Re: [PATCH v5 7/7] fs/resctrl: Document tasks file behaviour for task id 0 and idle tasks

[Reinette Chatre]

Hi Ben,

On 4/28/26 6:04 AM, Ben Horgan wrote:
> When 0 is written to the tasks file it is interpreted as the current task
> in rdtgroup_move_task(). Each CPU's idle task has task_struct::pid set to 0
> and, on x86, task_struct::closid to RESCTRL_RESERVED_CLOSID and
> task_struct::rmid to RESCTRL_RESERVED_RMID. Equivalently, on MPAM
> platforms, thread_info::mpam_partid_pmg is encoded with PARTID and PMG set
> to RESCTRL_RESERVED_CLOSID and RESCTRL_RESERVED_RMID, respectively. As
> there is no interface to change these from the default, the resctrl
> configuration for the idle tasks is fixed and they always behave
> equivalently to a task in the default tasks file and so take their
> configuration from the cpus/cpus_list files.
> 
> On read of the tasks file, show_rdt_tasks() filters out any 0 PID. Hence, a
> task id of 0 is never shown in the tasks file and the idle tasks are not
> represented either.
> 
> Document the user visible behaviour.
> 
> Signed-off-by: Ben Horgan <ben.horgan@xxxxxxx>
> ---

Thank you very much for adding this.

Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>

Reinette