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Wed, 14 Oct 2026 16:28:05 +0000 (GMT) Received: from [9.124.214.100] (unknown [9.124.214.100]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 14 Oct 2026 16:28:05 +0000 (GMT) Message-ID: <4976fcef-29ec-43fd-8655-32874720ee73@linux.ibm.com> Date: Wed, 14 Oct 2026 21:58:04 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 07/18] sched/fair: Add push task mechanism for fair To: Vincent Guittot Cc: qyousef@layalina.io, christian.loehle@arm.com, pierre.gondois@arm.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org, lukasz.luba@arm.com, rafael@kernel.org, linux-pm@vger.kernel.org, tj@kernel.org, void@manifault.com, arighi@nvidia.com, changwoo@igalia.com, sched-ext@lists.linux.dev References: <20261002154415.2270586-1-vincent.guittot@linaro.org> <20261002154415.2270586-8-vincent.guittot@linaro.org> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: 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: AW1haW4tMjYxMDE0MDA2NCBTYWx0ZWRfXwpB1IwT3mpYt ImehsQLFHJJx5ewZqk/wWa0G3Vr4dTqzdurXncBk/x96bXRJLkwyylg+nbvYMsAyMGeK5hKNE6F F2wBWp5hS2KWNFUO7UAMc3fEw4mwi5UN2D+jw2CQbuhz7ew9V+De9gI881je83KVpKic5sFuvQY pYFKKIaoh/gxD7MJQfrdDjkwWzHuzb39cGJcX+/qBslnuQvtVxc9Wm/hXfgV2JeVQYf/cJtezwe 4+zLSDpeYEgFMwyx5iZt2UxZLs20U++kuCcP4cyfK1XomcUqFR2oQAXurWf64ncVA8dkS614i2a KZQQY+iDOf5Kp4A9EV7/a/+Rjw+FQzxkAluh3eBMxP6k6FqopsxG8mblj8HE7Kg3IFJSNI07XBQ BrYSH6BfDxLEkfupHThXEWgrtxL9Gri6qSH53/P0PVxBMEcjd+PWpS7ThtVVNLeHg+A/EfwYgIM /ZxMlKSIUaEj+8onDrQ== X-Proofpoint-GUID: bTnntmyhciz6VMQGtL75Hn2xX8z57U3F X-Proofpoint-ORIG-GUID: f5RArQspwIy94p8IOOSF3AEcgcep3yTw X-Proofpoint-Spam-Info: AW1haW4tMjYxMDE0MDA2NCBTYWx0ZWRfX+XnNPF9Vjits UzkEu6haHnvxSrVR3jIUZVoRXNewSL97nw6D5kirRtRcN0XvHqKpyzZpNydZU0liTw9TtFoRFID Cqtc1htVFC2R0OAF4ZuRKTqqIccBQec= X-Authority-Analysis: v=2.4 cv=btHZl0ai c=1 sm=1 tr=0 ts=6acfad9e cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=tYy84T6U5ddJezyHrlAA:9 a=QEXdDO2ut3YA:10 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=2026-10-13_01,2026-10-14_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 malwarescore=0 phishscore=0 impostorscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 clxscore=1015 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610140064 >>> +static int >>> +select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags); >>> + >>> +/* >>> + * See if the non running fair tasks on this rq can be sent on other CPUs >>> + * that fits better with their profile. >>> + */ >>> +static bool fair_push_task(struct rq *rq) >>> +{ >>> + struct task_struct *next_task; >>> + int prev_cpu, new_cpu; >>> + struct rq_flags rf; >>> + struct rq *cur_rq; >> >> You likely need below to keep clang's context tracking to be happy. >> >> context_unsafe_alias(rq); > > I just noticed that I didn't answer to this one > > Why should I need this ? > > rq remains the same in fair_push_task(). I'm using rq and new_rq to > differentiate both current and new rq > >> I tried to use clang-23 and get below with the series applied. It may not be exactly here. But somewhere. make LLVM=/opt/llvm-23/bin/ \ KCFLAGS="-Werror=thread-safety-analysis" \ V=1 kernel/sched/fair.o kernel/sched/fair.c:9971:2: error: releasing raw_spinlock 'rq_lockp(rq)' that was not held [-Werror,-Wthread-safety-analysis] 9971 | raw_spin_rq_unlock(rq); | ^ kernel/sched/fair.c:9983:2: error: raw_spinlock 'rq_lockp(rq)' is not held on every path through here [-Werror,-Wthread-safety-analysis] 9983 | raw_spin_unlock(&next_task->pi_lock); | ^ ./include/linux/spinlock.h:279:32: note: expanded from macro 'raw_spin_unlock' 279 | #define raw_spin_unlock(lock) _raw_spin_unlock(lock) | ^ kernel/sched/fair.c:9980:2: note: raw_spinlock acquired here 9980 | raw_spin_rq_lock(rq); | ^ kernel/sched/fair.c:10085:2: error: releasing raw_spinlock 'rq_lockp(rq)' that was not held [-Werror,-Wthread-safety-analysis] 10085 | rq_unlock(rq, rf); | ^ kernel/sched/fair.c:10093:1: error: raw_spinlock 'rq_lockp(rq)' is not held on every path through here [-Werror,-Wthread-safety-analysis] 10093 | } | ^ kernel/sched/fair.c:10090:2: note: raw_spinlock acquired here 10090 | rq_lock(rq, rf); | ^