On Mon, Feb 7, 2011 at 8:10 AM, Peter Zijlstra <pet...@infradead.org> wrote:
>
> Make the ::exit method act like ::attach, it is after all very nearly
> the same thing.
The major difference between attach and exit is that the former is
only triggered in response to user cgroup-management action, whereas
the latter is triggered whenever a task exits, even if cgroups aren't
set up.
> void cgroup_exit(struct task_struct *tsk, int run_callbacks)
> {
> - int i;
> struct css_set *cg;
> + int i;
>
> - if (run_callbacks && need_forkexit_callback) {
> - /*
> - * modular subsystems can't use callbacks, so no need to lock
> - * the subsys array
> - */
> - for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
> - struct cgroup_subsys *ss = subsys[i];
> - if (ss->exit)
> - ss->exit(ss, tsk);
> - }
> - }
> + mutex_lock(&cgroup_mutex);
NACK - cgroup_mutex is way too heavy to take in the task exit path.
We'll need to find some other way to fix this if it's really needed.
task->alloc_lock is also normally a valid thing to synchronize against
cgroup moves, but I'd have to look at the exit path to see if it's
still valid there.
Paul
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