Perform an exclusive load, which atomically loads a word and arms the exclusive monitor to enable wfet()/wfe() accelerated polling. https://developer.arm.com/documentation/dht0008/a/arm-synchronization-primitives/exclusive-accesses/exclusive-monitors Signed-off-by: Haris Okanovic <harisokn@xxxxxxxxxx> --- arch/arm64/include/asm/readex.h | 46 +++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 arch/arm64/include/asm/readex.h diff --git a/arch/arm64/include/asm/readex.h b/arch/arm64/include/asm/readex.h new file mode 100644 index 000000000000..51963c3107e1 --- /dev/null +++ b/arch/arm64/include/asm/readex.h @@ -0,0 +1,46 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Based on arch/arm64/include/asm/rwonce.h + * + * Copyright (C) 2020 Google LLC. + * Copyright (C) 2024 Amazon.com, Inc. or its affiliates. + */ + +#ifndef __ASM_READEX_H +#define __ASM_READEX_H + +#define __LOAD_EX(sfx, regs...) "ldaxr" #sfx "\t" #regs + +#define __READ_ONCE_EX(x) \ +({ \ + typeof(&(x)) __x = &(x); \ + int atomic = 1; \ + union { __unqual_scalar_typeof(*__x) __val; char __c[1]; } __u; \ + switch (sizeof(x)) { \ + case 1: \ + asm volatile(__LOAD_EX(b, %w0, %1) \ + : "=r" (*(__u8 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 2: \ + asm volatile(__LOAD_EX(h, %w0, %1) \ + : "=r" (*(__u16 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 4: \ + asm volatile(__LOAD_EX(, %w0, %1) \ + : "=r" (*(__u32 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + case 8: \ + asm volatile(__LOAD_EX(, %0, %1) \ + : "=r" (*(__u64 *)__u.__c) \ + : "Q" (*__x) : "memory"); \ + break; \ + default: \ + atomic = 0; \ + } \ + atomic ? (typeof(*__x))__u.__val : (*(volatile typeof(__x))__x);\ +}) + +#endif -- 2.34.1
