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SubjectRe: [PATCH v4 3/4] sched: Allow sched_{get,set}attr to change latency_nice of the task
On Mon, Feb 24, 2020 at 02:29:17PM +0530, Parth Shah wrote:

[...]

> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 65b6c00d6dac..e1dc536d4ca3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -4723,6 +4723,8 @@ static void __setscheduler_params(struct task_struct *p,
> p->rt_priority = attr->sched_priority;
> p->normal_prio = normal_prio(p);
> set_load_weight(p, true);
> +
> + p->latency_nice = attr->sched_latency_nice;
> }

We don't want this when SCHED_FLAG_LATENCY_NICE is not set in
attr->flags.

The user may pass SCHED_FLAG_KEEP_PARAMS | SCHED_FLAG_LATENCY_NICE to
change only latency nice value. So we have to update latency_nice
outside __setscheduler_params(), I think.

>
> /* Actually do priority change: must hold pi & rq lock. */
> @@ -4880,6 +4882,13 @@ static int __sched_setscheduler(struct task_struct *p,
> return retval;
> }
>
> + if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE) {
> + if (attr->sched_latency_nice > MAX_LATENCY_NICE)
> + return -EINVAL;
> + if (attr->sched_latency_nice < MIN_LATENCY_NICE)
> + return -EINVAL;
> + }
> +
> if (pi)
> cpuset_read_lock();
>
> @@ -4914,6 +4923,9 @@ static int __sched_setscheduler(struct task_struct *p,
> goto change;
> if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
> goto change;
> + if (attr->sched_flags & SCHED_FLAG_LATENCY_NICE &&
> + attr->sched_latency_nice != p->latency_nice)
> + goto change;
>
> p->sched_reset_on_fork = reset_on_fork;
> retval = 0;
> @@ -5162,6 +5174,9 @@ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *a
> size < SCHED_ATTR_SIZE_VER1)
> return -EINVAL;
>
> + if ((attr->sched_flags & SCHED_FLAG_LATENCY_NICE) &&
> + size < SCHED_ATTR_SIZE_VER2)
> + return -EINVAL;
> /*
> * XXX: Do we want to be lenient like existing syscalls; or do we want
> * to be strict and return an error on out-of-bounds values?
> @@ -5391,6 +5406,8 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
> else
> kattr.sched_nice = task_nice(p);
>
> + kattr.sched_latency_nice = p->latency_nice;
> +

Can you consider printing latency_nice value in proc_sched_show_task() in this
patch/series?

Thanks,
Pavan

--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

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