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

[Chen Ridong]

On 2024/9/21 3:23, Tejun Heo wrote:
> 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.

Thanks, TJ, I will do that.

Best regards,
Ridong