cregit-Linux how code gets into the kernel

Release 4.18 arch/arm64/include/asm/simd.h

/*
 * Copyright (C) 2017 Linaro Ltd. <ard.biesheuvel@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 */

#ifndef __ASM_SIMD_H

#define __ASM_SIMD_H

#include <linux/compiler.h>
#include <linux/irqflags.h>
#include <linux/percpu.h>
#include <linux/preempt.h>
#include <linux/types.h>

#ifdef CONFIG_KERNEL_MODE_NEON

DECLARE_PER_CPU(bool, kernel_neon_busy);

/*
 * may_use_simd - whether it is allowable at this time to issue SIMD
 *                instructions or access the SIMD register file
 *
 * Callers must not assume that the result remains true beyond the next
 * preempt_enable() or return from softirq context.
 */

static __must_check inline bool may_use_simd(void) { /* * kernel_neon_busy is only set while preemption is disabled, * and is clear whenever preemption is enabled. Since * this_cpu_read() is atomic w.r.t. preemption, kernel_neon_busy * cannot change under our feet -- if it's set we cannot be * migrated, and if it's clear we cannot be migrated to a CPU * where it is set. */ return !in_irq() && !irqs_disabled() && !in_nmi() && !this_cpu_read(kernel_neon_busy); }

Contributors

PersonTokensPropCommitsCommitProp
Dave P Martin2893.33%266.67%
Yandong Zhao26.67%133.33%
Total30100.00%3100.00%

#else /* ! CONFIG_KERNEL_MODE_NEON */
static __must_check inline bool may_use_simd(void) { return false; }

Contributors

PersonTokensPropCommitsCommitProp
Ard Biesheuvel1292.31%150.00%
Dave P Martin17.69%150.00%
Total13100.00%2100.00%

#endif /* ! CONFIG_KERNEL_MODE_NEON */ #endif

Overall Contributors

PersonTokensPropCommitsCommitProp
Dave P Martin5869.05%250.00%
Ard Biesheuvel2428.57%125.00%
Yandong Zhao22.38%125.00%
Total84100.00%4100.00%
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