linux/include/asm-generic/barrier.h
Andrey Konovalov 76695af20c locking, arch: use WRITE_ONCE()/READ_ONCE() in smp_store_release()/smp_load_acquire()
Replace ACCESS_ONCE() macro in smp_store_release() and smp_load_acquire()
with WRITE_ONCE() and READ_ONCE() on x86, arm, arm64, ia64, metag, mips,
powerpc, s390, sparc and asm-generic since ACCESS_ONCE() does not work
reliably on non-scalar types.

WRITE_ONCE() and READ_ONCE() were introduced in the following commits:

  230fa253df ("kernel: Provide READ_ONCE and ASSIGN_ONCE")
  43239cbe79 ("kernel: Change ASSIGN_ONCE(val, x) to WRITE_ONCE(x, val)")

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Alexander Duyck <alexander.h.duyck@redhat.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/1438528264-714-1-git-send-email-andreyknvl@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-08-03 10:59:30 +02:00

123 lines
2.4 KiB
C

/*
* Generic barrier definitions, originally based on MN10300 definitions.
*
* It should be possible to use these on really simple architectures,
* but it serves more as a starting point for new ports.
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#ifndef __ASM_GENERIC_BARRIER_H
#define __ASM_GENERIC_BARRIER_H
#ifndef __ASSEMBLY__
#include <linux/compiler.h>
#ifndef nop
#define nop() asm volatile ("nop")
#endif
/*
* Force strict CPU ordering. And yes, this is required on UP too when we're
* talking to devices.
*
* Fall back to compiler barriers if nothing better is provided.
*/
#ifndef mb
#define mb() barrier()
#endif
#ifndef rmb
#define rmb() mb()
#endif
#ifndef wmb
#define wmb() mb()
#endif
#ifndef dma_rmb
#define dma_rmb() rmb()
#endif
#ifndef dma_wmb
#define dma_wmb() wmb()
#endif
#ifndef read_barrier_depends
#define read_barrier_depends() do { } while (0)
#endif
#ifdef CONFIG_SMP
#ifndef smp_mb
#define smp_mb() mb()
#endif
#ifndef smp_rmb
#define smp_rmb() rmb()
#endif
#ifndef smp_wmb
#define smp_wmb() wmb()
#endif
#ifndef smp_read_barrier_depends
#define smp_read_barrier_depends() read_barrier_depends()
#endif
#else /* !CONFIG_SMP */
#ifndef smp_mb
#define smp_mb() barrier()
#endif
#ifndef smp_rmb
#define smp_rmb() barrier()
#endif
#ifndef smp_wmb
#define smp_wmb() barrier()
#endif
#ifndef smp_read_barrier_depends
#define smp_read_barrier_depends() do { } while (0)
#endif
#endif /* CONFIG_SMP */
#ifndef smp_store_mb
#define smp_store_mb(var, value) do { WRITE_ONCE(var, value); mb(); } while (0)
#endif
#ifndef smp_mb__before_atomic
#define smp_mb__before_atomic() smp_mb()
#endif
#ifndef smp_mb__after_atomic
#define smp_mb__after_atomic() smp_mb()
#endif
#define smp_store_release(p, v) \
do { \
compiletime_assert_atomic_type(*p); \
smp_mb(); \
WRITE_ONCE(*p, v); \
} while (0)
#define smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
smp_mb(); \
___p1; \
})
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_GENERIC_BARRIER_H */