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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 , 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: <20260829084901.GA776954@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4813D1A0003 X-Stat-Signature: g9wyoh8sbu131ybzwmfreeu7hz4d6k6i X-HE-Tag: 1787993364-174741 X-HE-Meta: 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 l72D2maU 8BpnBOIFg9q+yw1M6ss89nQ8pDHSWi4lAyFQGRaHJ+9LVAGYMKF7XlBXmJIe2u3R+MqeWOqo228Tq1AVPlvVJZkPybifLCzjwdKV4ATDvbUilqPNlOYmdQIbM3cX7aWiK30FFgHJnY3isfXckRPRCGcCmCewBSq671Z08fA+mfyrOEE91G+FFeDDzEhhymbQ2qdQB/9iErBPl8Vc= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 28, 2026 at 01:50:05PM -0700, David Stevens wrote: > > It should have. They're taking spinlock inside raw_spinlock and lockdep > > should very much warn about that by default. > > It does trylocks on spinlocks and local locks, inside of > alloc_pages_nolock_noprof(). Lockdep considers that safe. Argh, that alloc_pages_nolock thing is a horror show. > On PREEMPT_RT, it is necessary to skip the call to > alloc_pages_nolock_noprof() from under pi_lock, since with that > configuration spin_trylock can end up needing to take pi_lock. But at > least on !PREEMPT_RT, there is no risk of deadlock. Yeah, which puts the lie to that horrific hack Alexei did. We should probably teach lockdep about spin_trylock() not being safe and see the house of cards crumble.