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Fri, 5 Jun 2026 15:32:06 +0000 (GMT) From: Heiko Carstens To: Alexander Gordeev , Sven Schnelle , Vasily Gorbik , Christian Borntraeger , Massimiliano Pellizzer Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: [PATCH] s390: Remove GENERIC_LOCKBREAK Kconfig option Date: Fri, 5 Jun 2026 17:32:06 +0200 Message-ID: <20260605153206.2397521-1-hca@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ndBGU6FBmQ_qKPLWE3IIv_l4SrNpmTQ5 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA1MDE0OSBTYWx0ZWRfX/8mBBI5cu+hv Wx/BoZAG6pOXAzD6UXIe/2W4RJ+k5L3dVmLb3qkm9k1KgGUltm17ZlEs9Y7o4UQw5bjsCsh93we xUGmatXbTQlhD9WeRAhG24hnwSPaHMLIvPoysRDbVKnpOE15KjaFepXZV4IRMdE04rG+PBhF05D V9zT8FgTE1W60eaxRQq0gJs1Z9AD9+jAaOgoXH/ywQgrb3qEK43zrN030dRlHUf/LDpo5ZSDe95 pfrxbKn+U+lG7STT6wrK6XZe1rLIsRITfkQ6/JtkU0UhMxZe86VxeduFvlKE6AuEXj1QQgzn4+1 7ADYBZDlQUTW21ag3rF6akXv4tyD/XHhZfJw6nS7jxyhL4SP9pcx1aFBYVhaPfZsOM4SXlggT06 c59dCP4YQeUWCIAEasYFmI16+ZkOqCld6CB3aR7fqgxzkmCdATHwZ34kAwAmfsg7oNYANJujZJZ 9o7MxoTkMaFE2t/xgkw== X-Proofpoint-ORIG-GUID: ndBGU6FBmQ_qKPLWE3IIv_l4SrNpmTQ5 X-Authority-Analysis: v=2.4 cv=Vf3H+lp9 c=1 sm=1 tr=0 ts=6a22ebfb cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=DfNHnWVPAAAA:8 a=VnNF1IyMAAAA:8 a=ZBlrgJuq_Oy-vTlPGZwA:9 a=rjTVMONInIDnV1a_A2c_:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-05_02,2026-06-05_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 adultscore=0 bulkscore=0 impostorscore=0 phishscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1011 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606050149 Content-Type: text/plain; charset="utf-8" s390 selects GENERIC_LOCKBREAK if PREEMPT is enabled. Reason is a historic 18 years old commit [1] which fixed a compile error for PREEMPT enabled kernels. Back than only PREEMPT_NONE and PREEMPT_VOLUNTARY kernels were considered to be important for s390. PREEMPT should "just work". However, since recently PREEMPT is always enabled [2], which also causes GENERIC_LOCKBREAK to be always enabled. For some workloads this leads to massive performance degradation; e.g. a simple kernel compile on machines with many CPUs may take up to four times longer. To fix this just remove the GENERIC_LOCKBREAK from s390's Kconfig, since the compile error from 18 years ago does not exist anymore. [1] commit b6b40c532a36 ("[S390] Define GENERIC_LOCKBREAK.") [2] commit 7dadeaa6e851 ("sched: Further restrict the preemption modes") Cc: stable@vger.kernel.org Reported-by: Massimiliano Pellizzer Signed-off-by: Heiko Carstens --- arch/s390/Kconfig | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index ecbcbb781e40..9921a3772bf7 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -29,9 +29,6 @@ config GENERIC_BUG config GENERIC_BUG_RELATIVE_POINTERS def_bool y =20 -config GENERIC_LOCKBREAK - def_bool y if PREEMPTION - config AUDIT_ARCH def_bool y =20 --=20 2.53.0