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6657edec MD |
1 | /* SPDX-License-Identifier: GPL-2.0-only |
2 | * | |
3 | * wrapper/barrier.h | |
4 | * | |
5 | * wrapper around asm/barrier.h. | |
6 | * | |
7 | * Copyright (C) 2020 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
8 | */ | |
9 | ||
10 | #ifndef _LTTNG_WRAPPER_BARRIER_H | |
11 | #define _LTTNG_WRAPPER_BARRIER_H | |
12 | ||
13 | #include <linux/version.h> | |
14 | #include <asm/barrier.h> | |
15 | ||
16 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(3,14,0) | |
17 | ||
18 | #define lttng_smp_store_release(x, v) smp_store_release(x, v) | |
19 | #define lttng_smp_load_acquire(x) smp_load_acquire(x) | |
20 | ||
21 | #else | |
22 | ||
23 | /* | |
24 | * Acquire-release semantics act as a one-way permeable barrier when | |
25 | * pairing a store with a release. Use a full memory barrier to emulate | |
26 | * the acquire-release semantic with a stronger barrier on older | |
27 | * kernels. | |
28 | */ | |
29 | ||
30 | #define lttng_smp_store_release(x, v) \ | |
31 | do { \ | |
32 | smp_mb(); \ | |
33 | ACCESS_ONCE(*(x)) = (v); \ | |
34 | } while (0) | |
35 | ||
36 | #define lttng_smp_load_acquire(x) \ | |
37 | ({ \ | |
38 | __typeof__(*(x)) ___ret; \ | |
39 | \ | |
40 | ___ret = ACCESS_ONCE(*(x)); \ | |
41 | smp_mb(); \ | |
42 | ___ret; \ | |
43 | }) | |
44 | ||
45 | #endif | |
46 | ||
47 | #endif /* _LTTNG_WRAPPER_BARRIER_H */ |