| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <43a53d86-0a8c-6736-424a-a45dc014e8c4@bytedance.com>
Date: Wed, 17 Aug 2022 23:10:31 +0800
From: Chengming Zhou <zhouchengming@...edance.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
vschneid@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/9] sched/fair: fix another detach on unattached task
corner case
On 2022/8/17 23:08, Vincent Guittot wrote:
> On Wed, 17 Aug 2022 at 17:04, Chengming Zhou
> <zhouchengming@...edance.com> wrote:
>>
>> On 2022/8/17 23:01, Vincent Guittot wrote:
>>> On Mon, 8 Aug 2022 at 14:58, Chengming Zhou <zhouchengming@...edance.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@...edance.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
>
Sorry about that. No problem, I will remove it.
Thanks!
> 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
>>>>
Powered by blists - more mailing lists