Re: [PATCH v2 01/21] sched: Reject SCHED_FLAG_KEEP_PARAMS before reserving deadline bandwidth

[Juri Lelli]

Hello,

On 04/11/26 16:11, Mathieu Desnoyers wrote:
> __sched_setscheduler() returns -EINVAL for a SCHED_FLAG_KEEP_PARAMS
> request that would change scheduling class, after sched_dl_overflow()
> has reserved the bandwidth of the request, and nothing gives it back.
> Switching a SCHED_OTHER task to SCHED_DEADLINE that way fails and leaks
> the runtime that sched_setattr() filled in from the task's slice, up to
> 100ms with a custom one, into the root domain's total_bw. Repeated, it
> makes the root domain refuse every deadline task, and refuse to offline
> its last CPU.
> 
> Reserve the bandwidth after that check, last of the checks. A refused
> request also leaves sched_reset_on_fork as it was again.
> 
> Fixes: 8a70415351ba ("sched: Reject SCHED_FLAG_KEEP_PARAMS when it would change scheduling class")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> ---

Makes sense to me.

Reviewed-by: Juri Lelli <juri.lelli@xxxxxxxxxx>

Thanks,
Juri