On 12/10/21 2:05 PM, enh wrote:
> On Fri, Dec 10, 2021 at 3:46 AM Rob Landley <[email protected]
> Could you ask them what uclamp_validate() in kernel/sched/core.c is
> trying to
> do? It seems like if you've set container limits for the largest or
> smallest
> allowed uclamp values (like that wiki page was going on about). then it
> checks
> THOSE instead of the ones provided by the user to see if they cross.
> Overwrites
> the ones provided by the user entirely, and doesn't check them. So I
> THINK if I
> set the container min limit to 1 and the container max limit to 1023, I
> could
> then have a process within the container request a min of 1000 and a max
> of 100
> and it would pass this function? (Or am I misreading it?)
>
> i must be misreading it too, because i don't even know which lines you're
> referring to, unless we were looking at different versions...
> https://elixir.bootlin.com/linux/latest/source/kernel/sched/core.c#L1780
Yup, that part:
static int uclamp_validate(struct task_struct *p,
const struct sched_attr *attr)
{
int util_min = p->uclamp_req[UCLAMP_MIN].value;
int util_max = p->uclamp_req[UCLAMP_MAX].value;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
util_min = attr->sched_util_min;
if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
return -EINVAL;
}
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
util_max = attr->sched_util_max;
if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
return -EINVAL;
}
if (util_min != -1 && util_max != -1 && util_min > util_max)
return -EINVAL;
See how util_min is set from uclamp_req at the start, but when
SCHED_FLAG_UTIL_CLAMP_MIN the local variable gets overwritten by the attr->
version, and there's only one util_min > util_max test?
If SCHED_FLAG_UTIIL_CLAMP_BLAH is set, the uclamp_req versions of sched_util_min
and sched_util_max are never examined by this function. Just fetched and then
overwritten.
I.E:
static int uclamp_validate(struct task_struct *p,
const struct sched_attr *attr)
{
int util_min = p->uclamp_req[UCLAMP_MIN].value;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
util_min = attr->sched_util_min;
if (test util_min)
return -EINVAL;
Rob
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