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From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Jason Wang <jasowang@redhat.com>,
	virtualization@lists.linux-foundation.org,
	Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Alan Stern <stern@rowland.harvard.edu>,
	Sami Tolvanen <samitolvanen@google.com>,
	Matt Turner <mattst88@gmail.com>,
	kernel-team@android.com, Marco Elver <elver@google.com>,
	Kees Cook <keescook@chromium.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	linux-arm-kernel@lists.infradead.org,
	Richard Henderson <rth@twiddle.net>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-alpha@vger.kernel.org
Subject: [PATCH 03/18] asm/rwonce: Allow __READ_ONCE to be overridden by the architecture
Date: Tue, 30 Jun 2020 18:37:19 +0100	[thread overview]
Message-ID: <20200630173734.14057-4-will@kernel.org> (raw)
In-Reply-To: <20200630173734.14057-1-will@kernel.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 <paulmck@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
 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


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  parent reply	other threads:[~2020-06-30 17:39 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30 17:37 [PATCH 00/18] Allow architectures to override __READ_ONCE() Will Deacon
2020-06-30 17:37 ` [PATCH 01/18] tools: bpf: Use local copy of headers including uapi/linux/filter.h Will Deacon
2020-07-01 16:38   ` Alexei Starovoitov
2020-06-30 17:37 ` [PATCH 02/18] compiler.h: Split {READ, WRITE}_ONCE definitions out into rwonce.h Will Deacon
2020-06-30 19:11   ` Arnd Bergmann
2020-07-01 10:16     ` [PATCH 02/18] compiler.h: Split {READ,WRITE}_ONCE " Will Deacon
2020-07-01 11:33       ` [PATCH 02/18] compiler.h: Split {READ, WRITE}_ONCE " Arnd Bergmann
2020-06-30 17:37 ` Will Deacon [this message]
2020-06-30 17:37 ` [PATCH 04/18] alpha: Override READ_ONCE() with barriered implementation Will Deacon
2020-07-02  9:32   ` Mark Rutland
2020-07-02  9:48     ` Will Deacon
2020-07-02 10:08       ` Arnd Bergmann
2020-07-02 11:18         ` Will Deacon
2020-07-02 11:39           ` Arnd Bergmann
2020-07-02 14:43   ` Joel Fernandes
2020-07-02 14:55     ` Will Deacon
2020-07-02 15:07       ` Joel Fernandes
2020-06-30 17:37 ` [PATCH 05/18] asm/rwonce: Remove smp_read_barrier_depends() invocation Will Deacon
2020-06-30 17:37 ` [PATCH 06/18] vhost: Remove redundant use of read_barrier_depends() barrier Will Deacon
2020-06-30 17:37 ` [PATCH 07/18] alpha: Replace smp_read_barrier_depends() usage with smp_[r]mb() Will Deacon
2020-06-30 17:37 ` [PATCH 08/18] locking/barriers: Remove definitions for [smp_]read_barrier_depends() Will Deacon
2020-06-30 17:37 ` [PATCH 09/18] Documentation/barriers: Remove references to [smp_]read_barrier_depends() Will Deacon
2020-06-30 17:37 ` [PATCH 10/18] Documentation/barriers/kokr: " Will Deacon
2020-06-30 17:37 ` [PATCH 11/18] tools/memory-model: Remove smp_read_barrier_depends() from informal doc Will Deacon
2020-06-30 17:37 ` [PATCH 12/18] include/linux: Remove smp_read_barrier_depends() from comments Will Deacon
2020-06-30 17:37 ` [PATCH 13/18] checkpatch: Remove checks relating to [smp_]read_barrier_depends() Will Deacon
2020-06-30 17:37 ` [PATCH 14/18] arm64: Reduce the number of header files pulled into vmlinux.lds.S Will Deacon
2020-06-30 17:37 ` [PATCH 15/18] arm64: alternatives: Split up alternative.h Will Deacon
2020-06-30 17:37 ` [PATCH 16/18] arm64: cpufeatures: Add capability for LDAPR instruction Will Deacon
2020-06-30 17:37 ` [PATCH 17/18] arm64: alternatives: Remove READ_ONCE() usage during patch operation Will Deacon
2020-06-30 17:37 ` [PATCH 18/18] arm64: lto: Strengthen READ_ONCE() to acquire when CLANG_LTO=y Will Deacon
2020-06-30 19:25   ` Arnd Bergmann
2020-07-01 10:19     ` Will Deacon
2020-07-01 10:59       ` Arnd Bergmann
2020-06-30 19:47   ` Marco Elver
2020-06-30 20:20     ` Peter Zijlstra
2020-06-30 22:57     ` Sami Tolvanen
2020-07-01 10:25       ` Will Deacon
2020-07-01 10:24     ` Will Deacon
2020-07-01 17:07   ` Dave P Martin
2020-07-02  7:23     ` Will Deacon
2020-07-06 16:00       ` Dave Martin
2020-07-06 16:34         ` Paul E. McKenney
2020-07-06 17:05           ` Dave Martin
2020-07-06 17:36             ` Paul E. McKenney
2020-07-07 10:29               ` Dave Martin
2020-07-07 22:51                 ` Paul E. McKenney
2020-07-07 23:01                   ` Nick Desaulniers
2020-07-08  7:15                     ` Marco Elver
2020-07-08  9:16                     ` Peter Zijlstra
2020-07-08 18:20                       ` Paul E. McKenney
2020-07-06 18:35         ` Will Deacon
2020-07-06 19:23           ` Marco Elver
2020-07-06 19:42             ` Paul E. McKenney
2020-07-06 16:08   ` Dave Martin
2020-07-06 18:35     ` Will Deacon
2020-07-07 10:10       ` Dave Martin
2020-07-01  7:38 ` [PATCH 00/18] Allow architectures to override __READ_ONCE() Josh Triplett

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