From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Will Deacon <will@kernel.org>, Yunjae Lee <lyj7694@gmail.com>,
SeongJae Park <sj38.park@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Matt Turner <mattst88@gmail.com>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Richard Henderson <rth@twiddle.net>,
Peter Zijlstra <peterz@infradead.org>,
Alan Stern <stern@rowland.harvard.edu>,
Michael Ellerman <mpe@ellerman.id.au>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
Joe Perches <joe@perches.com>, Boqun Feng <boqun.feng@gmail.com>,
linux-alpha@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: [PATCH 03/13] READ_ONCE: Allow __READ_ONCE_SIZE cases to be overridden by the architecture
Date: Fri, 8 Nov 2019 17:01:10 +0000 [thread overview]
Message-ID: <20191108170120.22331-4-will@kernel.org> (raw)
In-Reply-To: <20191108170120.22331-1-will@kernel.org>
The meat and potatoes of 'READ_ONCE()' is defined by the
'__READ_ONCE_SIZE()' macro, which uses 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.
Signed-off-by: Will Deacon <will@kernel.org>
---
include/asm-generic/rwonce.h | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h
index abf326634ecd..2c2ac0948c94 100644
--- a/include/asm-generic/rwonce.h
+++ b/include/asm-generic/rwonce.h
@@ -33,13 +33,29 @@
#include <asm/barrier.h>
+#ifndef __read_once_size_1
+#define __read_once_size_1(p) (*(volatile __u8 *)(p))
+#endif
+
+#ifndef __read_once_size_2
+#define __read_once_size_2(p) (*(volatile __u16 *)(p))
+#endif
+
+#ifndef __read_once_size_4
+#define __read_once_size_4(p) (*(volatile __u32 *)(p))
+#endif
+
+#ifndef __read_once_size_8
+#define __read_once_size_8(p) (*(volatile __u64 *)(p))
+#endif
+
#define __READ_ONCE_SIZE \
({ \
switch (size) { \
- case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
- case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
- case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
- case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
+ case 1: *(__u8 *)res = __read_once_size_1(p); break; \
+ case 2: *(__u16 *)res = __read_once_size_2(p); break; \
+ case 4: *(__u32 *)res = __read_once_size_4(p); break; \
+ case 8: *(__u64 *)res = __read_once_size_8(p); break; \
default: \
barrier(); \
__builtin_memcpy((void *)res, (const void *)p, size); \
@@ -59,6 +75,10 @@ void __read_once_size_nocheck(const volatile void *p, void *res, int size)
__READ_ONCE_SIZE;
}
+#undef __read_once_size_1
+#undef __read_once_size_2
+#undef __read_once_size_4
+#undef __read_once_size_8
#undef __READ_ONCE_SIZE
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
--
2.24.0.rc1.363.gb1bccd3e3d-goog
next prev parent reply other threads:[~2019-11-08 17:01 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 17:01 [PATCH 00/13] Finish off [smp_]read_barrier_depends() Will Deacon
2019-11-08 17:01 ` [PATCH 01/13] compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h Will Deacon
2019-11-08 19:57 ` Arnd Bergmann
2019-11-11 8:10 ` Christian Borntraeger
2019-11-11 9:32 ` Arnd Bergmann
2019-11-12 11:36 ` Will Deacon
2019-11-08 17:01 ` [PATCH 02/13] READ_ONCE: Undefine internal __READ_ONCE_SIZE macro after use Will Deacon
2019-11-08 17:01 ` Will Deacon [this message]
2019-11-08 17:01 ` [PATCH 04/13] vhost: Remove redundant use of read_barrier_depends() barrier Will Deacon
2019-11-08 17:01 ` [PATCH 05/13] alpha: Override READ_ONCE() with barriered implementation Will Deacon
2019-11-08 17:01 ` [PATCH 06/13] READ_ONCE: Remove smp_read_barrier_depends() invocation Will Deacon
2019-11-08 17:01 ` [PATCH 07/13] alpha: Replace smp_read_barrier_depends() usage with smp_[r]mb() Will Deacon
2019-11-08 17:01 ` [PATCH 08/13] locking/barriers: Remove definitions for [smp_]read_barrier_depends() Will Deacon
2019-11-08 17:01 ` [PATCH 09/13] Documentation/barriers: Remove references to [smp_]read_barrier_depends() Will Deacon
2019-11-21 19:32 ` [PATCH] Documentation/barriers/kokr: " SeongJae Park
2019-11-26 22:20 ` Paul E. McKenney
2019-11-29 18:08 ` [PATCH v2] " SeongJae Park
2019-12-06 17:20 ` SeongJae Park
2019-12-06 20:44 ` Paul E. McKenney
2019-12-06 21:29 ` SeongJae Park
2019-12-06 22:08 ` Paul E. McKenney
2019-12-06 22:38 ` SeongJae Park
2019-12-06 22:51 ` Paul E. McKenney
2019-12-09 9:44 ` Will Deacon
2019-12-09 17:00 ` Paul E. McKenney
2019-12-09 17:06 ` Will Deacon
2019-12-09 17:43 ` SeongJae Park
2019-11-08 17:01 ` [PATCH 10/13] tools/memory-model: Remove smp_read_barrier_depends() from informal doc Will Deacon
2019-11-08 17:42 ` Alan Stern
2019-11-08 17:01 ` [PATCH 11/13] powerpc: Remove comment about read_barrier_depends() Will Deacon
2019-11-20 10:37 ` Michael Ellerman
2019-11-26 22:24 ` Paul E. McKenney
2019-11-08 17:01 ` [PATCH 12/13] include/linux: Remove smp_read_barrier_depends() from comments Will Deacon
2019-11-08 17:01 ` [PATCH 13/13] checkpatch: Remove checks relating to [smp_]read_barrier_depends() Will Deacon
2019-11-08 18:50 ` [PATCH 00/13] Finish off [smp_]read_barrier_depends() Paul E. McKenney
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