From: Peter Zijlstra <peterz@infradead.org>
To: David Stevens <stevensd@google.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Dave Chinner <david@fromorbit.com>, Qi Zheng <qi.zheng@linux.dev>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Uladzislau Rezki <urezki@gmail.com>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R . Howlett" <liam@infradead.org>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Kees Cook <kees@kernel.org>,
Clark Williams <clrkwllms@kernel.org>,
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
Date: Sat, 29 Aug 2026 10:49:01 +0200 [thread overview]
Message-ID: <20260829084901.GA776954@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CAOiLmNHrbXeTY7zoNodmaZUoMWf+NgvGvZ_LjfWD-1sKAoiLeQ@mail.gmail.com>
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.
next prev parent reply other threads:[~2026-08-29 8:49 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-27 23:29 [RFC 00/10] Reclaimable kernel stacks David Stevens
2026-08-27 23:29 ` [RFC 01/10] Add !MEMCG memcg_list_lru_alloc implementation David Stevens
2026-08-27 23:29 ` [RFC 02/10] mm/vmalloc: Skip vmallocinfo NUMA stats for VM_SPARSE David Stevens
2026-08-27 23:29 ` [RFC 03/10] fork: refactor vmap stack alloc/free into helpers David Stevens
2026-08-27 23:29 ` [RFC 04/10] mm: vmalloc: support creating aligned vm areas David Stevens
2026-08-27 23:29 ` [RFC 05/10] fork: allocate reclaimable stacks with VM_SPARSE David Stevens
2026-08-27 23:29 ` [RFC 06/10] Reclaim memory from blocked kernel stacks David Stevens
2026-08-28 11:54 ` Peter Zijlstra
2026-08-28 12:01 ` Peter Zijlstra
2026-08-28 12:04 ` Peter Zijlstra
2026-08-29 0:18 ` David Stevens
2026-08-29 8:39 ` Peter Zijlstra
2026-08-29 8:43 ` Peter Zijlstra
2026-08-28 12:41 ` Peter Zijlstra
2026-08-28 12:57 ` Peter Zijlstra
2026-08-28 23:33 ` David Stevens
2026-08-28 13:36 ` Sebastian Andrzej Siewior
2026-08-28 13:59 ` Peter Zijlstra
2026-08-28 14:25 ` Peter Zijlstra
2026-08-28 15:58 ` Sebastian Andrzej Siewior
2026-08-28 15:10 ` Sebastian Andrzej Siewior
2026-08-28 19:08 ` Steven Rostedt
2026-08-28 19:13 ` Steven Rostedt
2026-08-28 19:17 ` Steven Rostedt
2026-08-28 20:50 ` David Stevens
2026-08-29 8:49 ` Peter Zijlstra [this message]
2026-08-29 14:49 ` Matthew Wilcox
2026-08-28 21:17 ` David Stevens
2026-08-27 23:29 ` [RFC 07/10] Reclaim stacks via a shrinker David Stevens
2026-08-27 23:29 ` [RFC 08/10] Set PF_RECLAIMABLE_STACK in various places David Stevens
2026-08-28 6:33 ` K Prateek Nayak
2026-08-27 23:29 ` [RFC 09/10] x86: Enable reclaimable stacks David Stevens
2026-08-27 23:29 ` [RFC 10/10] arm64: " David Stevens
2026-08-28 12:47 ` [RFC 00/10] Reclaimable kernel stacks Peter Zijlstra
2026-08-28 14:33 ` Steven Rostedt
2026-08-28 14:35 ` Peter Zijlstra
2026-08-28 14:45 ` Peter Zijlstra
2026-08-28 16:10 ` Steven Rostedt
2026-08-28 17:58 ` David Stevens
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