[LTP] [PATCH] cgroup_regression_test: Use unique names for hierarchies in each test

[Andrea Cervesato]

On 7/11/25 2:08 PM, Michal Koutný wrote:
> On Fri, Jul 11, 2025 at 12:36:15PM +0200, Andrea Cervesato <andrea.cervesato@suse.com> wrote:
>> On 7/10/25 11:00 AM, Cyril Hrubis wrote:
> ...
>>> This indeed looks like a workaround for a bug either in the test or in
>>> the system.
>>>
>> Perhaps, by placing sync before every new test which is going to mount a new
>> cgroup folder we fix the issue as well.
> That may only a workaround too. My bet is you'd rather need some RCU
> barriers or workqueue flushing, thus the simple separation by name. The
> cleanup path is just so asynchronous (the code had already attempted
> some nastiness [1], however, I'm suspecting its efficiency may be
> reduced under layers of VFS reworks since then).
>
>> I'm wondering if we should dig into it a big deeper...
> It may be worth checking that there's a change in util-linux that has
> (presumably) affected timings.
> Note that unmounting a cgroup hierarchy is operation that typically
> happens once during "lifetime" (if at all) -- so it's your call.
I see, thanks for the suggestion. I will take a look.
>
> HTH,
> Michal
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=970317aa48c6ef66cd023c039c2650c897bad927

This git commit is part of cgroup v1 code and now in 
kernel/cgroup/cgroup-v1.c:cgroup1_root_to_use, but I don't see the same 
mechanism used by cgroup v2, which is our main version. Is that 
something which might affect our system?

- Andrea