Hi Peng, On Sat, Oct 06, 2018 at 06:22:11AM +0800, Peng Hao wrote: > find_lock_lowest_rq may or not releease rq lock when return > lowest_rq=NULL, but it is fuzzy. > If not releasing rq lock, it is unnecessary to re-call > pick_next_pushable_task.
IIRC, deadline.c uses a similar pattern (c.f., find_lock_later_rq() and pick_next_pushable_dl_task()): should it be considered for this change? Andrea > When CONFIG_PREEMPT=n, not releasing rq lock and return > lowest_rq=null frequently happens in a simple test case: > Four different rt priority tasks run on limited two cpus. > Thanks for Steven Rostedt's advice. > > Signed-off-by: Peng Hao <[email protected]> > --- > kernel/sched/rt.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 2e2955a..be0fc43 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1754,7 +1754,7 @@ static struct rq *find_lock_lowest_rq(struct > task_struct *task, struct rq *rq) > !task_on_rq_queued(task))) { > > double_unlock_balance(rq, lowest_rq); > - lowest_rq = NULL; > + lowest_rq = RETRY_TASK; > break; > } > } > @@ -1830,7 +1830,9 @@ static int push_rt_task(struct rq *rq) > > /* find_lock_lowest_rq locks the rq if found */ > lowest_rq = find_lock_lowest_rq(next_task, rq); > - if (!lowest_rq) { > + if (!lowest_rq) > + goto out; > + if (lowest_rq == RETRY_TASK) { > struct task_struct *task; > /* > * find_lock_lowest_rq releases rq->lock > -- > 1.8.3.1 >
