From: Will Deacon <will.deacon@arm.com>
To: mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH v2 2/5] locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()
Date: Tue, 24 Oct 2017 11:22:47 +0100 [thread overview]
Message-ID: <1508840570-22169-3-git-send-email-will.deacon@arm.com> (raw)
In-Reply-To: <1508840570-22169-1-git-send-email-will.deacon@arm.com>
In preparation for the removal of lockless_dereference(), which is the
same as READ_ONCE() on all architectures other than Alpha, add an
implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
used to head dependency chains on all architectures.
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
include/linux/compiler.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 08083186e54f..7d7b77da9716 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -242,6 +242,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
__read_once_size(&(x), __u.__c, sizeof(x)); \
else \
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
+ smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
__u.__val; \
})
#define READ_ONCE(x) __READ_ONCE(x, 1)
--
2.1.4
next prev parent reply other threads:[~2017-10-24 10:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-24 10:22 [PATCH v2 0/5] Get rid of lockless_dereference() Will Deacon
2017-10-24 10:22 ` [PATCH v2 1/5] linux/compiler.h: Split into compiler.h and compiler_types.h Will Deacon
2017-10-24 12:46 ` [tip:locking/core] " tip-bot for Will Deacon
2017-10-24 10:22 ` Will Deacon [this message]
2017-10-24 12:46 ` [tip:locking/core] locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE() tip-bot for Will Deacon
2017-10-24 10:22 ` [PATCH v2 3/5] locking/barriers: Convert users of lockless_dereference() " Will Deacon
2017-10-24 12:47 ` [tip:locking/core] " tip-bot for Will Deacon
2017-10-24 10:22 ` [PATCH v2 4/5] locking/barriers: Kill lockless_dereference() Will Deacon
2017-10-24 12:47 ` [tip:locking/core] " tip-bot for Will Deacon
2017-10-24 10:22 ` [PATCH v2 5/5] alpha: atomics: Add smp_read_barrier_depends() to release/relaxed atomics Will Deacon
2017-10-24 12:47 ` [tip:locking/core] locking/atomics/alpha: Add smp_read_barrier_depends() to _release()/_relaxed() atomics tip-bot for Will Deacon
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