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    SubjectRe: [patch 02/15] sched: validate CFS quota hierarchies
    (2011/03/23 12:03), Paul Turner wrote:
    > @@ -9251,7 +9255,13 @@ static int tg_set_cfs_bandwidth(struct t
    > if (period > max_cfs_quota_period)
    > return -EINVAL;
    >
    > - mutex_lock(&mutex);
    > + mutex_lock(&cfs_constraints_mutex);
    > + if (sysctl_sched_cfs_bandwidth_consistent) {
    > + ret = __cfs_schedulable(tg, period, quota);

    At this point:
    period => scale in ns unit
    quota => scale in ns unit, or RUNTIME_INF

    And both are unsigned. But...

    > @@ -9339,6 +9350,108 @@ static int cpu_cfs_period_write_u64(stru
    > return tg_set_cfs_period(cgroup_tg(cgrp), cfs_period_us);
    > }
    >
    > +
    > +struct cfs_schedulable_data {
    > + struct task_group *tg;
    > + u64 period, quota;
    > +};
    > +
    > +/*
    > + * normalize group quota/period to be quota/max_period
    > + * note: units are usecs
    > + */
    > +static u64 normalize_cfs_quota(struct task_group *tg,
    > + struct cfs_schedulable_data *d)
    > +{
    > + u64 quota, period;
    > + struct load_weight lw;
    > +
    > + if (tg == d->tg) {
    > + period = d->period;
    > + quota = d->quota;
    > + } else {
    > + period = tg_get_cfs_period(tg);
    > + quota = tg_get_cfs_quota(tg);
    > + }

    ... at this point:
    period => scale in us unit
    quota => scale in us unit, or -1
    Moreover:
    d->period => (scale in ns unit) / NSEC_PER_USEC
    d->quota => (scale in ns unit, or RUNTIME_INF) / NSEC_PER_USEC

    Therefore, ...

    > +
    > + if (quota == RUNTIME_INF)
    > + return RUNTIME_INF;

    This check doesn't work properly.

    I found this problem because I could not get child group back to be
    unconstrained:

    [root@localhost group0]# cat cpu.cfs_*
    500000
    500000
    [root@localhost group0]# cat sub0/cpu.cfs_*
    500000
    100000
    [root@localhost group0]# cat sub1/cpu.cfs_*
    500000
    100000
    [root@localhost group0]# echo -1 > sub1/cpu.cfs_quota_us
    bash: echo: write error: Invalid argument

    I confirmed that this write error is removed by the following
    change. I'm looking forward to seeing your V6 soon.

    Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>


    Thanks,
    H.Seto

    ---
    kernel/sched.c | 8 ++++----
    1 files changed, 4 insertions(+), 4 deletions(-)

    diff --git a/kernel/sched.c b/kernel/sched.c
    index 6d764b5..c8f9820 100644
    --- a/kernel/sched.c
    +++ b/kernel/sched.c
    @@ -9467,8 +9467,8 @@ static u64 normalize_cfs_quota(struct task_group *tg,
    period = d->period;
    quota = d->quota;
    } else {
    - period = tg_get_cfs_period(tg);
    - quota = tg_get_cfs_quota(tg);
    + period = ktime_to_ns(tg_cfs_bandwidth(tg)->period);
    + quota = tg_cfs_bandwidth(tg)->quota;
    }

    if (quota == RUNTIME_INF)
    @@ -9515,8 +9515,8 @@ static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
    int ret;
    struct cfs_schedulable_data data = {
    .tg = tg,
    - .period = period / NSEC_PER_USEC,
    - .quota = quota / NSEC_PER_USEC,
    + .period = period,
    + .quota = quota,
    };

    if (!sysctl_sched_cfs_bandwidth_consistent)
    --
    1.7.4


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