sched: Fix rt_task to work properly
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Thank you for your immediate response.
Quoted 9 lines
AFAICS this change is a larger layer violation (dependency issue) since AFAIK
prio.his a generic, common base header which is to provide priority definitions
common to *all* of the
more specific scheduler sub handling
(deadline, rt, ...),
which thus should not have to aggregate
any specific knowledge whatsoever about
various scheduler sub type specific handling.
We agree that the prio.h file has to be generic, but we thought that adding the priority information of deadline scheduler (i.e., #define MAX_DL_PRIO 0) to this file should be fine, because prio.h already has the priority information for cfs and rt schedulers (i.e., MAX_PRIO and MAX_RT_PRIO).
Quoted 8 lines
rt_prio()quite likely is to be seen as an *rt-specific* API since it is defined in the *rt-specific*rt.hheader.
IOW,rt_prio()is *not to be used* for any areas where we
do not have an RT case
(quite certainly header docs should be added tort_prio()
to definitely emphasize this fact,
maybe something like
"Note that since this is an RT API it is meaningful for RT tasks only").
The rt_prio() function returns 1 or 0 according to whether or not the corresponding process is an rt task. Thus, we believe that rt_prio() is a suitable function to determine if a task is rt one, and can be called even for non-rt tasks. Indeed we can easily find examples where rt_prio()/rt_task() is called for an arbitrary process without limiting to rt tasks (e.g., sched_fork()).
Though our initial intention was to fix the origin of the problem, if you/we are not convinced of our patch due to dependency issues, we can reinforce the conditional statement in tg_has_rt_tasks() by adding !dl_task(p) as follows:
if (!dl_task(p) && rt_task(p) && task_group(p) == tg)
In this manner, we can avoid modifying the header files in include/linux/sched/, while having the same effect with respect to cgroup.
Thanks,
Yin-goo Yim