Re: [PATCH 13/33] cpuset: Update HK_TYPE_DOMAIN cpumask from cpuset

[Waiman Long]

On 11/5/25 10:45 AM, Frederic Weisbecker wrote:
> > > +	if (!trial)
> > > +		return -ENOMEM;
> > > +
> > > +	cpumask_andnot(trial, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT), mask);
> > > +	if (!cpumask_intersects(trial, cpu_online_mask)) {
> > > +		kfree(trial);
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	if (!housekeeping.flags)
> > > +		static_branch_enable(&housekeeping_overridden);
> > > +
> > > +	if (!(housekeeping.flags & BIT(type)))
> > > +		old = housekeeping_cpumask_dereference(type);
> > > +	else
> > > +		WRITE_ONCE(housekeeping.flags, housekeeping.flags | BIT(type));
> > > +	rcu_assign_pointer(housekeeping.cpumasks[type], trial);
> > > +
> > > +	synchronize_rcu();
> > > +
> > > +	kfree(old);
> > If "isolcpus" boot command line option is set, old can be a pointer to the
> > boot time memblock area which isn't a pointer that can be handled by the
> > slab allocator AFAIU. I don't know the exact consequence, but it may not be
> > good. One possible solution I can think of is to make HK_TYPE_DOMAIN and
> > HK_TYPE_DOMAIN_ROOT point to the same memblock pointer and don't pass the
> > old HK_TYPE_DOMAIN pointer to kfree() if it matches HK_TYPE_DOMAIN_BOOT one.
> > Alternatively, we can just set the HK_TYPE_DOMAIN_BOOT pointer at boot and
> > make HK_TYPE_DOMAIN falls back to HK_TYPE_DOMAIN_BOOT if not set.
> Have a look at housekeeping_init() which reallocates the memblock
> allocated memory with kmalloc to avoid these troubles.

Ah your previous patch of this series did that. I was thinking about the 
existing kernel code at the time. So you can ignore that comment.

Thanks,
Longman