On 05/16/2014 11:09 AM, Tejun Heo wrote:
> 9395a4500404 ("cgroup: enable refcnting for root csses") enabled
> reference counting for root csses (cgroup_subsys_states) so that
> cgroup's self csses can be used to manage the lifetime of the
> containing cgroups.
>
> Unfortunately, this change was incorrect. During early init,
> cgrp_dfl_root self css refcnt is used. percpu_ref can't initialized
> during early init and its initialization is deferred till
> cgroup_init() time. This means that cpu was using percpu_ref which
> wasn't properly initialized. Due to the way percpu variables are laid
> out on x86, this didn't blow up immediately on x86 but ended up
> incrementing and decrementing the percpu variable at offset zero,
> whatever it may be; however, on other archs, this caused fault and
> early boot failure.
>
> As cgroup self csses for root cgroups of non-dfl hierarchies need
> working refcounting, we can't revert 9395a4500404. This patch adds
> CSS_NO_REF which explicitly inhibits reference counting on the css and
> sets it on all normal (non-self) csses and cgroup_dfl_root self css.
>
> v2: cgrp_dfl_root.self is the offending one. Set the flag on it.
>
> Signed-off-by: Tejun Heo <[email protected]>
> Reported-by: Stephen Warren <[email protected]>
> Fixes: 9395a4500404 ("cgroup: enable refcnting for root csses")
> ---
> Hello,
>
> Can you try this one instead?
Yes, this one works great, thanks.
Tested-by: Stephen Warren <[email protected]>
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