On Sun, 17 Jan 2021 at 13:31, Jiang Biao <[email protected]> wrote: > > From: Jiang Biao <[email protected]> > > delta in update_stats_wait_end() might be negative, which would > make following statistics go wrong.
Could you describe the use case that generates a negative delta ? rq_clock is always increasing so this should not lead to a negative value even if update_stats_wait_end/start are not called in the right order, This situation could happen after a migration if we forgot to call update_stats_wait_start > > Add protection for delta of wait time, like what have been done in > update_stats_enqueue_sleeper() for deltas of sleep/block time. > > Signed-off-by: Jiang Biao <[email protected]> > --- > kernel/sched/fair.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c0374c1152e0..ac950ac950bc 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -917,6 +917,9 @@ update_stats_wait_end(struct cfs_rq *cfs_rq, struct > sched_entity *se) > > delta = rq_clock(rq_of(cfs_rq)) - > schedstat_val(se->statistics.wait_start); > > + if ((s64)delta < 0) > + delta = 0; > + > if (entity_is_task(se)) { > p = task_of(se); > if (task_on_rq_migrating(p)) { > -- > 2.21.0 >
