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[213.44.135.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48716547649sm7811135e9.0.2026.03.24.12.46.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Mar 2026 12:46:11 -0700 (PDT) From: Valentin Schneider To: Shrikanth Hegde , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , Josh Poimboeuf , Paolo Bonzini , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Sami Tolvanen , "David S. Miller" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Mel Gorman , Andrew Morton , Masahiro Yamada , Han Shen , Rik van Riel , Jann Horn , Dan Carpenter , Oleg Nesterov , Juri Lelli , Clark Williams , Tomas Glozar , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik Subject: Re: [RFC PATCH v8 05/10] sched/isolation: Mark housekeeping_overridden key as __ro_after_init In-Reply-To: References: <20260324094801.3092968-1-vschneid@redhat.com> <20260324094801.3092968-6-vschneid@redhat.com> Date: Tue, 24 Mar 2026 20:46:09 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: AXesf03arX82k8H05uyAIgUTyKVO4ZlHT4kgTnpK9FM_1774381574 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0C71FC000D X-Stat-Signature: gbjwknfwrqfzny4cdensjyqzsfse6x57 X-HE-Tag: 1774381576-355552 X-HE-Meta: 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 ekS2BcuC PSCmI9P1KY7kqR3Be4hqM8yE2r7odkDhusJR8G77NvtyhkGttrv2V5/iPZzOkmaNbtWj6svIM4x3C0KFCDA0qvihgFIupkKeQDkNKPdxRVNM9j9OLnmJIBuKvoLuJBYGE1G4aT0fmrggm/P+0QM/c1wPrpZb/Bshp8NzA0TvwIxJPFNisVM2T4igBCtVwJVGcR62j+MuzW9PQVTjTczI6RN79U6/W7/b+x3a5bUM6ZQWQbAdyIf0KfaUxvqmloKoNzylLH05m8vYT6ehoSyfkqCVI/J0v7blB5MVlkUfJT0HS8iJomVWl6NMfoN+5Z4Q2ad75jsgm2R2iC85HJX6BIBOQyEWxLDnD2NFGMzUSAl5l1Qw3/0aWEF+5hOuJBemIBIwkBMLSqUD/Uvw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 24/03/26 20:47, Shrikanth Hegde wrote: > On 3/24/26 3:17 PM, Valentin Schneider wrote: >> housekeeping_overridden is only ever enabled in the __init function >> housekeeping_init(), and is never disabled. Mark it __ro_after_init. >> > > what about housekeeping_update which could be via isolated_cpus_update > when creating isolated cpusets. > Doh, I'd even seen the patches but forgot to make a note of em. So yeah, that's not __init and the key is now flippable at runtime. I suppose I could resurrect: https://lore.kernel.org/lkml/20251114150133.1056710-6-vschneid@redhat.com/ + the is_kernel_noinstr_text() thing from https://lore.kernel.org/lkml/20251114151428.1064524-5-vschneid@redhat.com/ and have the IPI associated with flipping that key never be deferred, so if we suddenly have some CPU isolation, every CPU gets poked. >> Signed-off-by: Valentin Schneider >> --- >> kernel/sched/isolation.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c >> index 3ad0d6df6a0a2..54d1d93cdeea5 100644 >> --- a/kernel/sched/isolation.c >> +++ b/kernel/sched/isolation.c >> @@ -16,7 +16,7 @@ enum hk_flags { >> HK_FLAG_KERNEL_NOISE = BIT(HK_TYPE_KERNEL_NOISE), >> }; >> >> -DEFINE_STATIC_KEY_FALSE(housekeeping_overridden); >> +DEFINE_STATIC_KEY_FALSE_RO(housekeeping_overridden); >> EXPORT_SYMBOL_GPL(housekeeping_overridden); >> >> struct housekeeping {