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regressions@lists.linux.dev, stable@vger.kernel.org, linux-rt-users@vger.kernel.org Date: Mon, 11 May 2026 07:50:10 +0200 In-Reply-To: <04657838-46d1-432d-95e1-eb73b930b032@mailbox.org> References: <04657838-46d1-432d-95e1-eb73b930b032@mailbox.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Provags-ID: V03:K1:UJsqE6cITQCeGD1xwNumGYt+t2NS3uQ/NbVTwASzZryTUjawul5 1nQvKGt4R4cpMqtcQ7KTj2382cQ9ISLX2rimmbYqNYgxqSSRy5S9oI3z/cmeUlNSugY4Xn8 bH0YkoI/ab6UUYYxTF3uXD1zbp8H2Tgd5W40yEsfk/diSxg2K5snN7fQ9zoC3CcHjHnc30i rqE26JWyYw4+9fbjppO4g== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:JrAeleBm9ng=;lwLr2GBZDtlzaRvptRmxpsPUING RbyHzOH3gdOwHsonEcJ+jWgAqitjmWWJkhpV83XVZC4/CWm+GI4jZs241GQqHuOaYzOm+rEc/ 2XOfi4IwgY7HIAAFPQaOcTFXYJ6Zo3VJzJseH9aCdJsUJtmFhpr8HyQwYOcZy16LEuLyBwnHy 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AebfgocnmMrBAwlHdzxCspdeau511lBIKkMrTywb/UDxkFBCQFpM6nQVuOzX50qKDNz46Nadl aaz7Y1D6Xuo2yVzGiwV1UQRz7nqicsHOc5LCLsoFgkW2Q2mexyRmA4Chqe3DmX/NjovVI1/iB 6W00Utp3gb3naoT3IxoRe20SPiChH+pdi1HBM033knL+Ls4+5IT3G7udo+KQ27FGKS4dGfAzR ZVGM47B6LtS11xKXEfqbsKz2Gi2CsrykN+S0ItwaAhWwFYJXfNl83nKLeCiXqg6B+r7KDZ246 b5pwNZzRHtmzCuG368ZxVENtmT6HCRorA1Ib1TJo9bSCxU2r8IWg9Hi1Di1MhAS5XPLmtgCbm FDdKB9ctRn96FgiarUSrGG7fgjLDAMrns+BCLjws006iMJS/ggCpEyFSs41G0s4oOB1CFkKFa ZmXYs/mDtdvceuWM6j2VXdZF7XI3BlI1U5r1/LNOdbMDmuLDHZQP2HDGRCa7EE6miCy2KaZj2 MVqK6EX3ulEyuWFbZ7SFBEcrpQv/B2W8+myf3Ci3CWrlKwLNLLZ4M6qmmG4Whfio9a5+sxAK7 8DTZ+hyBB8t51BjfHxGfYiMCR9mv85Y35Bk3ZjrHUw9P+ZFHXX3HIGPVkqRTM8AztkkwYQkDR lzkkLGQhzyNe+vSKNYFVyn4/GGJ06PH7Pcw0= On Sun, 2026-05-10 at 22:57 +0200, Lukas Beckmann wrote: > Hi, Greetings! > I am reporting a regression which was introduced by d66792919d4f on 6.12.= y. > Since this commit, cyclictest reports latencies up to 50 milliseconds,= =20 > on kernels with CONFIG_PREEMPT_RT=3Dy. >=20 > Steps to reproduce: > 1. run a load (e.g. stress-ng --cpu 4 --io 2 --vm 2 --vm-bytes 128M) > 2. run cyclictest (e.g. cyclictest -a -t -m -p 80 -i 250 -d 0) ... > I found this, because Debian updated its rt kernel from 6.12.74 to 6.12.8= 5. > The issue was also present with upstream 6.12.85 and HEAD, but not with= =20 > 6.12.74, so I started bisecting and eventually found d66792919d4f. >=20 > Is it possible to revert the commit? >=20 > I can provide traces or help wth testing if needed. FWIW, my box says this *may* be due to a fix (+follow-ups) that didn't wander back to stable. cccb45d7c429 ("sched/deadline: Less agressive dl_server handling") Fixes: 557a6bfc662c ("sched/fair: Add trivial fair server") Follow-ups: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck") a3a70caf7906 ("sched/deadline: Fix dl_server behaviour") Local 6.12-rt tree containing the above (et al) failed to reproduce in the hour I let it try to, whereas a build excluding only all locally added fix backports reproduced in fairly short order. Suspects NOT confirmed in total isolation... -Mike