projects / deliverable / lttng-modules.git / blame
| Commit | Line | Data |
|---|---|---|
| 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 */ |