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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 , Shrikanth Hegde Subject: [PATCH v7 06/31] static_call: Add read-only-after-init static calls Date: Fri, 14 Nov 2025 16:01:08 +0100 Message-ID: <20251114150133.1056710-7-vschneid@redhat.com> In-Reply-To: <20251114150133.1056710-1-vschneid@redhat.com> References: <20251114150133.1056710-1-vschneid@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 9866F140021 X-Stat-Signature: knnxqixmcyf986qant65fi1c73mq3y8s X-HE-Tag: 1763132639-289283 X-HE-Meta: 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 tsYG7rPf iBF29NnM2elXAec6ZkIX4PmjdeUwMbP8i6z0XEc/3GhP9O6wJVSHZtjYaqbhiD8Gaj9Onzw5YcPqkfKJPPDOZwkKIIL2DRJg82mROJ8ViukPICHPpqegdD4ubPuQOqasvRG5K+KH/QE53VFjIHPw3RVD5X/2DLHc3m5PQ+OFaRLBC10p1o2sgAqptSwvkRyu7OkTdZykli7iC/zAFm90TBT5bly2bj2B+xzSPbcXFPguRlj0NqPrK7KBGSHkoL4f2U5AON1y3qJiMErIDFyxfXZ+DmLSqPbb0EckZyGVAOoRPH+LxFdQjDUUtt9WlqvRUq/POkMIV71M8etT59SXBsg8nRAIZ5eLxkppw7i+KvbTSzSWQvWOQ4dYT8p4N+n0fDIprtjbMGRupxwhbDNL+ehCifGjIL/TqIFAp9uW9j0QeQUUID4sg9YO8Mgx+w3WRlULPzzJwIzq8YfzdQoZJpI0xbXbHHjEs7Bbs 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