Re: [PATCH 1/2] cpuset: Fix cpuset_cpus_allowed() to not filter offline CPUs

[Peter Zijlstra]

On Tue, Jan 31, 2023 at 11:14:27PM -0500, Waiman Long wrote:

> A major concern I have is the overhead of creating a poor man version of v2
> cpus_allowed. This issue can be worked around even for cpuset v1 if it is
> mounted with the cpuset_v2_mode option to behave more like v2 in its cpumask
> handling. Alternatively we may be able to provide a config option to make
> this the default for v1 without the special mount option, if necessary.

It is equally broken for v2, it masks against effective_cpus. Not to
mention it explicitly starts with cpu_online_mask.