Re: [PATCH v3 3/4] cpuset: settle isolation state when CPUs are given back to parent

[Guopeng Zhang]

在 2026/11/7 20:00, Ridong Chen 写道:
> From: Ridong Chen <chenridong@xxxxxxxxxx>
> 
> partition_xcpus_del() only updates isolated_cpus when the partition that
> gives back the CPUs has a different state than its parent. CPUs that were
> further distributed to descendant isolated partitions are not taken into
> account, so isolated_cpus_release() has to be called afterwards in
> several places to walk up the ancestors and fix isolated_cpus.
> 
> Make partition_xcpus_del() always set the isolation state of the given
> back CPUs to the state of the parent that receives them. As the
> effective_xcpus of a partition covers the CPUs distributed to its
> descendants, the isolation state of those CPUs is settled at the same
> time. Boot-time isolated CPUs are still preserved by isolated_cpu_update().
> 
> compute_partition_effective_cpumask() invalidates a child partition
> without going through partition_xcpus_del(), so do the same there: the
> CPUs of the invalidated child take the isolation state of its parent.
> 
> As the parent may be shrunk and its effective_xcpus not updated yet,
> only do so for the CPUs the parent still owns. This is to keep the
> isolation state correct for now, the in-place invalidation here will be
> removed later in the partition rework.
> 
> isolated_cpus_update() assumes the old and new states are different,
> which no longer holds now that partition_xcpus_del() proceeds regardless
> of the states. Drop its @old_prs argument and the WARN_ON_ONCE() so that
> it simply sets the isolation state of the given CPUs, and use it
> everywhere. The state check in partition_xcpus_add() is dropped as well,
> as setting the state is a no-op when the states are the same.
> 
> isolated_cpus_release() is no longer needed and is removed.
> 

Hi Ridong,

Would it be worth briefly mentioning in the commit message that this patch also fixes the issue described here?

https://lore.kernel.org/all/20261105130344.664336-4-guopeng.zhang@xxxxxxxxx/

Thanks,
Guopeng