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Tue, 29 Sep 2026 10:46:51 -0700 (PDT) From: Kayra Cizmeci To: peterz@infradead.org Cc: bsegall@google.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org, mgorman@suse.de, mingo@kernel.org, rostedt@goodmis.org, tj@kernel.org, vincent.guittot@linaro.org, vschneid@redhat.com Subject: Re: [PATCH v2 4/4] sched/fair: Rework/fix task_h_load() Date: Tue, 29 Sep 2026 20:46:47 +0300 Message-ID: <20260929174648.196105-1-kayracizmeci@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260929085320.337703476@infradead.org> References: <20260929085320.337703476@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Peter, (Fun Stuff): > @@ -15731,6 +15766,8 @@ static int __sched_group_set_shares(stru > update_load_avg(cfs_rq, se, UPDATE_TG); > update_cfs_group(se); > } > + for_each_sched_entity_bl(se, cfs_rq) > + update_cfs_rq_h_load(group_cfs_rq(se), se, cfs_rq); > rq_unlock_irqrestore(rq, &rf); > } > So, the code is this: #define for_each_sched_entity(se, cfs_rq) \ for (struct sched_entity *_BL = NULL; \ (se) && ((cfs_rq) = cfs_rq_of(se), (cfs_rq)->backlink = _BL, true);\ (se) = (se)->parent, _BL = (se)) #define for_each_sched_entity_bl(se, cfs_rq) \ for (; ((se) = (cfs_rq)->backlink); (cfs_rq) = group_cfs_rq(se)) (While writing this, a suitcase tried to assassinate me by falling from top of the closet, what follows after this part may be the symptoms of my brain-damage.) Let's say we have a *thing* like this: +----+ +----+ +------+ |se_a| -> |rq_a| -> |task_a| +----+ +----+ +------+ | | | V +----+ +----+ +------+ |se_b| -> |rq_b| -> |task_b| +----+ +----+ +------+ When we start as task_b, everything goes well. Both groups are updated. On task_a too, only se_a is updated. But when we start as se_a root's backlink is NULL so we don't update anything. While on se_b rq_a's backlink is NULL and update se_a but not ourselfes. I don't think this is that of a problem tho, and I could be missing something. (Ultra-Fun Stuff (Maybe)): Also, I saw you making an Assisted-by joke yesterday so... Assisted-by: Fingers (Typing) Assisted-by: Luck (Born) Assisted-by: Computer (IDK) Assisted-by: Knowledge (Knowledge) Assisted-by: Linux Itself (Kernel) Assisted-by: EEVDF (I mean...) Assisted-by: Water Assisted-by: Energy (I don't have any ;<) Assisted-by: Sun Assisted-by: Universe Assisted-by: Editor Assisted-by: LKML Assisted-by: LWN Assisted-by: Music (Vibes) Assisted-by: Heart (Broken ;<) Assisted-by: Brain (Damaged a bit) There could be more :p Thanks, Kayra