Re: [PATCH v4 0/2] cgroup: Track time in cgroup v2 freezer

[Tejun Heo <tj@kernel.org>]

On Thu, Aug 21, 2025 at 06:37:51PM -0700, Tiffany Yang wrote:
> Hello,
> 
> The cgroup v2 freezer controller is useful for freezing background
> applications so they don't contend with foreground tasks. However, this
> may disrupt any internal monitoring that the application is performing,
> as it may not be aware that it was frozen.
> 
> To illustrate, an application might implement a watchdog thread to
> monitor a high-priority task by periodically checking its state to
> ensure progress. The challenge is that the task only advances when the
> application is running, but watchdog timers are set relative to system
> time, not app time. If the app is frozen and misses the expected
> deadline, the watchdog, unaware of this pause, may kill a healthy
> process.
> 
> This series tracks the time that each cgroup spends "freezing" and
> exposes it via cgroup.stat.local. Include several basic selftests to
> demonstrate the expected behavior of this interface, including that:
>   1. Freeze time will increase while a cgroup is freezing, regardless of
>      whether it is frozen or not.
>   2. Each cgroup's freeze time is independent from the other cgroups in
>      its hierarchy.
> 
> Thanks,
> Tiffany
> 
> Signed-off-by: Tiffany Yang <ynaffit@google.com>

Applied to cgroup/for-6.18. Let's address further issues incrementally.

Thanks.

-- 
tejun