linux/arch/x86/include/asm/preempt.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_PREEMPT_H
#define __ASM_PREEMPT_H

#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <asm/current.h>

#include <linux/static_call_types.h>

/* We use the MSB mostly because its available */
#define PREEMPT_NEED_RESCHED …

/*
 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
 * that a decrement hitting 0 means we can and should reschedule.
 */
#define PREEMPT_ENABLED …

/*
 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
 * that think a non-zero value indicates we cannot preempt.
 */
static __always_inline int preempt_count(void)
{ … }

static __always_inline void preempt_count_set(int pc)
{ … }

/*
 * must be macros to avoid header recursion hell
 */
#define init_task_preempt_count(p) …

#define init_idle_preempt_count(p, cpu) …

/*
 * We fold the NEED_RESCHED bit into the preempt count such that
 * preempt_enable() can decrement and test for needing to reschedule with a
 * single instruction.
 *
 * We invert the actual bit, so that when the decrement hits 0 we know we both
 * need to resched (the bit is cleared) and can resched (no preempt count).
 */

static __always_inline void set_preempt_need_resched(void)
{ … }

static __always_inline void clear_preempt_need_resched(void)
{ … }

static __always_inline bool test_preempt_need_resched(void)
{ … }

/*
 * The various preempt_count add/sub methods
 */

static __always_inline void __preempt_count_add(int val)
{ … }

static __always_inline void __preempt_count_sub(int val)
{ … }

/*
 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
 * a decrement which hits zero means we have no preempt_count and should
 * reschedule.
 */
static __always_inline bool __preempt_count_dec_and_test(void)
{ … }

/*
 * Returns true when we need to resched and can (barring IRQ state).
 */
static __always_inline bool should_resched(int preempt_offset)
{ … }

#ifdef CONFIG_PREEMPTION

extern asmlinkage void preempt_schedule(void);
extern asmlinkage void preempt_schedule_thunk(void);

#define preempt_schedule_dynamic_enabled …
#define preempt_schedule_dynamic_disabled …

extern asmlinkage void preempt_schedule_notrace(void);
extern asmlinkage void preempt_schedule_notrace_thunk(void);

#define preempt_schedule_notrace_dynamic_enabled …
#define preempt_schedule_notrace_dynamic_disabled …

#ifdef CONFIG_PREEMPT_DYNAMIC

DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);

#define __preempt_schedule() …

DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);

#define __preempt_schedule_notrace() …

#else /* PREEMPT_DYNAMIC */

#define __preempt_schedule …

#define __preempt_schedule_notrace …

#endif /* PREEMPT_DYNAMIC */

#endif /* PREEMPTION */

#endif /* __ASM_PREEMPT_H */