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Mon, 8 Jun 2026 16:11:13 +0000 (GMT) From: Sven Schnelle To: Heiko Carstens Cc: Alexander Gordeev , Vasily Gorbik , Christian Borntraeger , Massimiliano Pellizzer , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH] s390: Remove GENERIC_LOCKBREAK Kconfig option In-Reply-To: <20260605153206.2397521-1-hca@linux.ibm.com> References: <20260605153206.2397521-1-hca@linux.ibm.com> Date: Mon, 08 Jun 2026 18:11:05 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=HppG3UTS c=1 sm=1 tr=0 ts=6a26e9a6 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=DfNHnWVPAAAA:8 a=otxGPKif3PPhFqwVwwAA:9 a=rjTVMONInIDnV1a_A2c_:22 X-Proofpoint-GUID: M_JFT91W1Xzo7FlsQk-vTceUo04n7BP2 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA4MDE1MyBTYWx0ZWRfX/IulBOrD5/Mu zyBU3rklXHN3JVbBkbpkDt5CwdHaJX8n2k9a8+PNclNJ5L95GwTExRZcMSY0nQ+YtTyG6F0rQtb bldHkbfBuccongR0u8XOaWigx+UzhXByRfiBKTWnJoTYSQESTPRahci+BZVwYbvQ52WoGi67Rje 3vSp5/SVfRqv+WlPvfxI1rV8rYh+U6GA8r+OnEZyIlEOiznDKyrlljXaEUzmdSrR8QvwqZCnXuR lqcSYC++9iKGUz2+rWdb1Z5EEpKPngO1Kq5xs50UrWi7oFK2hZHhr+B3HtLo/QdjmHK9WzEG+Hm 3k8mf2KjWCdjTbq0p++sZaQDGyU82CMNtE377BjKR8YM5idLsUQ1gTU4jaUs3Pj6E0Pb7lycyRl RvuYoESuaXijxiFO9upnYHlsAf7RNAEUWISxanQF+k1+ELCAiLzwXZJ+G6ZAQXs2J0Fq4DXUsMU UtTFK3n1HTmo/xp2eZg== X-Proofpoint-ORIG-GUID: M_JFT91W1Xzo7FlsQk-vTceUo04n7BP2 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=2026-06-08_04,2026-06-05_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 clxscore=1011 bulkscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606080153 Heiko Carstens writes: > 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 > > -config GENERIC_LOCKBREAK > - def_bool y if PREEMPTION > - > config AUDIT_ARCH > def_bool y Reviewed-by: Sven Schnelle