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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: <20260828120113.GM687043@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-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4FA9E20013 X-Stat-Signature: u9s1nwux1o5x454rkhbbe73kagoyusfk X-HE-Tag: 1787918495-25598 X-HE-Meta: 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 SJgmjqGK SyXx9iJdV8UOiM030ysKM5LR6LOaUQ/BnB4lc8lcxpTFDZeJTmULDgl4dNOzRhByYMoPhhaj7coNzTeTnrChCL/MJ8xCH4iCHWLIRdzxZ2MTn/IEb+/gAOYxE8p2/KZ373cGtaTE99CxrqZ1Jij/koC+w/QnA42peD6s3XE/spnBT3Agfd1xdIfN77tTdi/lj+Rqq3ArnnN8xss4= 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: > @@ -4295,8 +4296,6 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) > if (!ttwu_state_match(p, state, &success)) > break; > > - trace_sched_waking(p); > - > /* > * Ensure we load p->on_rq _after_ p->state, otherwise it would > * be possible to, falsely, observe p->on_rq == 0 and get stuck > @@ -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); > > /* > * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be Don't move that tracepoint. That's simply lying about how long it takes to wake up the task.