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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:27:49 +0000 |
| commit | ace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch) | |
| tree | b2d64bc10158fdd5497876388cd68142ca374ed3 /arch/alpha/include/asm/rwonce.h | |
| parent | Initial commit. (diff) | |
| download | linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip | |
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/alpha/include/asm/rwonce.h')
| -rw-r--r-- | arch/alpha/include/asm/rwonce.h | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/arch/alpha/include/asm/rwonce.h b/arch/alpha/include/asm/rwonce.h new file mode 100644 index 0000000000..35542bcf92 --- /dev/null +++ b/arch/alpha/include/asm/rwonce.h @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2019 Google LLC. + */ +#ifndef __ASM_RWONCE_H +#define __ASM_RWONCE_H + +#ifdef CONFIG_SMP + +#include <asm/barrier.h> + +/* + * Alpha is apparently daft enough to reorder address-dependent loads + * on some CPU implementations. Knock some common sense into it with + * a memory barrier in READ_ONCE(). + * + * For the curious, more information about this unusual reordering is + * available in chapter 15 of the "perfbook": + * + * https://kernel.org/pub/linux/kernel/people/paulmck/perfbook/perfbook.html + * + */ +#define __READ_ONCE(x) \ +({ \ + __unqual_scalar_typeof(x) __x = \ + (*(volatile typeof(__x) *)(&(x))); \ + mb(); \ + (typeof(x))__x; \ +}) + +#endif /* CONFIG_SMP */ + +#include <asm-generic/rwonce.h> + +#endif /* __ASM_RWONCE_H */ |