Commit 103a197c ("security/device_cgroup: lock assert fails in
dev_exception_clean()") grabs devcgroup_mutex to fix assert failure, but
a mutex can't be grabbed in rcu callback.  Since there shouldn't be any
other references when css_free is called, mutex isn't needed for list
cleanup in devcgroup_css_free().
Signed-off-by: NJerry Snitselaar <jerry.snitselaar@oracle.com>
Acked-by: NTejun Heo <tj@kernel.org>
Acked-by: NAristeu Rozanski <aris@redhat.com>
Cc: James Morris <james.l.morris@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>