From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: [PATCH v3 05/19] asm/rwonce: Remove smp_read_barrier_depends() invocation Date: Fri, 10 Jul 2020 17:51:49 +0100 Message-ID: <20200710165203.31284-6-will@kernel.org> References: <20200710165203.31284-1-will@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594399952; bh=gTXZQO1RyYx1KEQLncc7UQSL6etty75iDnDOorylNyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qPyTLF3pqs4qb8U2JHB2vHzU3ThHJ3PE1k3ZZAAEPzT80q2DNbs8iyNQFOoFd/cRV TdSU3YBe0OXAcoaCD0tdjrKCzw5McHlOyx8HVGl2NHy2tJp2UJHuW9xFuXvHeusZ4O 518hS8o32/DrYn3LkGZXqBF3E+Vl9slsioyn3KsE= In-Reply-To: <20200710165203.31284-1-will@kernel.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: linux-kernel@vger.kernel.org Cc: Joel Fernandes , Mark Rutland , "Michael S. Tsirkin" , Peter Zijlstra , Catalin Marinas , virtualization@lists.linux-foundation.org, Will Deacon , Arnd Bergmann , Alan Stern , Sami Tolvanen , Matt Turner , kernel-team@android.com, Marco Elver , Kees Cook , "Paul E. McKenney" , Boqun Feng , Ivan Kokshaysky , linux-arm-kernel@lists.infradead.org, Richard Henderson , Nick Desaulniers , linux-alpha@vger.kernel.org Alpha overrides __READ_ONCE() directly, so there's no need to use smp_read_barrier_depends() in the core code. This also means that __READ_ONCE() can be relied upon to provide dependency ordering. Acked-by: Paul E. McKenney Signed-off-by: Will Deacon --- include/asm-generic/rwonce.h | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h index f9dfa88fc04d..cc810f1f18ca 100644 --- a/include/asm-generic/rwonce.h +++ b/include/asm-generic/rwonce.h @@ -30,24 +30,16 @@ /* * Use __READ_ONCE() instead of READ_ONCE() if you do not require any - * atomicity or dependency ordering guarantees. Note that this may result - * in tears! + * atomicity. 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) \ -({ \ - __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \ - smp_read_barrier_depends(); \ - (typeof(x))__x; \ -}) - #define READ_ONCE(x) \ ({ \ compiletime_assert_rwonce_type(x); \ - __READ_ONCE_SCALAR(x); \ + __READ_ONCE(x); \ }) #define __WRITE_ONCE(x, val) \ @@ -74,12 +66,9 @@ unsigned long __read_once_word_nocheck(const void *addr) */ #define READ_ONCE_NOCHECK(x) \ ({ \ - unsigned long __x; \ - compiletime_assert(sizeof(x) == sizeof(__x), \ + compiletime_assert(sizeof(x) == sizeof(unsigned long), \ "Unsupported access size for READ_ONCE_NOCHECK()."); \ - __x = __read_once_word_nocheck(&(x)); \ - smp_read_barrier_depends(); \ - (typeof(x))__x; \ + (typeof(x))__read_once_word_nocheck(&(x)); \ }) static __no_kasan_or_inline -- 2.27.0.383.g050319c2ae-goog