Messages in this thread | | | From | Kirill Tkhai <> | Subject | Re: [PATCH] sched: reset sched_entity depth on changing parent | Date | Mon, 27 Oct 2014 16:36:02 +0300 |
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27.10.2014, 16:28, "Peter Zijlstra" <peterz@infradead.org>: > On Mon, Oct 27, 2014 at 08:40:02AM -0400, Tejun Heo wrote: >> On Mon, Oct 27, 2014 at 01:07:34PM +0100, Peter Zijlstra wrote: >>> On Fri, Oct 24, 2014 at 09:18:42PM +0400, Kirill Tkhai wrote: >>>> I was seeking a places where task_group of a task may change. I can't understand >>>> how changing of parent's cgroup during fork() applies to a child. >>> I didn't know we could change cgroup on fork(), I though the idea was >>> you always inherited your parents cgroup. >>> >>> How can this be? >> Hmmm? -ENEEDMORECONTEXT but the inheriting happens at one point during >> fork in cgroup_post_fork(). The child inherits whatever the parent >> cgroup is at that point. > > So Kirill is saying that there is a race between fork and attach such > that a child can end up in a different cgroup than the parent and we > need to use the cgroup_subsys::fork call to fix that up.
I mean cgroup is the same, but sched_task_group is other (sched_task_group is equal to parent's on the moment of dup_task_struct()).
> I was always under the impression that fork was an 'atomic' operation > from the point of cgroups, an attach (or move) would happen either > before the fork or after, not during. But I appear to be mistaken in > that assumption, going by the comments around cgroup_post_fork(). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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