Re: [Patch v2] sysfs: add lockdep class support to s_active

Cong Wang
2010-02-05T09:34:40Z

Eric W. Biederman wrote:
> Amerigo Wang <amwang@redhat.com> writes:
>
>> Recently we met a lockdep warning from sysfs during s2ram or cpu hotplug.
>> As reported by several people, it is something like:
>
> The interesting case is the cpu hotplug is actually a problem. It isn't
> useful to get a complaint about the non-problems code paths triggered
> by pm. However my earlier review spotted a real deadlock case. Where
> in one of the sysfs attributes we iterate over the list of online cpus
> and that appeared to an attribute that removing a cpu would remove
> from sysfs...
>

You are referring this one:
http://marc.info/?l=linux-kernel&m=126474021428905&w=2
?

Hmm, yeah, I missed that the lock it is holding is not s_active, thus so
not be the case we are trying to fix here.

Thanks for pointing this out.