Messages in this thread | | | Date | Mon, 12 Mar 2012 09:10:40 -0700 | From | Tejun Heo <> | Subject | Re: [RFC][PATCH] cgroup: fix race between fork and cgroup freezing |
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Hello,
On Mon, Mar 12, 2012 at 05:02:04PM +0800, Li Zefan wrote: > - We still need some kind of locking to syncronize fork and the traverser. > fork side is protected by tasklist_lock, while the traverser takes > css_set_lock.
Can't we do both after tasklist_lock is released under css_set_lock?
> - After linking the new task to css set list, the task is visible and thus > can be moved to another cgroup, which makes things more complicated and > the subsystem callbacks may have to acquire cgroup_mutex.
Hmmm... freezer currently doesn't allow migrating in and out of frozen cgroup and even when it does callbacks in the migration path should synchronize against freezer->lock. I *think* that should be enough and can't see why this will be simpler or more complex depending on when fork callback is called.
> - The task_counter subsystem wants to get notified before the new task > is linked, so it's able to abort the fork.
This one maybe but for this cgroup_fork_callbacks() is already too late, isn't it? We better have pre-fork callbacks instead, no?
Thanks.
-- tejun
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