Messages in this thread | | | Date | Wed, 16 Apr 2008 21:28:33 -0700 | From | "Paul Menage" <> | Subject | Re: [PATCH] cgroup: fix a race condition in manipulating tsk->cg_list |
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On Wed, Apr 16, 2008 at 9:18 PM, Paul Menage <menage@google.com> wrote: > > My only thought about the downside of this is that an exiting task > that gets stuck somewhere between setting PF_EXITING and calling > cgroup_exit() won't show up in its cgroup's tasks file, since we'll > enable cgroup links but skip it. I guess that's not a big deal. >
How about this as an alternative approach? We can take advantage of the indirection in tsk->cgroups to create an additional distinguished css_set that indicates the task has passed the point of checking tsk->cg_list:
- create a new css_set, called exit_css_set; it has the same cgroup pointer set as init_css_set.
- in cgroup_exit(), set current->cgroups to &exit_css_set rather than &init_css_set
- in cgroup_enable_task_cg_list(), ignore any task where p->cgroups == &exit_css_set
That way we're synchronizing directly with the task_lock()-protected section in cgroup_exit(), rather than with the setting of PF_EXITING at the beginning of do_exit().
Paul
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