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Keep this check last. If a later check failed, >> * nothing would give back the bandwidth it reserves. >> + * >> + * With SCHED_FLAG_KEEP_PARAMS, the task keeps its parameters, so >> + * there is nothing to admit. The parameters in attr may also be >> + * stale: sys_sched_setattr() read them from the task without a lock. > > However I had to wonder what usecase would still make sense for a > KEEP_PARAMS call on a SCHED_DEADLINE task, I would say a !DL params > change (UCLAMP for example) for a (at the moment) DEADLINE task that > might become !DEADLINE in the future? Maybe we could add this to the > comment. Yes, that is the case I see too. The deadline class does not set uclamp_enabled, but __setscheduler_uclamp() stores the clamps for any class. I will extend the comment in the next version: * With SCHED_FLAG_KEEP_PARAMS, the task keeps its parameters, so * there is nothing to admit. Such a call changes other attributes, * such as the utilization clamps. A deadline task does not use its * clamps, but keeps them for when it leaves the class. The * parameters in attr may also be stale: sys_sched_setattr() read * them from the task without a lock. Thanks for the review! Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com