Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 17 Aug 2022 17:08:10 +0200 | Subject | Re: [PATCH v4 6/9] sched/fair: fix another detach on unattached task corner case |
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On Wed, 17 Aug 2022 at 17:04, Chengming Zhou <zhouchengming@bytedance.com> wrote: > > On 2022/8/17 23:01, Vincent Guittot wrote: > > On Mon, 8 Aug 2022 at 14:58, Chengming Zhou <zhouchengming@bytedance.com> wrote: > >> > >> commit 7dc603c9028e ("sched/fair: Fix PELT integrity for new tasks") > >> fixed two load tracking problems for new task, including detach on > >> unattached new task problem. > >> > >> There still left another detach on unattached task problem for the task > >> which has been woken up by try_to_wake_up() and waiting for actually > >> being woken up by sched_ttwu_pending(). > >> > >> try_to_wake_up(p) > >> cpu = select_task_rq(p) > >> if (task_cpu(p) != cpu) > >> set_task_cpu(p, cpu) > >> migrate_task_rq_fair() > >> remove_entity_load_avg() --> unattached > >> se->avg.last_update_time = 0; > >> __set_task_cpu() > >> ttwu_queue(p, cpu) > >> ttwu_queue_wakelist() > >> __ttwu_queue_wakelist() > >> > >> task_change_group_fair() > >> detach_task_cfs_rq() > >> detach_entity_cfs_rq() > >> detach_entity_load_avg() --> detach on unattached task > >> set_task_rq() > >> attach_task_cfs_rq() > >> attach_entity_cfs_rq() > >> attach_entity_load_avg() > >> > >> The reason of this problem is similar, we should check in detach_entity_cfs_rq() > >> that se->avg.last_update_time != 0, before do detach_entity_load_avg(). > >> > >> This patch move detach/attach_entity_cfs_rq() functions up to be together > >> with other load tracking functions to avoid to use another #ifdef CONFIG_SMP. > >> > >> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> > >> --- > >> kernel/sched/fair.c | 132 +++++++++++++++++++++++--------------------- > >> 1 file changed, 68 insertions(+), 64 deletions(-) > >> > >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >> index f52e7dc7f22d..4bc76d95a99d 100644 > >> --- a/kernel/sched/fair.c > >> +++ b/kernel/sched/fair.c > >> @@ -874,9 +874,6 @@ void init_entity_runnable_average(struct sched_entity *se) > >> void post_init_entity_util_avg(struct task_struct *p) > >> { > >> } > >> -static void update_tg_load_avg(struct cfs_rq *cfs_rq) > >> -{ > >> -} > >> #endif /* CONFIG_SMP */ > >> > >> /* > >> @@ -3176,6 +3173,7 @@ void reweight_task(struct task_struct *p, int prio) > >> load->inv_weight = sched_prio_to_wmult[prio]; > >> } > >> > >> +static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq); > >> static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); > >> > >> #ifdef CONFIG_FAIR_GROUP_SCHED > >> @@ -4086,6 +4084,71 @@ static void remove_entity_load_avg(struct sched_entity *se) > >> raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags); > >> } > >> > >> +#ifdef CONFIG_FAIR_GROUP_SCHED > >> +/* > >> + * Propagate the changes of the sched_entity across the tg tree to make it > >> + * visible to the root > >> + */ > >> +static void propagate_entity_cfs_rq(struct sched_entity *se) > >> +{ > >> + struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> + > >> + if (cfs_rq_throttled(cfs_rq)) > >> + return; > >> + > >> + if (!throttled_hierarchy(cfs_rq)) > >> + list_add_leaf_cfs_rq(cfs_rq); > >> + > >> + /* Start to propagate at parent */ > >> + se = se->parent; > >> + > >> + for_each_sched_entity(se) { > >> + cfs_rq = cfs_rq_of(se); > >> + > >> + update_load_avg(cfs_rq, se, UPDATE_TG); > >> + > >> + if (cfs_rq_throttled(cfs_rq)) > >> + break; > >> + > >> + if (!throttled_hierarchy(cfs_rq)) > >> + list_add_leaf_cfs_rq(cfs_rq); > >> + } > >> +} > >> +#else > >> +static void propagate_entity_cfs_rq(struct sched_entity *se) { } > >> +#endif > >> + > >> +static void detach_entity_cfs_rq(struct sched_entity *se) > >> +{ > >> + struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> + > >> + /* > >> + * In case the task sched_avg hasn't been attached: > >> + * - A forked task which hasn't been woken up by wake_up_new_task(). > >> + * - A task which has been woken up by try_to_wake_up() but is > >> + * waiting for actually being woken up by sched_ttwu_pending(). > >> + */ > >> + if (!se->avg.last_update_time) > >> + return; > > > > The 2 lines above and the associated comment are the only relevant > > part of the patch, aren't they ? > > Is everything else just code moving from one place to another one > > without change ? > > Yes, everything else is just code movement.
