path: root/kernel/rcutiny_plugin.h

/*
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (c) 2010 Linaro
 *
 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

#include <linux/kthread.h>
#include <linux/module.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(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
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

#ifdef CONFIG_RCU_TRACE

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 = rcp->jiffies_stall;
	if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
		       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
		       jiffies - rcp->gp_start, rcp->qlen);
		dump_stack();
	}
	if (*rcp->curtail && ULONG_CMP_GE(j, js))
		rcp->jiffies_stall = jiffies +
			3 * rcu_jiffies_till_stall_check() + 3;
	else if (ULONG_CMP_GE(j, js))
		rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}

static void check_cpu_stall_preempt(void);

#endif /* #ifdef CONFIG_RCU_TRACE */

static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
{
#ifdef CONFIG_RCU_TRACE
	rcp->ticks_this_gp = 0;
	rcp->gp_start = jiffies;
	rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
#endif /* #ifdef CONFIG_RCU_TRACE */
}

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

#ifdef CONFIG_TINY_PREEMPT_RCU

#include <linux/delay.h>

/* Global control variables for preemptible RCU. */
struct rcu_preempt_ctrlblk {
	struct rcu_ctrlblk rcb;	/* curtail: ->next ptr of last CB for GP. */
	struct rcu_head **nexttail;
				/* Tasks blocked in a preemptible RCU */
				/*  read-side critical section while an */
				/*  preemptible-RCU grace period is in */
				/*  progress must wait for a later grace */
				/*  period.  This pointer points to the */
				/*  ->next pointer of the last task that */
				/*  must wait for a later grace period, or */
				/*  to &->rcb.rcucblist if there is no */
				/*  such task. */
	struct list_head blkd_tasks;
				/* Tasks blocked in RCU read-side critical */
				/*  section.  Tasks are placed at the head */
				/*  of this list and age towards the tail. */
	struct list_head *gp_tasks;
				/* Pointer to the first task blocking the */
				/*  current grace period, or NULL if there */
				/*  is no such task. */
	struct list_head *exp_tasks;
				/* Pointer to first task blocking the */
				/*  current expedited grace period, or NULL */
				/*  if there is no such task.  If there */
				/*  is no current expedited grace period, */
				/*  then there cannot be any such task. */
#ifdef CONFIG_RCU_BOOST
	struct list_head *boost_tasks;
				/* Pointer to first task that needs to be */
				/*  priority-boosted, or NULL if no priority */
				/*  boosting is needed.  If there is no */
				/*  current or expedited grace p