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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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