/* SPDX-License-Identifier: GPL-2.0 */

  #ifndef __LINUX_PREEMPT_H
  #define __LINUX_PREEMPT_H
  
  /*
   * include/linux/preempt.h - macros for accessing and manipulating
   * preempt_count (used for kernel preemption, interrupt count, etc.)
   */

  #include <linux/linkage.h>

  #include <linux/list.h>

  /*

   * We put the hardirq and softirq counter into the preemption
   * counter. The bitmask has the following meaning:
   *
   * - bits 0-7 are the preemption count (max preemption depth: 256)
   * - bits 8-15 are the softirq count (max # of softirqs: 256)
   *
   * The hardirq count could in theory be the same as the number of
   * interrupts in the system, but we run all interrupt handlers with
   * interrupts disabled, so we cannot have nesting interrupts. Though
   * there are a few palaeontologic drivers which reenable interrupts in
   * the handler, so we need more than one bit here.
   *

   *         PREEMPT_MASK:	0x000000ff
   *         SOFTIRQ_MASK:	0x0000ff00
   *         HARDIRQ_MASK:	0x000f0000
   *             NMI_MASK:	0x00100000

   * PREEMPT_NEED_RESCHED:	0x80000000

   */
  #define PREEMPT_BITS	8
  #define SOFTIRQ_BITS	8
  #define HARDIRQ_BITS	4
  #define NMI_BITS	1
  
  #define PREEMPT_SHIFT	0
  #define SOFTIRQ_SHIFT	(PREEMPT_SHIFT + PREEMPT_BITS)
  #define HARDIRQ_SHIFT	(SOFTIRQ_SHIFT + SOFTIRQ_BITS)
  #define NMI_SHIFT	(HARDIRQ_SHIFT + HARDIRQ_BITS)
  
  #define __IRQ_MASK(x)	((1UL << (x))-1)
  
  #define PREEMPT_MASK	(__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT)
  #define SOFTIRQ_MASK	(__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
  #define HARDIRQ_MASK	(__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)
  #define NMI_MASK	(__IRQ_MASK(NMI_BITS)     << NMI_SHIFT)
  
  #define PREEMPT_OFFSET	(1UL << PREEMPT_SHIFT)
  #define SOFTIRQ_OFFSET	(1UL << SOFTIRQ_SHIFT)
  #define HARDIRQ_OFFSET	(1UL << HARDIRQ_SHIFT)
  #define NMI_OFFSET	(1UL << NMI_SHIFT)
  
  #define SOFTIRQ_DISABLE_OFFSET	(2 * SOFTIRQ_OFFSET)

  /* We use the MSB mostly because its available */
  #define PREEMPT_NEED_RESCHED	0x80000000

  #define PREEMPT_DISABLED	(PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)
  
  /*
   * Disable preemption until the scheduler is running -- use an unconditional
   * value so that it also works on !PREEMPT_COUNT kernels.
   *
   * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count().
   */
  #define INIT_PREEMPT_COUNT	PREEMPT_OFFSET
  
  /*
   * Initial preempt_count value; reflects the preempt_count schedule invariant
   * which states that during context switches:
   *
   *    preempt_count() == 2*PREEMPT_DISABLE_OFFSET
   *
   * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels.
   * Note: See finish_task_switch().
   */
  #define FORK_PREEMPT_COUNT	(2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED)

  /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */
  #include <asm/preempt.h>

  #define hardirq_count()	(preempt_count() & HARDIRQ_MASK)
  #define softirq_count()	(preempt_count() & SOFTIRQ_MASK)
  #define irq_count()	(preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \
  				 | NMI_MASK))
  
  /*
   * Are we doing bottom half or hardware interrupt processing?

   *
   * in_irq()       - We're in (hard) IRQ context
   * in_softirq()   - We have BH disabled, or are processing softirqs
   * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled
   * in_serving_softirq() - We're in softirq context
   * in_nmi()       - We're in NMI context
   * in_task()	  - We're in task context
   *
   * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really
   *       should not be used in new code.

   */
  #define in_irq()		(hardirq_count())
  #define in_softirq()		(softirq_count())
  #define in_interrupt()		(irq_count())
  #define in_serving_softirq()	(softirq_count() & SOFTIRQ_OFFSET)

  #define in_nmi()		(preempt_count() & NMI_MASK)
  #define in_task()		(!(preempt_count() & \
  				   (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))

  /*
   * The preempt_count offset after preempt_disable();
   */

  #if defined(CONFIG_PREEMPT_COUNT)

  # define PREEMPT_DISABLE_OFFSET	PREEMPT_OFFSET

  #else

  # define PREEMPT_DISABLE_OFFSET	0

  #endif
  
  /*

   * The preempt_count offset after spin_lock()
   */
  #define PREEMPT_LOCK_OFFSET	PREEMPT_DISABLE_OFFSET
  
  /*

   * The preempt_count offset needed for things like:
   *
   *  spin_lock_bh()
   *
   * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and
   * softirqs, such that unlock sequences of:
   *
   *  spin_unlock();
   *  local_bh_enable();
   *
   * Work as expected.
   */

  #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET)

  
  /*
   * Are we running in atomic context?  WARNING: this macro cannot
   * always detect atomic context; in particular, it cannot know about
   * held spinlocks in non-preemptible kernels.  Thus it should not be
   * used in the general case to determine whether sleeping is possible.
   * Do not use in_atomic() in driver code.
   */

  #define in_atomic()	(preempt_count() != 0)

