Hello, Prateek. On Fri, Dec 08, 2017 at 05:15:55PM +0530, Prateek Sood wrote: > There is one deadlock issue during cgroup migration from cpu > hotplug path when a task T is being moved from source to > destination cgroup. > > kworker/0:0 > cpuset_hotplug_workfn() > cpuset_hotplug_update_tasks() > hotplug_update_tasks_legacy() > remove_tasks_in_empty_cpuset() > cgroup_transfer_tasks() // stuck in iterator loop > cgroup_migrate() > cgroup_migrate_add_task() > > In cgroup_migrate_add_task() it checks for PF_EXITING flag of task T. > Task T will not migrate to destination cgroup. css_task_iter_start() > will keep pointing to task T in loop waiting for task T cg_list node > to be removed.
Heh, that's a bug in cgroup_transfer_tasks() which happened because I forgot to update when we changed how we handle exiting tasks. The right thing to do here is making cgroup_transfer_tasks() repeat iff there were a valid migration target which didn't get transferred. Thanks. -- tejun
