Re: [patch V2 00/29] lockup_detector: Cure hotplug deadlocks and replace duct tape

Ingo Molnar
2017-09-14T05:27:32Z

* Don Zickus <dzickus@redhat.com> wrote:

> On Tue, Sep 12, 2017 at 09:36:54PM +0200, Thomas Gleixner wrote:
> > The lockup detector is broken is several ways:
> >
> > - It's deadlock prone vs. CPU hotplug in various ways. Some of these
> > are due to recursive cpus_read_lock() others are due to
> > cpus_read_lock() from CPU hotplug callbacks which immediately lock
> > the machine because cpus are write locked.
> >
> > - The handling of the cpu hotplug threads happens sideways to the
> > smpboot thread infrastructure, which is racy and pointless
> >
> > - The handling of the user space sysctl interface is a complete
> > trainwreck as it fiddles directly with variables which can be
> > modified or evaluated by the running watchdogs.
> >
> > - The perf event initialization is a trainwreck as it tries to create
> > perf events over and over even if perf is not functional (no
> > hardware, ....). To avoid excessive dmesg spam it contains magic
> > printk ratelimiting along with either wrong or useless messages.
> >
> > - The code structure is horrible as ifdef sections are scattered all
> > over the place which makes it unreadable
> >
> > - There is more wreckage, but see the changelogs for the ugly details.
> >
>
> Aside from the simple compile issue in patch 25. I have no issues with this
> patchset. Thanks Thomas!
>
> Reviewed-by: Don Zickus <dzickus@redhat.com>

Thanks guys! I've applied the series and will push it out after some testing.

Thanks,

Ingo