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Tue, 11 Aug 2026 14:43:15 +0000 (GMT) Received: from osiris (unknown [9.87.143.60]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 11 Aug 2026 14:43:15 +0000 (GMT) Date: Tue, 11 Aug 2026 16:43:14 +0200 From: Heiko Carstens To: Thomas Richter Cc: linux-s390@vger.kernel.org, sumanthk@linux.ibm.com, japo@linux.ibm.com, agordeev@linux.ibm.com, iii@linux.ibm.com, Christian Borntraeger , Vasily Gorbik Subject: Re: [PATCH v3] s390/cpum_cf: Handle CPU hotplug via prepare/dead callbacks Message-ID: <20260811144314.12308Eea-hca@linux.ibm.com> References: <20260811133901.3765063-1-tmricht@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260811133901.3765063-1-tmricht@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDEyMSBTYWx0ZWRfX/OEOYHLZ2UZg wojukBBrH6jEg8HX5XvVtVi5mCeA6mGeX/JleY/Wzl0+oUb4djrIblgYcr8n0xipAWsV/04Q9Cg b6NRfMfinxCLUsnPDGyf4miDV3LZ+RJ0h4JDcU6R5amEyUBOR5zmaEIGhwxm/rDjx+YNA4Mw8c1 mDN71X9zieZBBMosqXhnyVWe8fRx+Dzem9lAkJMXLfSDWTnGb1h7jBNZkItjbYO4FsrUeLpwtDd HNx5z13e8MNeyc7em2Dy7DVDTEl5suAcg3ctTGeLqL0+fnFNUese2fvY7IN5gm3PAwdRCjvdXhx F//pqOdib+ygKrWCF+O6NbNjVT9piYYSnmzOWoN3d2qRndta/2dKF3ddN34vMdEv3NptRmSkQ/L Ga+u8VFuBTyhnI9TqdnqsksN4i/z/g3r6sJuwQ+fL1/jxIj5Zu1zb65WsyAh1sJ5C/Tvbh4TtXx ww14PFn7JXVsNMOBYvQ== X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDEyMSBTYWx0ZWRfX2KLYTA2Zgpiu IXOwrW0pqvmz5ee/ImDjNT2eToStagQaEiFB4mGCSR0wt2MNOErxtKtcg4goGL8I7p8BwLXJ2kx GjdadXIIGgX9hKWcJIzar0nZza9tzA0= X-Authority-Analysis: v=2.4 cv=RqD16imK c=1 sm=1 tr=0 ts=6a7b3509 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=SVoRsXcwFpO9loE_4oYA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: L7cJTXfRZkrfY-te-m-fM86gSwlUI2_I X-Proofpoint-ORIG-GUID: L7cJTXfRZkrfY-te-m-fM86gSwlUI2_I 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=2026-08-11_03,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 lowpriorityscore=0 clxscore=1015 adultscore=0 bulkscore=0 malwarescore=0 impostorscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110121 On Tue, Aug 11, 2026 at 03:39:01PM +0200, Thomas Richter wrote: > The command 'perf stat -e cycles -- ' crashes the kernel > when CPUs are hotplug added during that run. ... > Fixes: 9b9cf3c77e7e ("s390/cpum_cf: rework PER_CPU_DEFINE of struct cpu_cf_events") > Cc: # v6.5+ > Signed-off-by: Thomas Richter > Suggested-by: Heiko Carstens > Suggested-by: Christian Borntraeger > --- > arch/s390/kernel/perf_cpum_cf.c | 215 +++++++++++++++++++++----------- > 1 file changed, 142 insertions(+), 73 deletions(-) ... > @@ -167,12 +170,14 @@ static void cpum_cf_reset_cpu(void *flags) > } > > /* Free per CPU data when the last event is removed. */ > -static void cpum_cf_free_root(void) > +static void cpum_cf_free_root(unsigned int num) > { > - if (!refcount_dec_and_test(&cpu_cf_root.refcnt)) > + struct cpu_cf_ptr __percpu *p = cpu_cf_root.cfptr; > + > + if (!refcount_sub_and_test(num, &cpu_cf_root.refcnt)) > return; > - free_percpu(cpu_cf_root.cfptr); > cpu_cf_root.cfptr = NULL; > + free_percpu(p); This appears to be an unrelated fix. But anyway: Acked-by: Heiko Carstens