Bug#1092103: Linux 6.12 freeze on small machine

From	GMX <ebhb010@gmx.com>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#1092103: Linux 6.12 freeze on small machine
Date	2025-01-04 16:10 +0100
Message-ID	<K1dWN-5EPn-5@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Package: linux-image-6.12.6-amd64
Version: 6.12.6-1

Found a case where cpu freeze(100% usage) will occur.

(Tested)Environment:
CPU: 1 or 2 cores.
Memory: <= 1GB

Only tested in Virtual Machine(KVM).

Procedure:
1. Start iperf3 as server on the test machine.
2. On any client machine, start a reversed(download) test to the test machine.
To trigger the case, use 4 threads and 256k block size. Higer value slightly increase the chance.
3.Wait for iperf3 to run.
(4). After a few iteration or at test end, the server will stop responding and completly locked.(no kernel panic log, console just freeze)

 From monitoring platform , the process contained the already freezed vm uses 100% cpu(50% on 2 cores). Charts show the vm linearly increase memory usage to watermark point and never freed them(Because cpu is freezed ?).

Tested on vanilla debian 6.12 and xanmod(no debian patches) 6.12, both freezed.
Tested on xanmod 6.6, no such problem.
Tested on vanilla debian 6.1, no such problem.

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Bug#1092103: Linux 6.12 freeze on small machine GMX <ebhb010@gmx.com> - 2025-01-04 16:10 +0100
  Bug#1092103: switch to important GMX <ebhb010@gmx.com> - 2025-01-04 21:20 +0100
  Bug#1092103: switch to important GMX <ebhb010@gmx.com> - 2025-01-04 21:20 +0100
  Bug#1092103: switch to important GMX <ebhb010@gmx.com> - 2025-01-04 21:40 +0100
  Processed: switch to important "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-01-04 21:40 +0100
  Processed: Re: Bug#1092103: Linux 6.12 freeze on small machine "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-05-03 07:50 +0200
  Bug#1092103: Linux 6.12 freeze on small machine Salvatore Bonaccorso <carnil@debian.org> - 2025-05-03 07:50 +0200
  Processed: Re: Bug#1092103: issue seems gone. "Debian Bug Tracking System" <owner@bugs.debian.org> - 2025-05-03 13:50 +0200
  Bug#1092103: issue seems gone. Salvatore Bonaccorso <carnil@debian.org> - 2025-05-03 13:50 +0200

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