Hi Luca, On 15/10/15 12:09, Luca Abeni wrote: > Commit 9d5142624256 ("sched/deadline: Reduce rq lock contention by > eliminating locking of non-feasible target") broke select_task_rq_dl() > and find_lock_later_rq(), because it introduced a comparison between > the local task's deadline and dl.earliest_dl.curr of the remote queue. > However, if the remote runqueue does not contain any SCHED_DEADLINE > task its earliest_dl.curr is 0 (always smaller than the deadline of > the local task) and the remote runqueue is not selected for pushing. > As a result, if an application creates multiple SCHED_DEADLINE threads, > they will never be pushed to runqueues that do not already contain > SCHED_DEADLINE tasks. > This patches fixes the issue by checking if dl.earliest_dl.curr == 0. > > Signed-off-by: Luca Abeni <luca.ab...@unitn.it> > --- > kernel/sched/deadline.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index fc8f010..0d86d60 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -1066,8 +1066,9 @@ select_task_rq_dl(struct task_struct *p, int cpu, int > sd_flag, int flags) > int target = find_later_rq(p); > > if (target != -1 && > - dl_time_before(p->dl.deadline, > - cpu_rq(target)->dl.earliest_dl.curr)) > + (dl_time_before(p->dl.deadline, > + cpu_rq(target)->dl.earliest_dl.curr) || > + (cpu_rq(target)->dl.earliest_dl.curr == 0)))
Can't we actually use dl.dl_nr_running here and below, so that we won't incur any wraparound problem? Thanks, - Juri > cpu = target; > } > rcu_read_unlock(); > @@ -1417,7 +1418,8 @@ static struct rq *find_lock_later_rq(struct task_struct > *task, struct rq *rq) > > later_rq = cpu_rq(cpu); > > - if (!dl_time_before(task->dl.deadline, > + if (later_rq->dl.earliest_dl.curr && > + !dl_time_before(task->dl.deadline, > later_rq->dl.earliest_dl.curr)) { > /* > * Target rq has tasks of equal or earlier deadline, > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/