/*
   * Sleepable Read-Copy Update mechanism for mutual exclusion
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
   *
   * Copyright (C) IBM Corporation, 2006
   * Copyright (C) Fujitsu, 2012
   *
   * Author: Paul McKenney <paulmck@us.ibm.com>
   *	   Lai Jiangshan <laijs@cn.fujitsu.com>
   *
   * For detailed explanation of Read-Copy Update mechanism see -
   * 		Documentation/RCU/ *.txt
   *
   */
  
  #ifndef _LINUX_SRCU_H
  #define _LINUX_SRCU_H
  
  #include <linux/mutex.h>
  #include <linux/rcupdate.h>
  #include <linux/workqueue.h>
  
  struct srcu_struct_array {
  	unsigned long c[2];
  	unsigned long seq[2];
  };
  
  struct rcu_batch {
  	struct rcu_head *head, **tail;
  };
  
  #define RCU_BATCH_INIT(name) { NULL, &(name.head) }
  
  struct srcu_struct {
  	unsigned completed;
  	struct srcu_struct_array __percpu *per_cpu_ref;
  	spinlock_t queue_lock; /* protect ->batch_queue, ->running */
  	bool running;
  	/* callbacks just queued */
  	struct rcu_batch batch_queue;
  	/* callbacks try to do the first check_zero */
  	struct rcu_batch batch_check0;
  	/* callbacks done with the first check_zero and the flip */
  	struct rcu_batch batch_check1;
  	struct rcu_batch batch_done;
  	struct delayed_work work;
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	struct lockdep_map dep_map;
  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  };
  
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  
  int __init_srcu_struct(struct srcu_struct *sp, const char *name,
  		       struct lock_class_key *key);
  
  #define init_srcu_struct(sp) \
  ({ \
  	static struct lock_class_key __srcu_key; \
  	\
  	__init_srcu_struct((sp), #sp, &__srcu_key); \
  })
  
  #define __SRCU_DEP_MAP_INIT(srcu_name)	.dep_map = { .name = #srcu_name },
  #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  
  int init_srcu_struct(struct srcu_struct *sp);
  
  #define __SRCU_DEP_MAP_INIT(srcu_name)
  #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  
  void process_srcu(struct work_struct *work);
  
  #define __SRCU_STRUCT_INIT(name)					\
  	{								\
  		.completed = -300,					\
  		.per_cpu_ref = &name##_srcu_array,			\
  		.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock),	\
  		.running = false,					\
  		.batch_queue = RCU_BATCH_INIT(name.batch_queue),	\
  		.batch_check0 = RCU_BATCH_INIT(name.batch_check0),	\
  		.batch_check1 = RCU_BATCH_INIT(name.batch_check1),	\
  		.batch_done = RCU_BATCH_INIT(name.batch_done),		\
  		.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
  		__SRCU_DEP_MAP_INIT(name)				\
  	}
  
  /*
   * define and init a srcu struct at build time.
   * dont't call init_srcu_struct() nor cleanup_srcu_struct() on it.
   */
  #define DEFINE_SRCU(name)						\
  	static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
  	struct srcu_struct name = __SRCU_STRUCT_INIT(name);
  
  #define DEFINE_STATIC_SRCU(name)					\
  	static DEFINE_PER_CPU(struct srcu_struct_array, name##_srcu_array);\
  	static struct srcu_struct name = __SRCU_STRUCT_INIT(name);
  
