On 19/07/2019 08:34, Juri Lelli wrote: > On !CONFIG_RT_GROUP_SCHED configurations it is currently not possible to > move RT tasks between cgroups to which cpu controller has been attached; > but it is oddly possible to first move tasks around and then make them > RT (setschedule to FIFO/RR). > > E.g.: > > # mkdir /sys/fs/cgroup/cpu,cpuacct/group1 > # chrt -fp 10 $$ > # echo $$ > /sys/fs/cgroup/cpu,cpuacct/group1/tasks > bash: echo: write error: Invalid argument > # chrt -op 0 $$ > # echo $$ > /sys/fs/cgroup/cpu,cpuacct/group1/tasks > # chrt -fp 10 $$ > # cat /sys/fs/cgroup/cpu,cpuacct/group1/tasks > 2345 > 2598 > # chrt -p 2345 > pid 2345's current scheduling policy: SCHED_FIFO > pid 2345's current scheduling priority: 10 > > Also, as Michal noted, it is currently not possible to enable cpu > controller on unified hierarchy with !CONFIG_RT_GROUP_SCHED (if there > are any kernel RT threads in root cgroup, they can't be migrated to the > newly created cpu controller's root in cgroup_update_dfl_csses()). > > Existing code comes with a comment saying the "we don't support RT-tasks > being in separate groups". Such comment is however stale and belongs to > pre-RT_GROUP_SCHED times. Also, it doesn't make much sense for > !RT_GROUP_ SCHED configurations, since checks related to RT bandwidth > are not performed at all in these cases. > > Make moving RT tasks between cpu controller groups viable by removing > special case check for RT (and DEADLINE) tasks. > > Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx> > Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx> Reviewed-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Thanks! -- Daniel
