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Thu, 28 May 2026 16:44:54 +0000 (GMT) Received: from linux.ibm.com (unknown [9.126.150.29]) by smtpav06.fra02v.mail.ibm.com (Postfix) with SMTP; Thu, 28 May 2026 16:44:53 +0000 (GMT) Date: Thu, 28 May 2026 22:14:53 +0530 From: Srikar Dronamraju To: Shrikanth Hegde Cc: Venkat Rao Bagalkote , K Prateek Nayak , "Chen, Yu C" , Ritesh Harjani , Madhavan Srinivasan , "Christophe Leroy (CS GROUP)" , LKML , linuxppc-dev , Peter Zijlstra , tim.c.chen@linux.intel.com Subject: Re: [BUG] sched/cache: "Make LLC id continuous" causes NULL cpumask dereference in build_sched_domains on POWER9 Message-ID: Reply-To: Srikar Dronamraju References: <51154de7-3700-4cb4-82f2-1b3a8fa427f7@linux.ibm.com> <74a61427-b5d8-41ad-bc5b-508ee246d510@linux.ibm.com> <3498bef8-8835-4971-a753-029d73acffc7@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <3498bef8-8835-4971-a753-029d73acffc7@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 6ZWVZ3rgDYbEFh5xFZE3knNj12WlmH8p X-Proofpoint-GUID: 6ZWVZ3rgDYbEFh5xFZE3knNj12WlmH8p X-Authority-Analysis: v=2.4 cv=XqfK/1F9 c=1 sm=1 tr=0 ts=6a18710d cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=8nJEP1OIZ-IA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=eWJfLxs8EZ6PmFCxo0MA:9 a=wPNLvfGTeEIA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTI4MDE2OCBTYWx0ZWRfX1AFrfqxkkfas YIdCBvVxb1MOV7THUy8JlX9/5pI8ltFuReYu2o+isbK+k2sy0m3QGMEXqwQ0xZVomrTha/wsC5x 3RhPsza+AC4baLIfXY8DiTqd93Yi2VYOGVAUHTKxYXivguw5vwJ6WjEXDtKLZAdbbB8j80CsI5k KXaMKNSb/D1VgzQzf/uJUZBvldQ4D/yFlnT6Ye4KBHxMAn5ee8P3xo9wE0EpkSk6Pcw99mNWulQ PDxytvStRsfTIyhiKoQe/o4uglnt7CGpCrxcki4uOpyk1lx6o1/Sq8PqvibRfSnQMokAOaRaq+A X9bjNjjcOyblnU3WtpoezzCCMUcirDnTY52zP4oCrp1z8lpVHb+Uwap3mAXNXl6wkQVOLfsKDTR pXBDTZ7tZPYxB6RhZSCfEaY2BhdsmdCDZ10RwtCN3Q+kEfg9l6mZgxcdpd7WMyT5WwqEaDsxZtv iQTEikSZMLXABby13sw== 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=2026-05-28_04,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 impostorscore=0 adultscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 bulkscore=0 suspectscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2605280168 * Shrikanth Hegde [2026-05-28 22:01:53]: > > > index 3467f86fd78f..cc8e87d6cae9 100644 > > > --- a/arch/powerpc/kernel/smp.c > > > +++ b/arch/powerpc/kernel/smp.c > > > @@ -1101,6 +1101,16 @@ const struct cpumask *cpu_die_mask(int cpu) > > > } > > > EXPORT_SYMBOL_GPL(cpu_die_mask); > > > +const struct cpumask *arch_llc_mask(int cpu) > > > +{ > > > + /* Power9, CACHE domain is the LLC*/ > > > + if (shared_caches) > > > + return cpu_l2_cache_mask(cpu); > > > + > > > + /* For others, SMT domain is the LLC*/ > > > + return cpu_smt_mask(cpu); > > > +} > > > > Why dont we do > > #define arch_llc_mask cpu_l2_cache_mask > > > > I would prefer to keep the abstraction. This leaves > room for implementation details. > We could always do that whenever we need it. But doing it now will confuse the reader. Why keep if and else when both are returning the same. -- Thanks and Regards Srikar Dronamraju