_early() is called much earlier than that.

This doesn't trigger on x86 because it does set_cpu_numa_node() in
setup_per_cpu_areas(), which is called prior to workqueue_init_early().

We can (should) probably do the same on powerpc, I'll look at that
tomorrow. But other arches may have a similar problem, and at the very
least we need to document that workqueue_init_early() relies on
cpu_to_node() working.

Don't we do the setup cpu->node mapings in initmem_init()?
Ideally we have setup_arch->intmem_init->numa_setup_cpu

That sets up numa_cpu_lookup_table, which is a powerpc only data
structure.

But it doesn't setup the percpu numa_node variables, used by
cpu_to_node(), because percpu areas are not setup yet.

cheers