Linux kernel mirror (for testing)
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1/* SPDX-License-Identifier: GPL-2.0-only */
2#ifndef __ASM_VDSO_PROCESSOR_H
3#define __ASM_VDSO_PROCESSOR_H
4
5#ifndef __ASSEMBLY__
6
7#include <linux/jump_label.h>
8#include <asm/barrier.h>
9#include <asm/hwcap.h>
10
11static inline void cpu_relax(void)
12{
13 if (!static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_ZIHINTPAUSE])) {
14#ifdef __riscv_muldiv
15 int dummy;
16 /* In lieu of a halt instruction, induce a long-latency stall. */
17 __asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
18#endif
19 } else {
20 /*
21 * Reduce instruction retirement.
22 * This assumes the PC changes.
23 */
24#ifdef __riscv_zihintpause
25 __asm__ __volatile__ ("pause");
26#else
27 /* Encoding of the pause instruction */
28 __asm__ __volatile__ (".4byte 0x100000F");
29#endif
30 }
31 barrier();
32}
33
34#endif /* __ASSEMBLY__ */
35
36#endif /* __ASM_VDSO_PROCESSOR_H */