forked from mirrors/linux
9fa45070a2
As a step to ensuring the atomic* APIs are consistent, switch to fallbacks generated by gen-atomic-fallback.sh. These are checked in rather than generated with Kbuild, since: * This allows inspection of the atomics with git grep and ctags on a pristine tree, which Linus strongly prefers being able to do. * The fallbacks are not affected by machine details or configuration options, so it is not necessary to regenerate them to take these into account. * These are included by files required *very* early in the build process (e.g. for generating bounds.h), and we'd rather not complicate the top-level Kbuild file with dependencies. The new fallback header should be equivalent to the old fallbacks in <linux/atomic.h>, but: * It is formatted a little differently due to scripting ensuring things are more regular than they used to be. * Fallbacks are now expanded in-place as static inline functions rather than macros. * The prototypes for fallbacks are arragned consistently with the return type on a separate line to try to keep to a sensible line length. There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will.deacon@arm.com> Cc: linux-arm-kernel@lists.infradead.org Cc: catalin.marinas@arm.com Cc: linuxdrivers@attotech.com Cc: dvyukov@google.com Cc: Boqun Feng <boqun.feng@gmail.com> Cc: arnd@arndb.de Cc: aryabinin@virtuozzo.com Cc: glider@google.com Link: http://lkml.kernel.org/r/20180904104830.2975-3-mark.rutland@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
78 lines
2.2 KiB
C
78 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Atomic operations usable in machine independent code */
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#ifndef _LINUX_ATOMIC_H
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#define _LINUX_ATOMIC_H
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#include <linux/types.h>
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#include <asm/atomic.h>
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#include <asm/barrier.h>
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/*
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* Relaxed variants of xchg, cmpxchg and some atomic operations.
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*
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* We support four variants:
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*
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* - Fully ordered: The default implementation, no suffix required.
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* - Acquire: Provides ACQUIRE semantics, _acquire suffix.
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* - Release: Provides RELEASE semantics, _release suffix.
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* - Relaxed: No ordering guarantees, _relaxed suffix.
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*
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* For compound atomics performing both a load and a store, ACQUIRE
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* semantics apply only to the load and RELEASE semantics only to the
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* store portion of the operation. Note that a failed cmpxchg_acquire
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* does -not- imply any memory ordering constraints.
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*
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* See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
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*/
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/*
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* The idea here is to build acquire/release variants by adding explicit
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* barriers on top of the relaxed variant. In the case where the relaxed
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* variant is already fully ordered, no additional barriers are needed.
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*
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* If an architecture overrides __atomic_acquire_fence() it will probably
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* want to define smp_mb__after_spinlock().
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*/
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#ifndef __atomic_acquire_fence
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#define __atomic_acquire_fence smp_mb__after_atomic
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#endif
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#ifndef __atomic_release_fence
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#define __atomic_release_fence smp_mb__before_atomic
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#endif
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#ifndef __atomic_pre_full_fence
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#define __atomic_pre_full_fence smp_mb__before_atomic
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#endif
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#ifndef __atomic_post_full_fence
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#define __atomic_post_full_fence smp_mb__after_atomic
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#endif
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#define __atomic_op_acquire(op, args...) \
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({ \
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typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
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__atomic_acquire_fence(); \
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__ret; \
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})
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#define __atomic_op_release(op, args...) \
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({ \
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__atomic_release_fence(); \
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op##_relaxed(args); \
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})
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#define __atomic_op_fence(op, args...) \
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({ \
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typeof(op##_relaxed(args)) __ret; \
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__atomic_pre_full_fence(); \
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__ret = op##_relaxed(args); \
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__atomic_post_full_fence(); \
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__ret; \
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})
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#include <linux/atomic-fallback.h>
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#include <asm-generic/atomic-long.h>
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#endif /* _LINUX_ATOMIC_H */
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