Re: [PATCH v2 2/2] sched/deadline: Reject debugfs dl_server writes for inactive CPUs

[Juri Lelli <juri.lelli@redhat.com>]

Hello,

On 20/09/26 00:31, Hui Su wrote:
> Commit 4043f5498416 ("sched/deadline: Reject debugfs dl_server writes
> for offline CPUs") rejects per-CPU DL server parameter updates once the
> target CPU is offline.
> 
> During CPU hot-unplug, however, the CPU is cleared from cpu_active_mask
> before it is marked offline. This leaves a window where the CPU is no
> longer active but cpu_online() still returns true, so
> sched_server_write_common() continues to accept DL server updates.
> 
> There is no meaningful reason to reconfigure a per-CPU DL server once the
> CPU is being deactivated. Reject the write when the target CPU is inactive
> rather than only after it becomes offline.
> 
> Fixes: d741f297bcea ("sched/fair: Fair server interface")

Isn't 4043f5498416 ("sched/deadline: Reject debugfs dl_server writes for
offline CPUs") more appropriate?

> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Link: https://lore.kernel.org/r/anw7IML1xzHys6re@jlelli-thinkpadt14gen4.remote.csb
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Hui Su <sh_def@163.com>
> ---

Apart from that the fix looks good to me.

Acked-by: Juri Lelli <juri.lelli@redhat.com>

Thanks,
Juri