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Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnaldo Carvalho de Melo , 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 , Yair Podemsky , Marcelo Tosatti , Daniel Wagner , Petr Tesarik Subject: [PATCH v6 06/29] static_call: Add read-only-after-init static calls Date: Fri, 10 Oct 2025 17:38:16 +0200 Message-ID: <20251010153839.151763-7-vschneid@redhat.com> In-Reply-To: <20251010153839.151763-1-vschneid@redhat.com> References: <20251010153839.151763-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Stat-Signature: za3s6ugyokoctgyfzzs3ujihk5go7gb7 X-Rspamd-Queue-Id: 4CE5B120008 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760110955-321238 X-HE-Meta: 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 voj8Sf7O 8PDt3g8FllhduzP6IhRpKbrFjiARII2UJhpNfEsXVPw93AI0cM/BVdavzNXJkdqXzAP6X7naPeZ4fRUDlz5aGU60Cq5GWq+999Gt8KD/b5RhOmLk7IHcOljBkXDPofm5ElSNiijOigJA3COAH21Lf2iRevla8zCVIgfgArPFyIdyYjegkgCSu677bcG67aPZ1TvYfKyoMZPcDgzXxJLWTGQN3zoSfvmltn+uoZ7kez8K1TgPkMKnu8C1U+XwhF+77r78RIy4zB6elYg5QQXQG1CPhAkVwGG02umpY4EAR8FXlA3mbUDFF6krlv99wvJzBuBnq26iP7tMxd394PYZyGtmKXvDWSGEHXcOLfDsd2fJRsj8ngow1r35R82LxPvfAeDHX+c7RgTQKrKiEb/NYoJdcSFMHgwWcZvdkkXvgD7rBEh02bNtiHCZaykn4Bp2wmY2jvaYeHN+9Mz52rS79UCst+xBouw4caKqz X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Josh Poimboeuf Deferring a code patching IPI is unsafe if the patched code is in a noinstr region. In that case the text poke code must trigger an immediate IPI to all CPUs, which can rudely interrupt an isolated NO_HZ CPU running in userspace. If a noinstr static call only needs to be patched during boot, its key can be made ro-after-init to ensure it will never be patched at runtime. Signed-off-by: Josh Poimboeuf --- include/linux/static_call.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/include/linux/static_call.h b/include/linux/static_call.h index 78a77a4ae0ea8..ea6ca57e2a829 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -192,6 +192,14 @@ extern long __static_call_return0(void); }; \ ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func) +#define DEFINE_STATIC_CALL_RO(name, _func) \ + DECLARE_STATIC_CALL(name, _func); \ + struct static_call_key __ro_after_init STATIC_CALL_KEY(name) = {\ + .func = _func, \ + .type = 1, \ + }; \ + ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func) + #define DEFINE_STATIC_CALL_NULL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ @@ -200,6 +208,14 @@ extern long __static_call_return0(void); }; \ ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) +#define DEFINE_STATIC_CALL_NULL_RO(name, _func) \ + DECLARE_STATIC_CALL(name, _func); \ + struct static_call_key __ro_after_init STATIC_CALL_KEY(name) = {\ + .func = NULL, \ + .type = 1, \ + }; \ + ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) + #define DEFINE_STATIC_CALL_RET0(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ -- 2.51.0