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SubjectRe: [PATCH] cgroups: respect cgroup timer slack value in prctl
On Tue, Feb 01, 2011 at 11:07:43PM -0800, Matt Helsley wrote:
> On Tue, Feb 01, 2011 at 02:41:43PM -0800, jacob.jun.pan@linux.intel.com wrote:
> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> >
> > Per cgroup timer slack value is used to manage task groups
> > for more friendly power management behavior. Once a task is
> > attached to a cgroup, we should not allow user to change
> > (escape) the per cgroup restriction unless a more relaxed
> > timer slack value is given by user via prctl.
> >
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
>
> > ---
> > include/linux/cgroup.h | 13 +++++++++++++
>
> Looks like the original two patches (one or more implementing:
>
> > kernel/cgroup_timer_slack.c | 4 ----
>
> ) were not sent to containers@lists.linux-foundation.org ?

Hm..

https://lists.linux-foundation.org/pipermail/containers/2011-February/026415.html

>
> > kernel/sys.c | 21 ++++++++++++++++++++-
> > 3 files changed, 33 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> > index ed4ba11..4405666 100644
> > --- a/include/linux/cgroup.h
> > +++ b/include/linux/cgroup.h
> > @@ -627,6 +627,19 @@ bool css_is_ancestor(struct cgroup_subsys_state *cg,
> > unsigned short css_id(struct cgroup_subsys_state *css);
> > unsigned short css_depth(struct cgroup_subsys_state *css);
> >
> > +#ifdef CONFIG_CGROUP_TIMER_SLACK
> > +struct timer_slack_cgroup {
> > + struct cgroup_subsys_state css;
> > + unsigned long timer_slack_ns;
> > +};
> > +
> > +static inline struct timer_slack_cgroup *task_timer_slack(struct task_struct *task)
> > +{
> > + return container_of(task_subsys_state(task, timer_slack_subsys_id),
> > + struct timer_slack_cgroup, css);
> > +}
> > +#endif
> > +
> > #else /* !CONFIG_CGROUPS */
> >
> > static inline int cgroup_init_early(void) { return 0; }
> > diff --git a/kernel/cgroup_timer_slack.c b/kernel/cgroup_timer_slack.c
> > index daa452d..1de122a 100644
> > --- a/kernel/cgroup_timer_slack.c
> > +++ b/kernel/cgroup_timer_slack.c
> > @@ -4,10 +4,6 @@
> > #include <linux/slab.h>
> >
> > struct cgroup_subsys timer_slack_subsys;
> > -struct timer_slack_cgroup {
> > - struct cgroup_subsys_state css;
> > - unsigned long timer_slack_ns;
> > -};
> >
> > static struct timer_slack_cgroup *cgroup_to_tslack_cgroup(struct cgroup *cgroup)
> > {
> > diff --git a/kernel/sys.c b/kernel/sys.c
> > index 7f5a0cd..433fcdb 100644
> > --- a/kernel/sys.c
> > +++ b/kernel/sys.c
> > @@ -37,6 +37,8 @@
> > #include <linux/ptrace.h>
> > #include <linux/fs_struct.h>
> > #include <linux/gfp.h>
> > +#include <linux/cgroup.h>
> > +#include <linux/init_task.h>
> >
> > #include <linux/compat.h>
> > #include <linux/syscalls.h>
> > @@ -1688,8 +1690,25 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
> > if (arg2 <= 0)
> > current->timer_slack_ns =
> > current->default_timer_slack_ns;
> > - else
> > + else {
> > +#ifdef CONFIG_CGROUP_TIMER_SLACK
> > + /* only allow more relaxed slack value than
> > + * the attached timer slack cgroup allows.
> > + */
> > + unsigned long cg_timer_slack;
> > +
> > + rcu_read_lock();
> > + cg_timer_slack = task_timer_slack(current)->timer_slack_ns;
> > + rcu_read_unlock();
> > + if (cg_timer_slack < arg2 || cg_timer_slack
> > + == TIMER_SLACK_NS_DEFAULT)
> > + current->timer_slack_ns = arg2;
> > + else
> > + return -EINVAL;
> > +#else
>
> Looks like this could be an inline function which returns the
> minimum timer slack allowed for the task. Then the code here would be:
>
> if (arg2 <= 0)
> current->timer_slack_ns = current->default_timer_slack_ns;
> else {
> if (arg2 < min_timer_slack_ns(tsk))
> return -EINVAL; /* Can't set less than the minimum */
> current->timer_slack_ns = arg2;
> }
>
> and the #ifdef CONFIG_CGROUP_TIMER_SLACK bits could be in a header as
> usual.
>
> Incidentally, shouldn't that really be -EPERM since it's not an invalid
> value -- just one that's not permitted due to restrictions imposed by
> the cgroup subsystem?

I guess better to add more functionality to the cgroup subsystem.
I'm going to implement timer_slack.min_slack_ns and timer_slack.max_slack_ns.
prctl(2) will be modified to check these limits.


> > current->timer_slack_ns = arg2;
> > +#endif
> > + }
> > error = 0;
> > break;
> > case PR_MCE_KILL:
> > --
> > 1.7.0.4
> >
> > _______________________________________________
> > Containers mailing list
> > Containers@lists.linux-foundation.org
> > https://lists.linux-foundation.org/mailman/listinfo/containers

--
Kirill A. Shutemov


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