linux-kernel - Re: [PATCH 0/2] selftests/cgroup: better bound for cpu.max tests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <bhp3gwezbmseeqonh44qjauydis6wdqb7p6digf45hsssicufy@3az65qay67r5>
Date: Thu, 3 Jul 2025 10:54:06 +0200
From: Michal Koutný <mkoutny@...e.com>
To: Shashank Balaji <shashank.mahadasyam@...y.com>
Cc: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Shuah Khan <shuah@...nel.org>, cgroups@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Shinya Takumi <shinya.takumi@...y.com>
Subject: Re: [PATCH 0/2] selftests/cgroup: better bound for cpu.max tests

On Thu, Jul 03, 2025 at 10:41:17AM +0900, Shashank Balaji <shashank.mahadasyam@...y.com> wrote:
> Going with the more natural way of sticking to CPU_HOG_CLOCK_WALL, the
> second patch does calculate expected_usage_usec based on the configured
> quota, as the code comment explains. So I'm guessesing we're on the same page
> about this?

Yes, the expected_usage_usec in the 2nd patch is correct. (It'd be nicer
if the value calculated from the configured cpu.max and not typed out as
a literal that may diverge should be the cpu.max changed in the test.)

> Do you mean something like,
> 
> 	if (values_close(usage_usec, expected_usage_usec, 10))
> 			goto cleanup;
> 
> using the positive values_close() predicate. If so, I'm not sure I
> understand because if usage_usec and expected_usage_usec _are_ close,
> then we want the test to pass! We should be using the negative
> predicate.

I meant to use it the same way like test_memcontrol.c does, i.e.
values_close() <=> pass.

So codewise it boils down to (a negation, I see why the confusion):
 	if (!values_close(usage_usec, expected_usage_usec, 10))
 		goto cleanup;
	ret = KSFT_PASS;


Michal


Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)