Re: [PATCH v5 05/12] smp: Alloc percpu csd data in smpcfd_prepare_cpu() only once

[Muchun Song]

> On Apr 22, 2026, at 14:40, Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> wrote:
> 
> Later patch would enable preemption during csd_lock_wait() in
> smp_call_function_many_cond(), which may cause access cfd->csd data that
> has already been freed in smpcfd_dead_cpu().
> 
> One way to fix the above issue is to use the RCU mechanism to protect the
> csd data and wait for all read critical sections to exit before freeing
> the memory in smpcfd_dead_cpu(), but this could delay CPU shutdown. This
> patch chooses a simpler approach: allocate the percpu csd on the UP side
> only once and skip freeing the csd memory in smpcfd_dead_cpu().
> 
> Suggested-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>

Acked-by: Muchun Song <muchun.song@xxxxxxxxx>

Thanks.