linux-kernel - Re: [PATCH v10 6/9] kselftests: cgroup: add freezer controller self-tests

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Date:   Wed, 17 Jul 2019 00:49:09 +0000
From:   Roman Gushchin <guro@...com>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
CC:     Roman Gushchin <guroan@...il.com>, Tejun Heo <tj@...nel.org>,
        "Oleg Nesterov" <oleg@...hat.com>,
        Kernel Team <Kernel-team@...com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Shuah Khan <shuah@...nel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "lkft-triage@...ts.linaro.org" <lkft-triage@...ts.linaro.org>
Subject: Re: [PATCH v10 6/9] kselftests: cgroup: add freezer controller
 self-tests

On Tue, Jul 16, 2019 at 08:18:39PM +0530, Naresh Kamboju wrote:
> Hi Roman,
> 
> Just want to share information here on what we notice on running this test case,

Hi Naresh!

Thank you for the report!

The interaction between ptrace and freezer is complicated
(as ptrace in general),so there are known cases when spurious
cgroup transitions (frozen <-> non frozen <-> frozen ) can happen.

Does it create any difficulties? If so, I'll send a diff to ignore
the result of this test for now.

Thank you!

> 
> On Fri, 5 Apr 2019 at 23:17, Roman Gushchin <guroan@...il.com> wrote:
> >
> > This patch implements 9 tests for the freezer controller for
> > cgroup v2:
> ...
> > 6) ptrace test: the test checks that it's possible to attach to
> > a process in a frozen cgroup, get some information and detach, and
> > the cgroup will remain frozen.
> 
> selftests cgroup test_freezer failed because of the sys entry path not found.

Can you, please, elaborate on this?

>  Cgroup /sys/fs/cgroup/unified/cg_test_ptrace isn't frozen
> /sys/fs/cgroup/unified/cg_test_ptrace: isn't_frozen #
> # not ok 6 test_cgfreezer_ptrace
> 
> This test case fails intermittently.

Thank you!