Messages in this thread | | | Date | Sat, 11 Jul 2009 10:01:54 +0200 | From | Ingo Molnar <> | Subject | Re: Bug in SCHED_IDLE interaction with group scheduling? |
| |
* Paul Turner <pjt@google.com> wrote:
> Hi Peter, > > It seems like there's an assumption in the sched_idle policy check in > place_entity that the sched_entity we are looking at belongs to a task? > > - Paul > > -- > > sched: bug in SCHED_IDLE interaction with group scheduling > > One of the isolation modifications for SCHED_IDLE is the > unitization of sleeper credit. However the check for this assumes > that the sched_entity we're placing always belongs to a task. > > This is potentially not true with group scheduling and leaves us > rummaging randomly when we try to pull the policy. > > Signed-off-by: Paul Turner <pjt@google.com> > --- > kernel/sched_fair.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c > index ba7fd6e..7c248dc 100644 > --- a/kernel/sched_fair.c > +++ b/kernel/sched_fair.c > @@ -687,7 +687,8 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) > * all of which have the same weight. > */ > if (sched_feat(NORMALIZED_SLEEPER) && > - task_of(se)->policy != SCHED_IDLE) > + (!entity_is_task(se) || > + task_of(se)->policy != SCHED_IDLE)) > thresh = calc_delta_fair(thresh, se);
Ah, nice catch!
( Sidenote: we keep having these subtle bugs where we call task_of(se) on a non-task entity - it's been the fifth such incident or so. Perhaps we should add an active debug check to task_of(), in the case of CONFIG_SCHED_DEBUG=y. )
Ingo
| |