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Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Uladzislau Rezki , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Clark Williams , suleiman@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-rt-devel@lists.linux.dev Subject: Re: [RFC 06/10] Reclaim memory from blocked kernel stacks Message-ID: <20260831070733.GS687043@noisy.programming.kicks-ass.net> References: <20260827232948.2520558-1-stevensd@google.com> <20260827232948.2520558-7-stevensd@google.com> <20260828133620._x2XfJR_@linutronix.de> <20260828135947.GU776954@noisy.programming.kicks-ass.net> <20260828151018.HnR9xV1N@linutronix.de> <20260828150836.2d5b378c@gandalf.local.home> <20260828151313.5c4a5e4b@gandalf.local.home> <20260828151747.20035d50@gandalf.local.home> <20260831065509.qqEtERDB@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260831065509.qqEtERDB@linutronix.de> X-Stat-Signature: 1bbbwneg6zxeeahrrc4rjj9ucbhkbkxp X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 086331A0003 X-Rspam-User: X-HE-Tag: 1788160068-967590 X-HE-Meta: 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 5tsRafA5 kWeAl7ZvABRLnPkJ3JFt0T6GsOiALiy3JMOnafOzYpUUvqWuHppVO5C0m9czzXjj47VQYXrdZyPvwul/l9S1X7tAuEHTSQpGRIR4SvQLTogBUsa4Ef8fJRlL2p9P7gGUP+8cAmPFqzRfdyo8XSGr0ckk2zhnxsBUmp2t0aafKnNI8jUvbTOrVmKWkGz8QZY1rcDo7O5vj8pbbCOg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 31, 2026 at 08:55:09AM +0200, Sebastian Andrzej Siewior wrote: > (stack tracer running) > Depth Size Location (60 entries) > ----- ---- -------- > 0) 8176 48 __css_rstat_updated+0x9/0x150 > 1) 8128 8 __cgroup_account_cputime+0x2f/0x50 > 2) 8120 48 update_se+0x10c/0x1b0 > 3) 8072 48 update_curr+0x31/0x180 > 4) 8024 56 put_prev_entity+0x153/0x1f0 > 5) 7968 136 pick_next_task_fair+0x684/0x8e0 > 6) 7832 120 __schedule+0x1ca/0x1130 > 7) 7712 8 preempt_schedule_irq+0x38/0x60 > 8) 7704 72 irqentry_exit+0x148/0x6b0 > 9) 7632 136 asm_sysvec_apic_timer_interrupt+0x1a/0x20 > 10) 7496 240 HUF_compress1X_usingCTable_internal_bmi2+0x12d2/0x1c40 > > Does this stack tracer distinguish between the kernel-stack and > IRQ-stack? I would expect asm_sysvec_apic_timer_interrupt() on the > IRQ-stack and not adding weight to the kernel stack. This is the return from interrupt path, irqentry_exit() is right after we switch back from the IRQ stack and are back on the task stack. We have to be, in order to schedule the task and all that.