Messages in this thread |  | | Date | Thu, 20 Nov 2008 09:17:32 +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 |
| |
* Dhaval Giani <dhaval@linux.vnet.ibm.com> wrote:
> On Thu, Nov 20, 2008 at 08:58:29AM +0100, Ingo Molnar wrote: > > > > * 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. > > > > I am wondering what would the right action then be if the task drops > back to CFS.
yeah. If the integration artifacts around the edges get too awkward, then the best would be to consolidate fair-group and rt-group into the same group-sched config option and _eliminate_ such artifacts at their root. rt-group was started as a separate option mostly because it was new and experimental code - that splitup is not cast into stone.
Ingo
|  |