From: Tejun Heo <tj@kernel.org>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: lizefan@huawei.com, mingo@redhat.com, peterz@infradead.org,
richard@nod.at, "Frédéric Weisbecker" <fweisbec@gmail.com>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [PATCH v10 3/4] cgroups: allow a cgroup subsystem to reject a fork
Date: Fri, 24 Apr 2015 11:48:30 -0400 [thread overview]
Message-ID: <20150424154830.GD24029@htj.duckdns.org> (raw)
In-Reply-To: <CAOviyajrizKYCbSZZU0BzYeH_8A62_vq1zyzJ-z7=qBV+owWSg@mail.gmail.com>
On Fri, Apr 24, 2015 at 11:59:31PM +1000, Aleksa Sarai wrote:
> Hey,
>
> >> +#define CGROUP_PREFORK_COUNT 0
> >> +
> >> static inline int cgroup_init_early(void) { return 0; }
> >> static inline int cgroup_init(void) { return 0; }
> >> static inline void cgroup_fork(struct task_struct *p) {}
> >> -static inline void cgroup_post_fork(struct task_struct *p) {}
> >> +static inline int cgroup_can_fork(struct task_struct *p,
> >> + void *s[CGROUP_PREFORK_COUNT])
> >> +{
> >> + return 0;
> >> +}
> >
> > Style consistency?
>
> It's because it wraps. I can move it to be something like:
>
> static inline int cgroup_can_fork(struct task_struct *p,
> void *s[CGROUP_PREFORK_COUNT])
> { return 0; }
static inline int cgroup_can_fork(struct task_struct *p,
void *s[CGROUP_PREFORK_COUNT])
{ return 0; }
> >> @@ -2078,6 +2084,18 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
> >> list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
> >>
> >> /*
> >> + * We detach from the old_cset subsystems here. We must do this
> >> + * before we drop the refcount for old_cset, in order to make sure
> >> + * that nobody frees it underneath us.
> >> + */
> >> + for_each_e_css(css, i, old_cgrp) {
> >> + struct cgroup_subsys_state *old_css = old_cset->subsys[i];
> >> +
> >> + if (old_css->ss->detach)
> >> + old_css->ss->detach(old_css, tsk);
> >> + }
> >
> > I don't get this. What can ->detach do that ->can_attach cannot?
>
> ->detach signifies that a task is being migrated away from a cgroup.
> On second thought, we could just use task_css() on each task in the
> tset to figure out what the cgroup the task is being migrated away
> from is and just uncharge that inside ->can_attach.
Yeah, that's how it's supposed to be used. You have access to both
pre and post csses before migration and only to the new ones once by
the time ->attach() is running.
> On the same point, are all the tasks in a tset passed to ->can_attach
> guaranteed to have the same css? Or do I have to uncharge each one
> individually?
They're the same.
Thanks.
--
tejun
next prev parent reply other threads:[~2015-04-24 15:48 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-19 12:22 [PATCH v10 0/4] cgroups: add pids subsystem Aleksa Sarai
2015-04-19 12:22 ` [PATCH v10 1/4] cgroups: use bitmask to filter for_each_subsys Aleksa Sarai
2015-04-22 15:25 ` Tejun Heo
2015-04-22 15:42 ` Peter Zijlstra
2015-04-22 16:02 ` Tejun Heo
2015-04-26 16:05 ` Aleksa Sarai
2015-04-26 16:09 ` Tejun Heo
2015-05-13 5:44 ` Aleksa Sarai
2015-05-13 13:50 ` Tejun Heo
2015-04-22 15:30 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 2/4] cgroups: replace explicit ss_mask checking with for_each_subsys_which Aleksa Sarai
2015-04-22 15:31 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 3/4] cgroups: allow a cgroup subsystem to reject a fork Aleksa Sarai
2015-04-22 15:54 ` Tejun Heo
2015-04-24 13:59 ` Aleksa Sarai
2015-04-24 15:48 ` Tejun Heo [this message]
2015-05-14 10:57 ` Aleksa Sarai
2015-05-14 15:08 ` Tejun Heo
2015-04-19 12:22 ` [PATCH v10 4/4] cgroups: implement the PIDs subsystem Aleksa Sarai
2015-04-22 16:29 ` Tejun Heo
2015-04-23 0:43 ` Aleksa Sarai
2015-04-24 15:36 ` Tejun Heo
2015-05-13 17:04 ` Aleksa Sarai
2015-05-13 17:29 ` Tejun Heo
2015-05-13 17:44 ` Aleksa Sarai
2015-05-13 17:47 ` Tejun Heo
2015-05-16 3:59 ` Aleksa Sarai
2015-05-18 1:24 ` Tejun Heo
2015-04-24 14:24 ` Aleksa Sarai
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