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Wed, 5 Aug 2026 12:37:48 +0000 (GMT) Message-ID: <020411fc-80dc-45c7-82d7-a99e9f6f825b@linux.ibm.com> Date: Wed, 5 Aug 2026 18:07:47 +0530 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 12/17] s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS To: Peter Zijlstra Cc: Boqun Feng , Madhavan Srinivasan , "Christophe Leroy (CS GROUP)" , Ingo Molnar , Will Deacon , Waiman Long , Gary Guo , Alice Ryhl , Lyude Paul , Daniel Almeida , =?UTF-8?Q?Onur_=C3=96zkan?= , Miguel Ojeda , Danilo Krummrich , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Heiko Carstens References: <20260804161447.84806-1-boqun@kernel.org> <20260804161447.84806-13-boqun@kernel.org> <367a9709-eb79-4579-9405-fb8d89576413@linux.ibm.com> <20260805094219.GM687043@noisy.programming.kicks-ass.net> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <20260805094219.GM687043@noisy.programming.kicks-ass.net> 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-Authority-Analysis: v=2.4 cv=E6P9Y6dl c=1 sm=1 tr=0 ts=6a732ea6 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=ZyJnKh-eXZI1ZQXNzZIA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: p-gJtqEUf_s0ZyDRixCMX_Y9ellvZAYp X-Proofpoint-GUID: hyANpGKjZ3GmXWYVVnY7ktEq2Paf37DD X-Proofpoint-Spam-Info: AW1haW4tMjYwODA1MDA5OSBTYWx0ZWRfX1KTo+urDlKVg +H36vqZfEY5++vel8i9AnTQ465QjC71nBYdbFW7Nq/VAu3Z3yuDZ7uZ53mEmzGb4NbzEjTAWTCU j68HX/M71Kh2IctUeLLkeZrp2jFYNnE= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA1MDA5OSBTYWx0ZWRfX5Q/670/mq5gv behJji3KYKKQmwYuAUAQHMAl4LSHeJKwmCII/M2Onh2xPml8sMx9ONpt0PruNwF7fcCMqKpCbyl fv+WOCWwhrTvyKMIy1bOXcKpE+lNCnPeRyJMKQLvyiixWSdYxLkymnXaSKqVTPcyD7ljywhVh8a BvUY9iUTEgiEisG8rvrmQTh7Lfv3MxEg7MYQbz7/5F9F3Q+kkNveYNxYmdIRjNe+0UIL2Ic2pOG qJNb3OTw/4S0NHbzLaJqNOtDeyCFo99OJjYnbqZYdiaC42zjYNZRYOdYH9DVPRm0YhQnzwtJwaQ dKEsXGMCoqSo73vmmpJ83kp7Q6BxiolBCzcZzq6oi2kWblNuHWqOWQKDS+Z29u5vXdcxHG9SmIZ FrW4MV9c/3eDlDZEGtmmxP2ef3JirIGySRQwqzF9Vbq8ZBOtCu/GUcD2o2j/Uv/cKY50P1DxHKq yBVfIIYDnZ2L0YvPwyA== 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=2026-08-05_04,2026-08-04_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 priorityscore=1501 suspectscore=0 adultscore=0 spamscore=0 malwarescore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608050099 Hi Peter. On 8/5/26 3:12 PM, Peter Zijlstra wrote: > On Wed, Aug 05, 2026 at 01:57:04AM +0530, Shrikanth Hegde wrote: >> +maddy, christophe, >> >> On 8/4/26 9:44 PM, Boqun Feng wrote: >>> From: Heiko Carstens >>> >>> Convert s390's preempt_count to 64 bit, and change the preempt >>> primitives accordingly. >>> >> >>> + union { >>> + struct { >>> + __u32 need_resched; /* 0x03a8 */ >>> + __u32 count; /* 0x03ac */ >>> + } preempt; >>> + __u64 preempt_count; /* 0x03a8 */ >>> + }; >> >> >> This is interesting. So arm64, s390 will have similar implementation >> w.r.t to preempt_count. >> >> I guess PoC that i was trying for ppc64 is worth pursuing even more, >> since ppc64 is one missing major arch which still uses old method >> of querying tif_need_resched. >> With similar change ppc64 can set HAS_SEPARATE_PREEMPT_RESCHED_BITS too. > > Yes. PPC should be able to the same thing ARM64 does. Yes. I am thinking of moving it to PACA instead of keeping it in thread_info as PACA is a natural per-CPU storage. If i hit any major hurdle there, will use thread info similar to arm64.