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Tue, 6 Oct 2026 11:13:18 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 6 Oct 2026 11:13:18 +0000 (GMT) From: Sumanth Korikkar To: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Ilya Leoshkevich , Christian Borntraeger , Jan Polensky , linux-s390 Cc: sumanthk@linux.ibm.com Subject: [PATCH 0/2] s390/cpum_cf: Check session cpu mask during hotplug Date: Tue, 6 Oct 2026 13:13:02 +0200 Message-ID: <20261006111304.4023017-1-sumanthk@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=TOPQ2Fla c=1 sm=1 tr=0 ts=6ac4d7d3 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=6VcFeyx0Gwr6KzQQbJQA:9 a=zgiPjhLxNE0A:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDA2MDA0NCBTYWx0ZWRfX1KK/1S6iVAg9 ZYKpC0MGpDUVC5c6e6BBpjtjKURyn/hV/gTt3SvCivosVV/CyMwj7T+vJNbBLBW1S04GZOVHkSY j1FpSgghcb6ckKwCvG4sFu3WD2tp2qH2nZxaOW47nugtI0PV5LgropGUFBN6E9GvC5a8yqKKlIL zLGUmc1i9KjJfCezyjY5KesKzl26prhYfISlGXDHU3QiNB2vHcxbaVWuZOoOZ5lHIqXwpZRqeIR //cB9+bBvByEsZPGrD2yqgWnX7yAlPS7vDhg20w820/Ct2/7oj18FzOC2P9l6leai8hS9+ISdfU Bfgk5hdQt/fmUBNWFPhhTt8vL+qyYkZSP0KwGPBfOB1V0ejZvE2shaGAxqOh3SYWreuk2pGVsbV Cdg5/jJyMu1JS/04GFC71p5dEOoxz1K5rttPWQINeS9q6b1hUhyKzCT3wTujNJvCoAjEfw/RvI9 y9n5RG3AOO+789PdPhA== X-Proofpoint-GUID: oEwhtUi0cZR8aGL8RfvdCVHqgqtsCJe8 X-Proofpoint-ORIG-GUID: oEwhtUi0cZR8aGL8RfvdCVHqgqtsCJe8 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDA2MDA0NCBTYWx0ZWRfXzMZl2YLAHT6Z IqIx1RRh0SIdAyYgLN6Vk1XYRyCYWnuvKjz/IPRAVtBuMrmQI7xM6m9MxMHb7OEsF+Mxo7+EK2A 1IejmvtHt39eFl2xzsQEL0IlHxqK0Lw= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-06_03,2026-10-05_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 spamscore=0 adultscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 bulkscore=0 phishscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610060044 The cpu hotplug callbacks start and stop counter sets for every active hwctr session without checking the session cpu mask. This causes a reference count underflow when an unrelated cpu goes offline, and silently adds cpus to a session when they come online. Patch 1 fixes the reference count underflow in cfset_offline_cpu() and is suitable for stable kernels. It does not change the online behavior, so no matching lshwc change is required. Patch 2 extends the mask check to cfset_online_cpu() and keeps the userspace provided cpu mask unchanged across hotplug events. It requires a matching lshwc change and is therefore kept separate from patch 1. Sumanth Korikkar (2): s390/cpum_cf: Check session mask before cpu offline s390/cpum_cf: Honor hwctr session cpu mask during hotplug arch/s390/kernel/perf_cpum_cf.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) -- 2.53.0