Messages in this thread | | | Date | Tue, 9 Aug 2011 17:11:55 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 7/8] cgroups: Add a task counter subsystem |
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On 07/29, Frederic Weisbecker wrote: > > +static int task_counter_can_attach_task(struct cgroup *cgrp, struct cgroup *old_cgrp, > + struct task_struct *tsk) > +{ > + struct res_counter *res = cgroup_task_counter_res(cgrp); > + struct res_counter *old_res = cgroup_task_counter_res(old_cgrp); > + struct res_counter *limit_fail_at; > + > + common_ancestor = res_counter_common_ancestor(res, old_res); > + > + return res_counter_charge_until(res, common_ancestor, 1, &limit_fail_at); > +} > > ... > > +static void task_counter_attach_task(struct cgroup *cgrp, struct cgroup *old_cgrp, > + struct task_struct *tsk) > +{ > + res_counter_uncharge_until(cgroup_task_counter_res(old_cgrp), common_ancestor, 1); > +}
This doesn't look right or I missed something.
What if tsk exits in between? Afaics this can happen with both cgroup_attach_task() and cgroup_attach_proc().
Let's look at cgroup_attach_task(). Suppose that task_counter_can_attach_task() succeeds and charges the new cgrp, Then cgroup_task_migrate() returns -ESRCH. Who will uncharge the new cgrp?
cgroup_attach_proc() is different, it calls cgroup_task_migrate() after ->attach_task(). Cough.
In this case old_cgrp can be uncharged twice, no? And again, nobody will uncharge the new cgrp?
->attach_task() can be skipped if cgrp == oldcgrp... Probably this is fine, in this case can_attach_task() shouldn't actually charge.
> @@ -1295,6 +1295,10 @@ static struct task_struct *copy_process(unsigned long clone_flags, > p->group_leader = p; > INIT_LIST_HEAD(&p->thread_group); > > + retval = cgroup_task_counter_fork(p); > + if (retval) > + goto bad_fork_free_pid; > +
Well, imho this is not good. You are adding yet another cgroup hook. Why you can not reuse cgroup_fork_callbacks() ?
Yes, it returns void. Can't we chane ->fork() to return the error and make it boolean?
Better yet,
- cgroup_fork_callbacks(p); - cgroup_callbacks_done = 1; + failed_ss = cgroup_fork_callbacks(p); + if (failed_ss) + goto bad_fork_free_pid;
...
- cgroup_exit(p, cgroup_callbacks_done); + cgroup_exit(p, failed_ss);
What do you think?
Oleg.
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