Messages in this thread |  | | | Date | Thu, 20 Nov 2008 08:58:29 +0100 | | From | Ingo Molnar <> | | Subject | Re: [PATCH] sched: Don't allow priority switch to realtime when the task doesn't belong to init_task_group and when CONFIG_RT_GROUP_SCHED isn't set | |
* Bharata B Rao <bharata@linux.vnet.ibm.com> wrote:
> Applies on 2.6.28-rc5.> > With CONFIG_RT_GROUP_SCHED not set, don't allow a task's priority
> switch to realtime if the task isn't part of init_task_group.
> > A task belonging to a fair group could use > sched_setscheduler/sched_setparam to become a realtime task. If such
> a task belongs to one of the child groups of init_task_group and if
> CONFIG_RT_GROUP_SCHED is not set, then it ends up getting queued in
> init_task_group's runqueue. So we have a situation where, a task
> belongs to one group (child) but ends in the runqueue of another
> group (init_task_group). This does not look correct.
> > Fix this by failing such priority change requests in
> sched_setscheduler() and sched_setparam().> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
> kernel/sched.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -5206,6 +5206,13 @@ recheck:
> if (rt_bandwidth_enabled() && rt_policy(policy) &&
> task_group(p)->rt_bandwidth.rt_runtime == 0)
> return -EPERM;
> +#elif defined(CONFIG_FAIR_GROUP_SCHED)
> + /*
> + * If the task doesn't belong to init_task_group, don't
> + * allow priority switch to realtime. (!CONFIG_RT_GROUP_SCHED)
> + */
> + if (rt_policy(policy) && (task_group(p) != &init_task_group))
> + return -EPERM;
> #endif
>
> retval = security_task_setscheduler(p, policy, param);
hm, another option would be, instead of denying something (which
denial might not even be noticed by the app) that the app clearly has
enough privilege to request - to just act upon it and move the task to
the init_task_group?
the app cannot expect fair scheduling for this task anyway. And if we
want to forbid tasks from doing so - do not give them privilege to go
to RT priorities.
Ingo
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