On Tue, Nov 20, 2018 at 08:36:04AM -0800, Tejun Heo wrote: > On Tue, Nov 20, 2018 at 04:33:11PM +0000, Roman Gushchin wrote: > > > If a non-frozen task is being moved into a frozen cgroup, shouldn't > > > that also trigger frozen state update? > > > > It does! Just below these lines: > > > > /* > > * If the task isn't in the desired state, force it to it. > > */ > > if (task->frozen != test_bit(CGRP_FREEZE, &dst->flags)) > > cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags)); > > But that wouldn't udpate the cgroup's frozen state and generate > notifications, right? Why? The task will be eventually trapped into cgroup_enter_frozen(), and from there cgroup_update_frozen() will be called. You are right, that notification will not be issued, because the cgroup is not changing its state (frozen->frozen). I'm not sure that it makes sense to change the cgroup state back and forth in this case. Are there any reasons I'm missing? Thanks!
