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Wed, 25 Feb 2026 17:47:53 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay03.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 61PHlndC52429258 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 25 Feb 2026 17:47:49 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3A34020043; Wed, 25 Feb 2026 17:47:49 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E6F2A20040; Wed, 25 Feb 2026 17:47:42 +0000 (GMT) Received: from [9.124.222.200] (unknown [9.124.222.200]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 25 Feb 2026 17:47:42 +0000 (GMT) Message-ID: <62f50aad-05ce-42ac-bdf6-dcb4af69c1c2@linux.ibm.com> Date: Wed, 25 Feb 2026 23:17:42 +0530 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/15] powerpc/time: Prepare to stop elapsing in dynticks-idle To: "Christophe Leroy (CS GROUP)" , Frederic Weisbecker , LKML , Madhavan Srinivasan Cc: "Rafael J. Wysocki" , Alexander Gordeev , Anna-Maria Behnsen , Ben Segall , Boqun Feng , Christian Borntraeger , Dietmar Eggemann , Heiko Carstens , Ingo Molnar , Jan Kiszka , Joel Fernandes , Juri Lelli , Kieran Bingham , Mel Gorman , Michael Ellerman , Neeraj Upadhyay , Nicholas Piggin , "Paul E . McKenney" , Peter Zijlstra , Steven Rostedt , Sven Schnelle , Thomas Gleixner , Uladzislau Rezki , Valentin Schneider , Vasily Gorbik , Vincent Guittot , Viresh Kumar , Xin Zhao , linux-pm@vger.kernel.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org References: <20260206142245.58987-1-frederic@kernel.org> <20260206142245.58987-5-frederic@kernel.org> <9413517d-963b-4e6d-b11b-b440acd7cb5a@linux.ibm.com> <9ab1e7d7-57ee-49f9-963c-3a1b96dda684@kernel.org> <120884b0-0b09-43a9-b0f6-7dc2affe1ac0@linux.ibm.com> <55720b5b-f643-4e67-8841-d81a9e712faf@kernel.org> <729a7e7f-a50e-480c-87ce-c45221fbb326@linux.ibm.com> <6c007cf1-46d5-4853-ae2e-90ee5257c6c9@kernel.org> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <6c007cf1-46d5-4853-ae2e-90ee5257c6c9@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjI1MDE2OSBTYWx0ZWRfXyoXr+gaINCkX swtLpILwXDJFyN/y0EQ/PZ6BsXh7ez8fMiRIFQX1Kuvmd0cTkULq2NEg+gsiOSUI9+8+V/bfqvt BCEwPgwsRHOUNk8y2Fm7+NOe+fRW3mrNjsOctq3c0QFljM91aj1CDDETUkQLYEhDrZrJs+gfc4T 0KHhGDrntMSNoRCLDSVrvPGA7tApvjLpc8Dc3OlpCiRs1UVE06uKamvhqS6W2j5R7XKlsu2U5pZ Mfimy3SZ2nCMFT8pZvPMyT8rwDKzYBdDkKhMNMbeOTyyLViJhQSOBITwdWbY0ftlpRtviwTdfO2 FMD9AtfmjzbbVWVlSfxd2GUx6KH96iwpcENvdcZnlTxRb70VSdeHd/WFnivdjuy8emwMld1JZAC /95Np8ehXGeW2R/LePIcVP7WGBjvoGjU0puVnGn5JcTeHs+p3/SW48g6jPQJQBA6ffhQsGNftVM 8031OmFKUBPXwq3YhXg== X-Proofpoint-ORIG-GUID: Tv4S2untdyEH1R38ppz_YIjtG6ZEtY6R X-Authority-Analysis: v=2.4 cv=F9lat6hN c=1 sm=1 tr=0 ts=699f35ca cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=lk4ULvty7AM7_XruhlkA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: kqxW0WId8-MSaE3TJ8tfVvU82vXknTAu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-25_02,2026-02-25_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 bulkscore=0 adultscore=0 spamscore=0 clxscore=1015 suspectscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602250169 Hi Christophe. > I think I'm starting to understand now. > > I think the problem is that acct->starttime has an invalid value the > very first time it is used. > > We are probably lacking an initial value in paca->accounting.starttime. > This should likely be initialised from mftb in head_64.S in > start_here_common for main CPU and __secondary_start for other CPUs or > maybe at higher level in C in setup_arch() and start_secondary() > > Christophe How about below? this works too. --- diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 18506740f4a4..af129645b7f7 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -928,9 +928,24 @@ static void __init set_decrementer_max(void) bits, decrementer_max); } +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE +/* + * This is done to initialize the starttime correctly. with this + * /proc/stat show correct values similar to CONFIG_VIRT_CPU_ACCOUNTING_GEN + */ +static void init_cpu_accounting_startime(void) +{ + struct cpu_accounting_data *acct = get_accounting(current); + acct->starttime = mftb(); +} +#else +static void init_cpu_accounting_startime(void) { }; +#endif + static void __init init_decrementer_clockevent(void) { register_decrementer_clockevent(smp_processor_id()); + init_cpu_accounting_startime(); } void secondary_cpu_time_init(void) @@ -946,6 +961,8 @@ void secondary_cpu_time_init(void) /* FIME: Should make unrelated change to move snapshot_timebase * call here ! */ register_decrementer_clockevent(smp_processor_id()); + + init_cpu_accounting_startime(); } /*