  /**
   * call_srcu() - Queue a callback for invocation after an SRCU grace period
   * @sp: srcu_struct in queue the callback
   * @head: structure to be used for queueing the SRCU callback.
   * @func: function to be invoked after the SRCU grace period
   *
   * The callback function will be invoked some time after a full SRCU
   * grace period elapses, in other words after all pre-existing SRCU
   * read-side critical sections have completed.  However, the callback
   * function might well execute concurrently with other SRCU read-side
   * critical sections that started after call_srcu() was invoked.  SRCU
   * read-side critical sections are delimited by srcu_read_lock() and
   * srcu_read_unlock(), and may be nested.
   *
   * The callback will be invoked from process context, but must nevertheless
   * be fast and must not block.
   */
  void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
  		void (*func)(struct rcu_head *head));
  
  void cleanup_srcu_struct(struct srcu_struct *sp);
  int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
  void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
  void synchronize_srcu(struct srcu_struct *sp);
  void synchronize_srcu_expedited(struct srcu_struct *sp);
  long srcu_batches_completed(struct srcu_struct *sp);
  void srcu_barrier(struct srcu_struct *sp);
  
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  
  /**
   * srcu_read_lock_held - might we be in SRCU read-side critical section?
   *
   * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
   * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
   * this assumes we are in an SRCU read-side critical section unless it can
   * prove otherwise.
   *
   * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
   * and while lockdep is disabled.
   *
   * Note that SRCU is based on its own statemachine and it doesn't
   * relies on normal RCU, it can be called from the CPU which
   * is in the idle loop from an RCU point of view or offline.
   */
  static inline int srcu_read_lock_held(struct srcu_struct *sp)
  {
  	if (!debug_lockdep_rcu_enabled())
  		return 1;
  	return lock_is_held(&sp->dep_map);
  }
  
  #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  
  static inline int srcu_read_lock_held(struct srcu_struct *sp)
  {
  	return 1;
  }
  
  #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
  
  /**
   * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
   * @p: the pointer to fetch and protect for later dereferencing
   * @sp: pointer to the srcu_struct, which is used to check that we
   *	really are in an SRCU read-side critical section.
   * @c: condition to check for update-side use
   *
   * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
   * critical section will result in an RCU-lockdep splat, unless @c evaluates
   * to 1.  The @c argument will normally be a logical expression containing
   * lockdep_is_held() calls.
   */
  #define srcu_dereference_check(p, sp, c) \
  	__rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)
  
  /**
   * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
   * @p: the pointer to fetch and protect for later dereferencing
   * @sp: pointer to the srcu_struct, which is used to check that we
   *	really are in an SRCU read-side critical section.
   *
   * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
   * is enabled, invoking this outside of an RCU read-side critical
   * section will result in an RCU-lockdep splat.
   */
  #define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0)
  
  /**
   * srcu_read_lock - register a new reader for an SRCU-protected structure.
   * @sp: srcu_struct in which to register the new reader.
   *
   * Enter an SRCU read-side critical section.  Note that SRCU read-side
   * critical sections may be nested.  However, it is illegal to
   * call anything that waits on an SRCU grace period for the same
   * srcu_struct, whether directly or indirectly.  Please note that
   * one way to indirectly wait on an SRCU grace period is to acquire
   * a mutex that is held elsewhere while calling synchronize_srcu() or
   * synchronize_srcu_expedited().
   *
   * Note that srcu_read_lock() and the matching srcu_read_unlock() must
   * occur in the same context, for example, it is illegal to invoke
   * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
   * was invoked in process context.
   */
  static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp)
  {
  	int retval = __srcu_read_lock(sp);
  
  	rcu_lock_acquire(&(sp)->dep_map);
  	return retval;
  }
  
  /**
   * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
   * @sp: srcu_struct in which to unregister the old reader.
   * @idx: return value from corresponding srcu_read_lock().
   *
   * Exit an SRCU read-side critical section.
   */
  static inline void srcu_read_unlock(struct srcu_struct *sp, int idx)
  	__releases(sp)
  {
  	rcu_lock_release(&(sp)->dep_map);
  	__srcu_read_unlock(sp, idx);
  }
  
  /**
   * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
   *
   * Converts the preceding srcu_read_unlock into a two-way memory barrier.
   *
   * Call this after srcu_read_unlock, to guarantee that all memory operations
   * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
   * the preceding srcu_read_unlock.
   */
  static inline void smp_mb__after_srcu_read_unlock(void)
  {
  	/* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
  }
  
  #endif