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

  /*
   * Sleepable Read-Copy Update mechanism for mutual exclusion,
   *	tiny variant.
   *

   * Copyright (C) IBM Corporation, 2017
   *

   * Author: Paul McKenney <paulmck@linux.ibm.com>

   */
  
  #ifndef _LINUX_SRCU_TINY_H
  #define _LINUX_SRCU_TINY_H
  
  #include <linux/swait.h>
  
  struct srcu_struct {

  	short srcu_lock_nesting[2];	/* srcu_read_lock() nesting depth. */
  	short srcu_idx;			/* Current reader array element. */
  	u8 srcu_gp_running;		/* GP workqueue running? */
  	u8 srcu_gp_waiting;		/* GP waiting for readers? */

  	struct swait_queue_head srcu_wq;
  					/* Last srcu_read_unlock() wakes GP. */

  	struct rcu_head *srcu_cb_head;	/* Pending callbacks: Head. */
  	struct rcu_head **srcu_cb_tail;	/* Pending callbacks: Tail. */

  	struct work_struct srcu_work;	/* For driving grace periods. */
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	struct lockdep_map dep_map;
  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  };
  
  void srcu_drive_gp(struct work_struct *wp);

  #define __SRCU_STRUCT_INIT(name, __ignored)				\

  {									\
  	.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq),	\

  	.srcu_cb_tail = &name.srcu_cb_head,				\

  	.srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp),	\
  	__SRCU_DEP_MAP_INIT(name)					\
  }
  
  /*
   * This odd _STATIC_ arrangement is needed for API compatibility with
   * Tree SRCU, which needs some per-CPU data.
   */
  #define DEFINE_SRCU(name) \

  	struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)

  #define DEFINE_STATIC_SRCU(name) \

  	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)

  void synchronize_srcu(struct srcu_struct *ssp);

  /*
   * Counts the new reader in the appropriate per-CPU element of the
   * srcu_struct.  Can be invoked from irq/bh handlers, but the matching
   * __srcu_read_unlock() must be in the same handler instance.  Returns an
   * index that must be passed to the matching srcu_read_unlock().
   */

  static inline int __srcu_read_lock(struct srcu_struct *ssp)

  {
  	int idx;

  	idx = READ_ONCE(ssp->srcu_idx);
  	WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1);

  	return idx;
  }

  static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)

  {

  	synchronize_srcu(ssp);

  }

  static inline void srcu_barrier(struct srcu_struct *ssp)

  {

  	synchronize_srcu(ssp);

  }

  /* Defined here to avoid size increase for non-torture kernels. */

  static inline void srcu_torture_stats_print(struct srcu_struct *ssp,

  					    char *tt, char *tf)
  {
  	int idx;

  	idx = READ_ONCE(ssp->srcu_idx) & 0x1;

  	pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)
  ",
  		 tt, tf, idx,

  		 READ_ONCE(ssp->srcu_lock_nesting[!idx]),
  		 READ_ONCE(ssp->srcu_lock_nesting[idx]));

  }

  #endif