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Peter Anvin" , Andrew Morton , Dave Chinner , Qi Zheng , Roman Gushchin , Muchun Song , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , 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 , Sebastian Andrzej Siewior , 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: <20260828120408.GN687043@noisy.programming.kicks-ass.net> References: <20260827232948.2520558-1-stevensd@google.com> <20260827232948.2520558-7-stevensd@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260827232948.2520558-7-stevensd@google.com> X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: BA6F640018 X-Stat-Signature: tuujqk9yti5agygm58swdzwtzgc5hjgj X-Rspam-User: X-HE-Tag: 1787918656-484608 X-HE-Meta: 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 fmgWP6ML vgqwfBaGJ47GbvFCnlglAo6hQo1ejMrc88BiFCzyGJdIAO45FVH8j7QtzBQezMuZhKupwnr9co12X/xhMAECzlvvwjaDwWkzKo8OZW1kGH4zaVetzDf8M0OEjKKznYtELMXf2ZhFXh86mfO4UY92tawQ9COvRrd8as3vVyp/zYbVdWnBCICXOLmcs3eLtVHB0RRexxTAKZW6IAxGCBy3RkO0RAx2Q/0MUEN/18DnCknqya5w= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 27, 2026 at 04:29:44PM -0700, David Stevens wrote: > @@ -4320,8 +4319,18 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) > * A similar smp_rmb() lives in __task_needs_rq_lock(). > */ > smp_rmb(); > - if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) > + if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) { > + trace_sched_waking(p); > + break; > + } > + > + if (!ensure_stack_is_present(p, &need_deferred_repopulate)) { > + WRITE_ONCE(p->__state, TASK_STACK_RECLAIM); > + do_deferred_repopulate_wake = need_deferred_repopulate; > break; > + } > + > + trace_sched_waking(p); Absolutely not; ensure_stack_is_present() must not call repopulate_stack() while holding ->pi_lock. Not happening.