  
  /*
   * Check whether we were atomic before we did preempt_disable():

   * (used by the scheduler)

   */

  #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)

  #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)

  extern void preempt_count_add(int val);
  extern void preempt_count_sub(int val);

  #define preempt_count_dec_and_test() \
  	({ preempt_count_sub(1); should_resched(0); })

  #else

  #define preempt_count_add(val)	__preempt_count_add(val)
  #define preempt_count_sub(val)	__preempt_count_sub(val)
  #define preempt_count_dec_and_test() __preempt_count_dec_and_test()

  #endif

  #define __preempt_count_inc() __preempt_count_add(1)
  #define __preempt_count_dec() __preempt_count_sub(1)

  #define preempt_count_inc() preempt_count_add(1)
  #define preempt_count_dec() preempt_count_sub(1)

  
  #ifdef CONFIG_PREEMPT_COUNT

  #define preempt_disable() \
  do { \

  	preempt_count_inc(); \

  	barrier(); \
  } while (0)

  #define sched_preempt_enable_no_resched() \

  do { \
  	barrier(); \

  	preempt_count_dec(); \

  } while (0)

  #define preempt_enable_no_resched() sched_preempt_enable_no_resched()

  #define preemptible()	(preempt_count() == 0 && !irqs_disabled())

  #ifdef CONFIG_PREEMPT

  #define preempt_enable() \
  do { \

  	barrier(); \
  	if (unlikely(preempt_count_dec_and_test())) \

  		__preempt_schedule(); \

  } while (0)

  #define preempt_enable_notrace() \
  do { \
  	barrier(); \
  	if (unlikely(__preempt_count_dec_and_test())) \
  		__preempt_schedule_notrace(); \
  } while (0)

  #define preempt_check_resched() \
  do { \

  	if (should_resched(0)) \

  		__preempt_schedule(); \

  } while (0)

  #else /* !CONFIG_PREEMPT */

  #define preempt_enable() \
  do { \
  	barrier(); \
  	preempt_count_dec(); \
  } while (0)

  #define preempt_enable_notrace() \

  do { \
  	barrier(); \

  	__preempt_count_dec(); \

  } while (0)

  #define preempt_check_resched() do { } while (0)
  #endif /* CONFIG_PREEMPT */

  #define preempt_disable_notrace() \

  do { \

  	__preempt_count_inc(); \

  	barrier(); \

  } while (0)

  
  #define preempt_enable_no_resched_notrace() \

  do { \
  	barrier(); \
  	__preempt_count_dec(); \
  } while (0)

  #else /* !CONFIG_PREEMPT_COUNT */

  /*
   * Even if we don't have any preemption, we need preempt disable/enable
   * to be barriers, so that we don't have things like get_user/put_user
   * that can cause faults and scheduling migrate into our preempt-protected
   * region.
   */

  #define preempt_disable()			barrier()

  #define sched_preempt_enable_no_resched()	barrier()

  #define preempt_enable_no_resched()		barrier()
  #define preempt_enable()			barrier()
  #define preempt_check_resched()			do { } while (0)

  
  #define preempt_disable_notrace()		barrier()
  #define preempt_enable_no_resched_notrace()	barrier()
  #define preempt_enable_notrace()		barrier()

  #define preemptible()				0

  #endif /* CONFIG_PREEMPT_COUNT */

  #ifdef MODULE
  /*
   * Modules have no business playing preemption tricks.
   */
  #undef sched_preempt_enable_no_resched
  #undef preempt_enable_no_resched
  #undef preempt_enable_no_resched_notrace
  #undef preempt_check_resched
  #endif

  #define preempt_set_need_resched() \
  do { \
  	set_preempt_need_resched(); \
  } while (0)
  #define preempt_fold_need_resched() \
  do { \
  	if (tif_need_resched()) \
  		set_preempt_need_resched(); \
  } while (0)

  #ifdef CONFIG_PREEMPT_NOTIFIERS
  
  struct preempt_notifier;
  
  /**
   * preempt_ops - notifiers called when a task is preempted and rescheduled
   * @sched_in: we're about to be rescheduled:
   *    notifier: struct preempt_notifier for the task being scheduled
   *    cpu:  cpu we're scheduled on
   * @sched_out: we've just been preempted
   *    notifier: struct preempt_notifier for the task being preempted
   *    next: the task that's kicking us out

   *
   * Please note that sched_in and out are called under different
   * contexts.  sched_out is called with rq lock held and irq disabled
   * while sched_in is called without rq lock and irq enabled.  This
   * difference is intentional and depended upon by its users.

   */
  struct preempt_ops {
  	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
  	void (*sched_out)(struct preempt_notifier *notifier,
  			  struct task_struct *next);
  };
  
  /**
   * preempt_notifier - key for installing preemption notifiers
   * @link: internal use
   * @ops: defines the notifier functions to be called
   *
   * Usually used in conjunction with container_of().
   */
  struct preempt_notifier {
  	struct hlist_node link;
  	struct preempt_ops *ops;
  };

  void preempt_notifier_inc(void);
  void preempt_notifier_dec(void);

  void preempt_notifier_register(struct preempt_notifier *notifier);
  void preempt_notifier_unregister(struct preempt_notifier *notifier);
  
  static inline void preempt_notifier_init(struct preempt_notifier *notifier,
  				     struct preempt_ops *ops)
  {
  	INIT_HLIST_NODE(&notifier->link);
  	notifier->ops = ops;
  }
  
  #endif

  #endif /* __LINUX_PREEMPT_H */