Re: [PATCH v3 04/12] smp: Use on-stack cpumask in smp_call_function_many_cond

[Sebastian Andrzej Siewior]

On 2026-03-18 12:56:30 [+0800], Chuyi Zhou wrote:
> This patch use on-stack cpumask to replace percpu cfd cpumask in
> smp_call_function_many_cond(). Note that when both CONFIG_CPUMASK_OFFSTACK
> and PREEMPT_RT are enabled, allocation during preempt-disabled section
> would break RT. Therefore, only do this when CONFIG_CPUMASK_OFFSTACK=n.
> This is a preparation for enabling preemption during csd_lock_wait() in
> smp_call_function_many_cond().

You explained why we do this only for !CONFIG_CPUMASK_OFFSTACK but
failed to explain why we need a function local cpumask. Other than
preparation step. But this allocation looks pointless, let me look
further…

> Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
> Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>

Sebastian