> }
> prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
> - if (!cgroup_clear_css_refs(cgrp)) {
> - mutex_unlock(&cgroup_mutex);
> - /*
> - * Because someone may call cgroup_wakeup_rmdir_waiter() before
> - * prepare_to_wait(), we need to check this flag.
> - */
> - if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
> - schedule();
> - finish_wait(&cgroup_rmdir_waitq, &wait);
> - clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
> - if (signal_pending(current))
> - return -EINTR;
> - goto again;
> +
> + local_irq_disable();
> +
> + /* block new css_tryget() by deactivating refcnt */
> + for_each_subsys(cgrp->root, ss) {
> + struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
> +
> + WARN_ON(atomic_read(&css->refcnt) < 0);
> + atomic_add(CSS_DEACT_BIAS, &css->refcnt);
> }
> - /* NO css_tryget() can success after here. */
> +
> + /*
> + * Set REMOVED. All in-progress css_tryget() will be released.
> + * Put all the base refs. Each css holds an extra reference to the
> + * cgroup's dentry and cgroup removal proceeds regardless of css
> + * refs. On the last put of each css, whenever that may be, the
> + * extra dentry ref is put so that dentry destruction happens only
> + * after all css's are released.
> + */
> + for_each_subsys(cgrp->root, ss) {
> + struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
> +
> + set_bit(CSS_REMOVED, &css->flags);
> + css_put(css);
> + }
> +
> + local_irq_enable();
> +
> finish_wait(&cgroup_rmdir_waitq, &wait);
It seems to me that the main reason for doing this in two passes was to
derive a global "failed" state on the first pass. Now that we can't
fail, why can't you just loop through the subsystems just once ?
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