Quelle  preempt.h   Sprache: C

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

#include <linux/jump_label.h>
#include <linux/thread_info.h>

#define PREEMPT_NEED_RESCHED BIT(32)
#define PREEMPT_ENABLED (PREEMPT_NEED_RESCHED)

static inline int preempt_count(void)
{
 return READ_ONCE(current_thread_info()->preempt.count);
}

static inline void preempt_count_set(u64 pc)
{
 /* Preserve existing value of PREEMPT_NEED_RESCHED */
 WRITE_ONCE(current_thread_info()->preempt.count, pc);
}

#define init_task_preempt_count(p) do { \
 task_thread_info(p)->preempt_count = FORK_PREEMPT_COUNT; \
} while (0)

#define init_idle_preempt_count(p, cpu) do { \
 task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
} while (0)

static inline void set_preempt_need_resched(void)
{
 current_thread_info()->preempt.need_resched = 0;
}

static inline void clear_preempt_need_resched(void)
{
 current_thread_info()->preempt.need_resched = 1;
}

static inline bool test_preempt_need_resched(void)
{
 return !current_thread_info()->preempt.need_resched;
}

static inline void __preempt_count_add(int val)
{
 u32 pc = READ_ONCE(current_thread_info()->preempt.count);
 pc += val;
 WRITE_ONCE(current_thread_info()->preempt.count, pc);
}

static inline void __preempt_count_sub(int val)
{
 u32 pc = READ_ONCE(current_thread_info()->preempt.count);
 pc -= val;
 WRITE_ONCE(current_thread_info()->preempt.count, pc);
}

static inline bool __preempt_count_dec_and_test(void)
{
 struct thread_info *ti = current_thread_info();
 u64 pc = READ_ONCE(ti->preempt_count);

 /* Update only the count field, leaving need_resched unchanged */
 WRITE_ONCE(ti->preempt.count, --pc);

 /*
 * If we wrote back all zeroes, then we're preemptible and in
 * need of a reschedule. Otherwise, we need to reload the
 * preempt_count in case the need_resched flag was cleared by an
 * interrupt occurring between the non-atomic READ_ONCE/WRITE_ONCE
 * pair.
 */
 return !pc || !READ_ONCE(ti->preempt_count);
}

static inline bool should_resched(int preempt_offset)
{
 u64 pc = READ_ONCE(current_thread_info()->preempt_count);
 return pc == preempt_offset;
}

#ifdef CONFIG_PREEMPTION

void preempt_schedule(void);
void preempt_schedule_notrace(void);

#ifdef CONFIG_PREEMPT_DYNAMIC

DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
void dynamic_preempt_schedule(void);
#define __preempt_schedule()  dynamic_preempt_schedule()
void dynamic_preempt_schedule_notrace(void);
#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace()

#else /* CONFIG_PREEMPT_DYNAMIC */

#define __preempt_schedule()  preempt_schedule()
#define __preempt_schedule_notrace() preempt_schedule_notrace()

#endif /* CONFIG_PREEMPT_DYNAMIC */
#endif /* CONFIG_PREEMPTION */

#endif /* __ASM_PREEMPT_H */