From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: [PATCH 03/18] asm/rwonce: Allow __READ_ONCE to be overridden by the architecture Date: Tue, 30 Jun 2020 18:37:19 +0100 Message-ID: <20200630173734.14057-4-will@kernel.org> References: <20200630173734.14057-1-will@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200630173734.14057-1-will@kernel.org> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Will Deacon , Sami Tolvanen , Nick Desaulniers , Kees Cook , Marco Elver , "Paul E. McKenney" , Josh Triplett , Matt Turner , Ivan Kokshaysky , Richard Henderson , Peter Zijlstra , Alan Stern , "Michael S. Tsirkin" , Jason Wang , Arnd Bergmann , Boqun Feng , Catalin Marinas , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.orgv List-Id: virtualization@lists.linuxfoundation.org The meat and potatoes of READ_ONCE() is defined by the __READ_ONCE() macro, which uses a volatile casts in an attempt to avoid tearing of byte, halfword, word and double-word accesses. Allow this to be overridden by the architecture code in the case that things like memory barriers are also required. Acked-by: Paul E. McKenney Signed-off-by: Will Deacon --- include/asm-generic/rwonce.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h index 92cc2f223cb3..f9dfa88fc04d 100644 --- a/include/asm-generic/rwonce.h +++ b/include/asm-generic/rwonce.h @@ -33,7 +33,9 @@ * atomicity or dependency ordering guarantees. Note that this may result * in tears! */ +#ifndef __READ_ONCE #define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x)) +#endif #define __READ_ONCE_SCALAR(x) \ ({ \ -- 2.27.0.212.ge8ba1cc988-goog