/*

   * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition

   * Internal non-public definitions that provide either classic

   * or preemptible semantics.

   *
   * 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, you can access it online at
   * http://www.gnu.org/licenses/gpl-2.0.html.

   *

   * Copyright (c) 2010 Linaro

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

  #include <linux/kthread.h>

  #include <linux/init.h>

  #include <linux/debugfs.h>
  #include <linux/seq_file.h>

  /* Global control variables for rcupdate callback mechanism. */
  struct rcu_ctrlblk {
  	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
  	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
  	struct rcu_head **curtail;	/* ->next pointer of last CB. */

  	RCU_TRACE(long qlen);		/* Number of pending CBs. */

  	RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
  	RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
  	RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */

  	RCU_TRACE(const char *name);	/* Name of RCU type. */

  };
  
  /* Definition for rcupdate control block. */
  static struct rcu_ctrlblk rcu_sched_ctrlblk = {
  	.donetail	= &rcu_sched_ctrlblk.rcucblist,
  	.curtail	= &rcu_sched_ctrlblk.rcucblist,

  	RCU_TRACE(.name = "rcu_sched")

  };
  
  static struct rcu_ctrlblk rcu_bh_ctrlblk = {
  	.donetail	= &rcu_bh_ctrlblk.rcucblist,
  	.curtail	= &rcu_bh_ctrlblk.rcucblist,

  	RCU_TRACE(.name = "rcu_bh")

  };
  
  #ifdef CONFIG_DEBUG_LOCK_ALLOC

  #include <linux/kernel_stat.h>

  int rcu_scheduler_active __read_mostly;
  EXPORT_SYMBOL_GPL(rcu_scheduler_active);

  
  /*
   * During boot, we forgive RCU lockdep issues.  After this function is
   * invoked, we start taking RCU lockdep issues seriously.
   */

  void __init rcu_scheduler_starting(void)

  {
  	WARN_ON(nr_context_switches() > 0);
  	rcu_scheduler_active = 1;
  }
  
  #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

  #ifdef CONFIG_RCU_TRACE

  static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
  {
  	unsigned long flags;

  	local_irq_save(flags);

  	rcp->qlen -= n;

  	local_irq_restore(flags);

  }
  
  /*
   * Dump statistics for TINY_RCU, such as they are.
   */
  static int show_tiny_stats(struct seq_file *m, void *unused)
  {

  	seq_printf(m, "rcu_sched: qlen: %ld
  ", rcu_sched_ctrlblk.qlen);
  	seq_printf(m, "rcu_bh: qlen: %ld
  ", rcu_bh_ctrlblk.qlen);
  	return 0;
  }
  
  static int show_tiny_stats_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, show_tiny_stats, NULL);
  }
  
  static const struct file_operations show_tiny_stats_fops = {
  	.owner = THIS_MODULE,
  	.open = show_tiny_stats_open,
  	.read = seq_read,
  	.llseek = seq_lseek,
  	.release = single_release,
  };
  
  static struct dentry *rcudir;
  
  static int __init rcutiny_trace_init(void)
  {
  	struct dentry *retval;
  
  	rcudir = debugfs_create_dir("rcu", NULL);
  	if (!rcudir)
  		goto free_out;
  	retval = debugfs_create_file("rcudata", 0444, rcudir,
  				     NULL, &show_tiny_stats_fops);
  	if (!retval)
  		goto free_out;
  	return 0;
  free_out:
  	debugfs_remove_recursive(rcudir);
  	return 1;
  }

  device_initcall(rcutiny_trace_init);

  static void check_cpu_stall(struct rcu_ctrlblk *rcp)
  {
  	unsigned long j;
  	unsigned long js;
  
  	if (rcu_cpu_stall_suppress)
  		return;
  	rcp->ticks_this_gp++;
  	j = jiffies;

  	js = READ_ONCE(rcp->jiffies_stall);

  	if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {

  		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)
  ",

  		       rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE,

  		       jiffies - rcp->gp_start, rcp->qlen);
  		dump_stack();

  		WRITE_ONCE(rcp->jiffies_stall,
  			   jiffies + 3 * rcu_jiffies_till_stall_check() + 3);

  	} else if (ULONG_CMP_GE(j, js)) {

  		WRITE_ONCE(rcp->jiffies_stall,
  			   jiffies + rcu_jiffies_till_stall_check());

  	}

  }

  static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
  {

  	rcp->ticks_this_gp = 0;
  	rcp->gp_start = jiffies;

  	WRITE_ONCE(rcp->jiffies_stall,
  		   jiffies + rcu_jiffies_till_stall_check());

  }
  
  static void check_cpu_stalls(void)
  {
  	RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
  	RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
  }

  
  #endif /* #ifdef CONFIG_RCU_TRACE */