Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs
From: Michal Hocko <hidden>
Date: 2012-10-31 19:02:42
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On Wed 31-10-12 11:16:24, Tejun Heo wrote:
2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error
handling") removed the last user of __DEPRECATED_clear_css_refs. This
patch removes __DEPRECATED_clear_css_refs and mechanisms to support
it.
* Conditionals dependent on __DEPRECATED_clear_css_refs removed.
* ->pre_destroy() now can only fail if a new task is attached or child
cgroup is created while ->pre_destroy()s are being called. As the
condition is checked again after re-acquiring cgroup_mutex
afterwards, we don't need to take any immediate action on
->pre_destroy() failures. Well, this is racy because the task can exit until we reach the re-check. As the result there might still be some pages on the memcg LRUs left. As I said in the previous version, I do not see any reason why we shouldn't just return EBUSY here. I would even skip WARN_ON_ONCE because it doesn't give us any valueable information. One can trigger that easily as well. [...]
quoted hunk ↗ jump to hunk
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7981850..033bf4b 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c
[...]
quoted hunk ↗ jump to hunk
@@ -4168,11 +4075,9 @@ again: * Call pre_destroy handlers of subsys. Notify subsystems * that rmdir() request comes. */ - ret = cgroup_call_pre_destroy(cgrp); - if (ret) { - clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); - return ret; - } + for_each_subsys(cgrp->root, ss) + if (ss->pre_destroy) + WARN_ON_ONCE(ss->pre_destroy(cgrp));
for_each_subsys(cgrp->root, ss)
if (ss->pre_destroy) {
int ret = ss->pre_destroy(cgrp);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
return ret;
}mutex_lock(&cgroup_mutex); parent = cgrp->parent;
[...] -- Michal Hocko SUSE Labs