Messages in this thread | | | Date | Mon, 11 Jul 2022 21:02:07 +0800 | Subject | Re: [External] Re: [PATCH 3/8] sched/fair: remove redundant cpu_cgrp_subsys->fork() | From | Chengming Zhou <> |
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On 2022/7/11 15:35, Peter Zijlstra wrote: > On Sat, Jul 09, 2022 at 11:13:48PM +0800, Chengming Zhou wrote: >> We use cpu_cgrp_subsys->fork() to set task group for the new fair task >> in cgroup_post_fork(). >> >> Since commit b1e8206582f9 ("sched: Fix yet more sched_fork() races") >> has already set task group for the new fair task in sched_cgroup_fork(), >> so cpu_cgrp_subsys->fork() can be removed. >> >> cgroup_can_fork() --> pin parent's sched_task_group >> sched_cgroup_fork() >> __set_task_cpu --> set task group >> cgroup_post_fork() >> ss->fork() := cpu_cgroup_fork() --> set again >> >> After this patch's change, task_change_group_fair() only need to >> care about task cgroup migration, make the code much simplier. > > This: > >> This patch also move the task se depth setting to set_task_rq(), which >> will set correct depth for the new task se in sched_cgroup_fork(). >> >> The se depth setting in attach_entity_cfs_rq() is removed since >> set_task_rq() is a better place to do this when task moves across >> CPUs/groups. > > really should have been it's own patch. And this actually scares me. Did > you test with priority inheritance bumping the task to FIFO while things > change? > > This has nothing to do with fork().
Ok, will put this in another patch, so this patch still need this line:
p->se.depth = tg->se[cpu] ? tg->se[cpu]->depth + 1 : 0;
in set_task_rq() to set depth for new forked task.
I didn't test with "priority inheritance bumping the task to FIFO" case, do you mean the rt_mutex_setprio() bump a fair task to FIFO?
Sorry, I don't get how removing depth setting in attach_entity_cfs_rq() affect that. Could you explain more so I can test it?
Thanks.
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