/*
   * 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
   *
   * Author: Paul McKenney <paulmck@us.ibm.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>

  struct srcu_struct_array {
  	int c[2];
  };
  
  struct srcu_struct {
  	int completed;

  	struct srcu_struct_array __percpu *per_cpu_ref;

  	struct mutex mutex;

  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  	struct lockdep_map dep_map;
  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

  };
  
  #ifndef CONFIG_PREEMPT
  #define srcu_barrier() barrier()
  #else /* #ifndef CONFIG_PREEMPT */
  #define srcu_barrier()
  #endif /* #else #ifndef CONFIG_PREEMPT */

  #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); \
  })

  #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

  int init_srcu_struct(struct srcu_struct *sp);

  #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

  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);

  #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 if the CPU is in the idle loop from an RCU point of view
   * (ie: that we are in the section between rcu_idle_enter() and
   * rcu_idle_exit()) then srcu_read_lock_held() returns false even if
   * the CPU did an srcu_read_lock().  The reason for this is that RCU
   * ignores CPUs that are in such a section, considering these as in
   * extended quiescent state, so such a CPU is effectively never in an
   * RCU read-side critical section regardless of what RCU primitives it
   * invokes.  This state of affairs is required --- we need to keep an
   * RCU-free window in idle where the CPU may possibly enter into low
   * power mode. This way we can notice an extended quiescent state to
   * other CPUs that started a grace period. Otherwise we would delay any
   * grace period as long as we run in the idle task.

   */
  static inline int srcu_read_lock_held(struct srcu_struct *sp)
  {

  	if (rcu_is_cpu_idle())
  		return 0;

  	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);
  }

  /**
   * srcu_read_lock_raw - 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.  Similar to srcu_read_lock(),
   * but avoids the RCU-lockdep checking.  This means that it is legal to
   * use srcu_read_lock_raw() in one context, for example, in an exception
   * handler, and then have the matching srcu_read_unlock_raw() in another
   * context, for example in the task that took the exception.
   *
   * However, the entire SRCU read-side critical section must reside within a
   * single task.  For example, beware of using srcu_read_lock_raw() in
   * a device interrupt handler and srcu_read_unlock() in the interrupted
   * task:  This will not work if interrupts are threaded.
   */
  static inline int srcu_read_lock_raw(struct srcu_struct *sp)
  {
  	unsigned long flags;
  	int ret;
  
  	local_irq_save(flags);
  	ret =  __srcu_read_lock(sp);
  	local_irq_restore(flags);
  	return ret;
  }
  
  /**
   * srcu_read_unlock_raw - unregister reader from an SRCU-protected structure.
   * @sp: srcu_struct in which to unregister the old reader.
   * @idx: return value from corresponding srcu_read_lock_raw().
   *
   * Exit an SRCU read-side critical section without lockdep-RCU checking.
   * See srcu_read_lock_raw() for more details.
   */
  static inline void srcu_read_unlock_raw(struct srcu_struct *sp, int idx)
  {
  	unsigned long flags;
  
  	local_irq_save(flags);
  	__srcu_read_unlock(sp, idx);
  	local_irq_restore(flags);
  }

  #endif