/*
   * 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 IBM Corporation, 2001

   *
   * Authors: Dipankar Sarma <dipankar@in.ibm.com>
   *	    Manfred Spraul <manfred@colorfullife.com>

   *

   * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
   * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
   * Papers:
   * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
   * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
   *
   * For detailed explanation of Read-Copy Update mechanism see -

   *		http://lse.sourceforge.net/locking/rcupdate.html

   *
   */
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/spinlock.h>
  #include <linux/smp.h>
  #include <linux/interrupt.h>
  #include <linux/sched.h>
  #include <asm/atomic.h>
  #include <linux/bitops.h>

  #include <linux/percpu.h>
  #include <linux/notifier.h>

  #include <linux/cpu.h>

  #include <linux/mutex.h>

  #include <linux/module.h>

  #include <linux/kernel_stat.h>

  #include <linux/hardirq.h>

  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  static struct lock_class_key rcu_lock_key;
  struct lockdep_map rcu_lock_map =
  	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
  EXPORT_SYMBOL_GPL(rcu_lock_map);

  
  static struct lock_class_key rcu_bh_lock_key;
  struct lockdep_map rcu_bh_lock_map =
  	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
  EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
  
  static struct lock_class_key rcu_sched_lock_key;
  struct lockdep_map rcu_sched_lock_map =
  	STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
  EXPORT_SYMBOL_GPL(rcu_sched_lock_map);

  #endif

  int rcu_scheduler_active __read_mostly;

  EXPORT_SYMBOL_GPL(rcu_scheduler_active);

  #ifdef CONFIG_DEBUG_LOCK_ALLOC

  int debug_lockdep_rcu_enabled(void)
  {
  	return rcu_scheduler_active && debug_locks &&
  	       current->lockdep_recursion == 0;
  }
  EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);

  /**
   * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
   *
   * Check for bottom half being disabled, which covers both the
   * CONFIG_PROVE_RCU and not cases.  Note that if someone uses
   * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
   * will show the situation.
   *
   * Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
   */
  int rcu_read_lock_bh_held(void)
  {
  	if (!debug_lockdep_rcu_enabled())
  		return 1;
  	return in_softirq();
  }
  EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
  
  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

  /*
   * This function is invoked towards the end of the scheduler's initialization
   * process.  Before this is called, the idle task might contain
   * RCU read-side critical sections (during which time, this idle
   * task is booting the system).  After this function is called, the
   * idle tasks are prohibited from containing RCU read-side critical
   * sections.
   */
  void rcu_scheduler_starting(void)
  {
  	WARN_ON(num_online_cpus() != 1);
  	WARN_ON(nr_context_switches() > 0);
  	rcu_scheduler_active = 1;
  }

  /*
   * Awaken the corresponding synchronize_rcu() instance now that a
   * grace period has elapsed.
   */

  void wakeme_after_rcu(struct rcu_head  *head)

  {

  	struct rcu_synchronize *rcu;
  
  	rcu = container_of(head, struct rcu_synchronize, head);
  	complete(&rcu->completion);

  }

  
  #ifdef CONFIG_PROVE_RCU
  /*
   * wrapper function to avoid #include problems.
   */
  int rcu_my_thread_group_empty(void)
  {
  	return thread_group_empty(current);
  }
  EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
  #endif /* #ifdef CONFIG_PROVE_RCU */