Could you remove such code movement ? It doesn't add any value to the patch, does it ? But It makes the patch quite difficult to review and I wasted a lot of time looking for what really changed in the code
Thanks
> > Thanks! > > > > >> + > >> + /* Catch up with the cfs_rq and remove our load when we leave */ > >> + update_load_avg(cfs_rq, se, 0); > >> + detach_entity_load_avg(cfs_rq, se); > >> + update_tg_load_avg(cfs_rq); > >> + propagate_entity_cfs_rq(se); > >> +} > >> + > >> +static void attach_entity_cfs_rq(struct sched_entity *se) > >> +{ > >> + struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> + > >> + /* Synchronize entity with its cfs_rq */ > >> + update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD); > >> + attach_entity_load_avg(cfs_rq, se); > >> + update_tg_load_avg(cfs_rq); > >> + propagate_entity_cfs_rq(se); > >> +} > >> + > >> static inline unsigned long cfs_rq_runnable_avg(struct cfs_rq *cfs_rq) > >> { > >> return cfs_rq->avg.runnable_avg; > >> @@ -4308,11 +4371,8 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s > >> } > >> > >> static inline void remove_entity_load_avg(struct sched_entity *se) {} > >> - > >> -static inline void > >> -attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} > >> -static inline void > >> -detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} > >> +static inline void detach_entity_cfs_rq(struct sched_entity *se) {} > >> +static inline void attach_entity_cfs_rq(struct sched_entity *se) {} > >> > >> static inline int newidle_balance(struct rq *rq, struct rq_flags *rf) > >> { > >> @@ -11519,62 +11579,6 @@ static inline bool vruntime_normalized(struct task_struct *p) > >> return false; > >> } > >> > >> -#ifdef CONFIG_FAIR_GROUP_SCHED > >> -/* > >> - * Propagate the changes of the sched_entity across the tg tree to make it > >> - * visible to the root > >> - */ > >> -static void propagate_entity_cfs_rq(struct sched_entity *se) > >> -{ > >> - struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> - > >> - if (cfs_rq_throttled(cfs_rq)) > >> - return; > >> - > >> - if (!throttled_hierarchy(cfs_rq)) > >> - list_add_leaf_cfs_rq(cfs_rq); > >> - > >> - /* Start to propagate at parent */ > >> - se = se->parent; > >> - > >> - for_each_sched_entity(se) { > >> - cfs_rq = cfs_rq_of(se); > >> - > >> - update_load_avg(cfs_rq, se, UPDATE_TG); > >> - > >> - if (cfs_rq_throttled(cfs_rq)) > >> - break; > >> - > >> - if (!throttled_hierarchy(cfs_rq)) > >> - list_add_leaf_cfs_rq(cfs_rq); > >> - } > >> -} > >> -#else > >> -static void propagate_entity_cfs_rq(struct sched_entity *se) { } > >> -#endif > >> - > >> -static void detach_entity_cfs_rq(struct sched_entity *se) > >> -{ > >> - struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> - > >> - /* Catch up with the cfs_rq and remove our load when we leave */ > >> - update_load_avg(cfs_rq, se, 0); > >> - detach_entity_load_avg(cfs_rq, se); > >> - update_tg_load_avg(cfs_rq); > >> - propagate_entity_cfs_rq(se); > >> -} > >> - > >> -static void attach_entity_cfs_rq(struct sched_entity *se) > >> -{ > >> - struct cfs_rq *cfs_rq = cfs_rq_of(se); > >> - > >> - /* Synchronize entity with its cfs_rq */ > >> - update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD); > >> - attach_entity_load_avg(cfs_rq, se); > >> - update_tg_load_avg(cfs_rq); > >> - propagate_entity_cfs_rq(se); > >> -} > >> - > >> static void detach_task_cfs_rq(struct task_struct *p) > >> { > >> struct sched_entity *se = &p->se; > >> -- > >> 2.36.1 > >>
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