path: root/include/linux/rcupdate.h

/*
 * 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, you can access it online at
 * http://www.gnu.org/licenses/gpl-2.0.html.
 *
 * Copyright IBM Corporation, 2001
 *
 * Author: Dipankar Sarma <dipankar@in.ibm.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
 *
 */

#ifndef __LINUX_RCUPDATE_H
#define __LINUX_RCUPDATE_H

#include <linux/types.h>
#include <linux/cache.h>
#include <linux/spinlock.h>
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#include <linux/lockdep.h>
#include <linux/completion.h>
#include <linux/debugobjects.h>
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/ktime.h>
#include <linux/irqflags.h>

#include <asm/barrier.h>

#ifndef CONFIG_TINY_RCU
extern int rcu_expedited; /* for sysctl */
extern int rcu_normal;    /* also for sysctl */
#endif /* #ifndef CONFIG_TINY_RCU */

#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void)  /* Internal RCU use. */
{
	return true;
}
static inline bool rcu_gp_is_expedited(void)  /* Internal RCU use. */
{
	return false;
}

static inline void rcu_expedite_gp(void)
{
}

static inline void rcu_unexpedite_gp(void)
{
}
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_normal(void);     /* Internal RCU use. */
bool rcu_gp_is_expedited(void);  /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
#endif /* #else #ifdef CONFIG_TINY_RCU */

enum rcutorture_type {
	RCU_FLAVOR,
	RCU_BH_FLAVOR,
	RCU_SCHED_FLAVOR,
	RCU_TASKS_FLAVOR,
	SRCU_FLAVOR,
	INVALID_RCU_FLAVOR
};

#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
			    unsigned long *gpnum, unsigned long *completed);
void rcutorture_record_test_transition(void);
void rcutorture_record_progress(unsigned long vernum);
void do_trace_rcu_torture_read(const char *rcutorturename,
			       struct rcu_head *rhp,
			       unsigned long secs,
			       unsigned long c_old,
			       unsigned long c);
#else
static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
					  int *flags,
					  unsigned long *gpnum,
					  unsigned long *completed)
{
	*flags = 0;
	*gpnum = 0;
	*completed = 0;
}
static inline void rcutorture_record_test_transition(void)
{
}
static inline void rcutorture_record_progress(unsigned long vernum)
{
}
#ifdef CONFIG_RCU_TRACE
void do_trace_rcu_torture_read(const char *rcutorturename,
			       struct rcu_head *rhp,
			       unsigned long secs,
			       unsigned long c_old,
			       unsigned long c);
#else
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
	do { } while (0)
#endif
#endif

#define UINT_CMP_GE(a, b)	(UINT_MAX / 2 >= (a) - (b))
#define UINT_CMP_LT(a, b)	(UINT_MAX / 2 < (a) - (b))
#define ULONG_CMP_GE(a, b)	(ULONG_MAX / 2 >= (a) - (b))
#define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))
#define ulong2long(a)		(*(long *)(&(a)))

/* Exported common interfaces */

#ifdef CONFIG_PREEMPT_RCU

/**
 * call_rcu() - Queue an RCU callback for invocation after a grace period.
 * @head: structure to be used for queueing the RCU updates.
 * @func: actual callback function to be invoked after the grace period
 *
 * The callback function will be invoked some time after a full grace
 * period elapses, in other words after all pre-existing RCU read-side
 * critical sections have completed.  However, the callback function
 * might well execute concurrently with RCU read-side critical sections
 * that started after call_rcu() was invoked.  RCU read-side critical
 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
 * and may be nested.
 *
 * Note that all CPUs must agree that the grace period extended beyond
 * all pre-existing RCU read-side critical section.  On systems with more
 * than one CPU, this means that when "func()" is invoked, each CPU is
 * guaranteed to have executed a full memory barrier since the end of its
 * last RCU read-side critical section whose beginning preceded the call
 * to call_rcu().  It also means that each CPU executing an RCU read-side
 * critical section that continues beyond the start of "func()" must have
 * executed a memory barrier after the call_rcu() but before the beginning
 * of that RCU read-side critical section.  Note that these guarantees
 * include CPUs that are offline, idle, or executing in user mode, as
 * well as CPUs that are executing in the kernel.
 *
 * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
 * resulting RCU callback function "func()", then both CPU A and CPU B are
 * guaranteed to execute a full memory barrier during the time interval
 * between the call to call_rcu() and the invocation of "func()" -- even
 * if CPU A and CPU B are the same CPU (but again only if the system has
 * more than one CPU).
 */
void call_rcu(struct rcu_head *head,
	      rcu_callback_t func);

#else /* #ifdef CONFIG_PREEMPT_RCU */

/* In classic RCU, call_rcu() is just call_rcu_sched(). */
#define	call_rcu	call_rcu_sched

#endif /* #else #ifdef CONFIG_PREEMPT_RCU */

/**
 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
 * @head: structure to be used for queueing the RCU updates.
 *