Messages in this thread Patch in this message | | | Date | Thu, 25 Apr 2019 10:26:53 -0400 | From | Phil Auld <> | Subject | Re: [RFC PATCH v2 12/17] sched: A quick and dirty cgroup tagging interface |
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On Tue, Apr 23, 2019 at 04:18:17PM +0000 Vineeth Remanan Pillai wrote: > From: Peter Zijlstra (Intel) <peterz@infradead.org> > > Marks all tasks in a cgroup as matching for core-scheduling. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/sched/core.c | 62 ++++++++++++++++++++++++++++++++++++++++++++ > kernel/sched/sched.h | 4 +++ > 2 files changed, 66 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 5066a1493acf..e5bdc1c4d8d7 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6658,6 +6658,15 @@ static void sched_change_group(struct task_struct *tsk, int type) > tg = container_of(task_css_check(tsk, cpu_cgrp_id, true), > struct task_group, css); > tg = autogroup_task_group(tsk, tg); > + > +#ifdef CONFIG_SCHED_CORE > + if ((unsigned long)tsk->sched_task_group == tsk->core_cookie) > + tsk->core_cookie = 0UL; > + > + if (tg->tagged /* && !tsk->core_cookie ? */) > + tsk->core_cookie = (unsigned long)tg; > +#endif > + > tsk->sched_task_group = tg; > > #ifdef CONFIG_FAIR_GROUP_SCHED > @@ -7117,6 +7126,43 @@ static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css, > } > #endif /* CONFIG_RT_GROUP_SCHED */ > > +#ifdef CONFIG_SCHED_CORE > +static u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) > +{ > + struct task_group *tg = css_tg(css); > + > + return !!tg->tagged; > +} > + > +static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype *cft, u64 val) > +{ > + struct task_group *tg = css_tg(css); > + struct css_task_iter it; > + struct task_struct *p; > + > + if (val > 1) > + return -ERANGE; > + > + if (tg->tagged == !!val) > + return 0; > + > + tg->tagged = !!val; > + > + if (!!val) > + sched_core_get(); > + > + css_task_iter_start(css, 0, &it); > + while ((p = css_task_iter_next(&it))) > + p->core_cookie = !!val ? (unsigned long)tg : 0UL; > + css_task_iter_end(&it); > + > + if (!val) > + sched_core_put(); > + > + return 0; > +} > +#endif > + > static struct cftype cpu_legacy_files[] = { > #ifdef CONFIG_FAIR_GROUP_SCHED > { > @@ -7152,6 +7198,14 @@ static struct cftype cpu_legacy_files[] = { > .read_u64 = cpu_rt_period_read_uint, > .write_u64 = cpu_rt_period_write_uint, > }, > +#endif > +#ifdef CONFIG_SCHED_CORE > + { > + .name = "tag", > + .flags = CFTYPE_NOT_ON_ROOT, > + .read_u64 = cpu_core_tag_read_u64, > + .write_u64 = cpu_core_tag_write_u64, > + }, > #endif > { } /* Terminate */ > }; > @@ -7319,6 +7373,14 @@ static struct cftype cpu_files[] = { > .seq_show = cpu_max_show, > .write = cpu_max_write, > }, > +#endif > +#ifdef CONFIG_SCHED_CORE > + { > + .name = "tag", > + .flags = CFTYPE_NOT_ON_ROOT, > + .read_u64 = cpu_core_tag_read_u64, > + .write_u64 = cpu_core_tag_write_u64, > + }, > #endif > { } /* terminate */ > }; > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 42dd620797d7..16fb236eab7b 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -363,6 +363,10 @@ struct cfs_bandwidth { > struct task_group { > struct cgroup_subsys_state css; > > +#ifdef CONFIG_SCHED_CORE > + int tagged; > +#endif > + > #ifdef CONFIG_FAIR_GROUP_SCHED > /* schedulable entities of this group on each CPU */ > struct sched_entity **se; > -- > 2.17.1 >
Since CPU0 never goes through the cpu add code it will never get initialized if it's the only cpu and then enabling core scheduling and adding a task crashes.
Since there is no point in using core sched in this case maybe just disallow it with something the below?
Cheers, Phil
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e8e5f26db052..b312ea1e28a4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7541,6 +7541,9 @@ static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype if (val > 1) return -ERANGE; + if (num_online_cpus() <= 1) + return -EINVAL; + if (tg->tagged == !!val) return 0;
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