Re: [PATCH v4 0/3] Fix deadlock caused by cgroup_mutex and cpu_hotplug_lock

[Tejun Heo]

On Wed, Sep 18, 2024 at 05:44:47PM +0800, Chen Ridong wrote:
...
> >    cgroup: fix deadlock caused by cgroup_mutex and cpu_hotplug_lock
> >    workqueue: doc: Add a note saturating the system_wq is not permitted
> >    workqueue: Adjust WQ_MAX_ACTIVE from 512 to 2048
> > 
> >   Documentation/core-api/workqueue.rst | 8 ++++++--
> >   include/linux/workqueue.h            | 2 +-
> >   kernel/bpf/cgroup.c                  | 2 +-
> >   kernel/cgroup/cgroup-internal.h      | 1 +
> >   kernel/cgroup/cgroup.c               | 2 +-
> >   5 files changed, 10 insertions(+), 5 deletions(-)
> > 
> Friendly ping.

I don't know why but this series isn't in my inbox for some reason. Here are
some feedbacks after looking at the thread from lore:

- Can you create a separate workqueue for cgrp->bpf.release_work instead of
  exporting cgroup_destroy_wq? Workqueues aren't that expensive. No reason
  to share like this.

- The patch title is rather misleading. The deadlock isn't really caused
  between cgroup_mutex and cpu_hotplug_lock. They're just victims of
  system_wq concurrency depletion. Can you please update accordingly?

- Can you add a new line before the note paragraph? Also, I'd say "deadlock"
  rather than "block" to properly convey the imapct of such saturation
  events. I don't think "eg. cgroup release work" is adding much.

Thanks.

-- 
tejun