From: Waiman Long longman@redhat.com
commit 2bdfd2825c9662463371e6691b1a794e97fa36b4 upstream.
It was found that a "suspicious RCU usage" lockdep warning was issued with the rcu_read_lock() call in update_sibling_cpumasks(). It is because the update_cpumasks_hier() function may sleep. So we have to release the RCU lock, call update_cpumasks_hier() and reacquire it afterward.
Also add a percpu_rwsem_assert_held() in update_sibling_cpumasks() instead of stating that in the comment.
Fixes: 4716909cc5c5 ("cpuset: Track cpusets that use parent's effective_cpus") Signed-off-by: Waiman Long longman@redhat.com Tested-by: Phil Auld pauld@redhat.com Reviewed-by: Phil Auld pauld@redhat.com Signed-off-by: Tejun Heo tj@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/cgroup/cpuset.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1481,10 +1481,15 @@ static void update_sibling_cpumasks(stru struct cpuset *sibling; struct cgroup_subsys_state *pos_css;
+ percpu_rwsem_assert_held(&cpuset_rwsem); + /* * Check all its siblings and call update_cpumasks_hier() * if their use_parent_ecpus flag is set in order for them * to use the right effective_cpus value. + * + * The update_cpumasks_hier() function may sleep. So we have to + * release the RCU read lock before calling it. */ rcu_read_lock(); cpuset_for_each_child(sibling, pos_css, parent) { @@ -1492,8 +1497,13 @@ static void update_sibling_cpumasks(stru continue; if (!sibling->use_parent_ecpus) continue; + if (!css_tryget_online(&sibling->css)) + continue;
+ rcu_read_unlock(); update_cpumasks_hier(sibling, tmp); + rcu_read_lock(); + css_put(&sibling->css); } rcu_read_unlock(); }