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v0.8.1
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Tip revision: 521a547ced6477c54b4b0cc206000406c221b4d6 authored by Linus Torvalds on 18 September 2022, 20:44:14 UTC
Linux 6.0-rc6
Tip revision: 521a547
processor.h
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef __ASM_VDSO_PROCESSOR_H
#define __ASM_VDSO_PROCESSOR_H

#ifndef __ASSEMBLY__

#include <linux/jump_label.h>
#include <asm/barrier.h>
#include <asm/hwcap.h>

static inline void cpu_relax(void)
{
	if (!static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_ZIHINTPAUSE])) {
#ifdef __riscv_muldiv
		int dummy;
		/* In lieu of a halt instruction, induce a long-latency stall. */
		__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
#endif
	} else {
		/*
		 * Reduce instruction retirement.
		 * This assumes the PC changes.
		 */
#ifdef __riscv_zihintpause
		__asm__ __volatile__ ("pause");
#else
		/* Encoding of the pause instruction */
		__asm__ __volatile__ (".4byte 0x100000F");
#endif
	}
	barrier();
}

#endif /* __ASSEMBLY__ */

#endif /* __ASM_VDSO_PROCESSOR_H */
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