path: root/drivers/gpu/nvgpu/boardobj/boardobjgrp.c

/*
 * 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
 *
 * 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>

#ifdef CONFIG_RCU_TORTURE_TEST
extern int rcutorture_runnable; /* for sysctl */
#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */

#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
extern void rcutorture_record_test_transition(void);
extern void rcutorture_record_progress(unsigned long vernum);
extern void do_trace_rcu_torture_read(char *rcutorturename,
				      struct rcu_head *rhp,
				      unsigned long secs,
				      unsigned long c_old,
				      unsigned long c);
#else
static inline void rcutorture_record_test_transition(void)
{
}
static inline void rcutorture_record_progress(unsigned long vernum)
{
}
#ifdef CONFIG_RCU_TRACE
extern void do_trace_rcu_torture_read(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).
 */
extern void call_rcu(struct rcu_head *head,
			      void (*func)(struct rcu_head *head));

#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.
 * @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 currently executing RCU
 * read-side critical sections have completed. call_rcu_bh() assumes
 * that the read-side critical sections end on completion of a softirq
 * handler. This means that read-side critical sections in process
 * context must not be interrupted by softirqs. This interface is to be
 * used when most of the read-side critical sections are in softirq context.
 * RCU read-side critical sections are delimited by :
 *  - rcu_read_lock() and  rcu_read_unlock(), if in interrupt context.
 *  OR
 *  - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context.
 *  These may be nested.
 *
 * See the description of call_rcu() for more detailed information on
 * memory ordering guarantees.
 */
extern void call_rcu_bh(struct rcu_head *head,
			void (*func)(struct rcu_head *head));

/**
 * call_rcu_sched() - Queue an RCU for invocation after sched 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 currently executing RCU
 * read-side critical sections have completed. call_rcu_sched() assumes
 * that the read-side critical sections end on enabling of preemption
 * or on voluntary preemption.
 * RCU read-side critical sections are delimited by :
 *  - rcu_read_lock_sched() and  rcu_read_unlock_sched(),
 *  OR
 *  anything that disables preemption.
 *  These may be nested.
 *
 * See the description of call_rcu() for more detailed information on
 * memory ordering guarantees.
 */
extern void call_rcu_sched(struct rcu_head *head,
			   void (*func)(struct rcu_head *rcu));

extern void synchronize_sched(void);

#ifdef CONFIG_PREEMPT_RCU

extern void __rcu_read_lock(void);
extern void __rcu_read_unlock(void);
extern void rcu_read_unlock_special(struct task_struct *t);
void synchronize_rcu(void);

/*
 * Defined as a macro as it is a very low level header included from
 * areas that don't even know about current.  This gives the rcu_read_lock()
 * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
 * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
 */
#define rcu_preempt_depth() (current->rcu_read_lock_nesting)

#else /* #ifdef CONFIG_PREEMPT_RCU */

static inline void __rcu_read_lock(void)
{
	preempt_disable();
}

static inline void __rcu_read_unlock(void)
{
	preempt_enable();
}

static inline void synchronize_rcu(void)
{
	synchronize_sched();
}

static inline int rcu_preempt_depth(void)
{
	return 0;
}

#endif /* #else #ifdef CONFIG_PREEMPT_RCU */

/* Internal to kernel */
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_check_callbacks(int cpu, int user);
struct notifier_block;
extern void rcu_idle_enter(void);
extern void rcu_idle_exit(void);
extern void rcu_irq_enter(void);
extern void rcu_irq_exit(void);

#ifdef CONFIG_RCU_USER_QS
extern void rcu_user_enter(void);
extern void rcu_user_exit(void);
extern void rcu_user_enter_after_irq(void);
extern void rcu_user_exit_after_irq(void);
#else
static inline void rcu_user_enter(void) { }
static inline void rcu_user_exit(void) { }
static inline void rcu_user_enter_after_irq(void) { }
static inline void rcu_user_exit_after_irq(void) { }
static inline void rcu_user_hooks_switch(struct task_struct *prev,
					 struct task_struct *next) { }
#endif /* CONFIG_RCU_USER_QS */

extern void exit_rcu(void);

/**
 * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers
 * @a: Code that RCU needs to pay attention to.
 *
 * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden
 * in the inner idle loop, that is, between the rcu_idle_enter() and
 * the rcu_idle_exit() -- RCU will happily ignore any such read-side
 * critical sections.  However, things like powertop need tracepoints
 * in the inner idle loop.
 *
 * This macro provides the way out:  RCU_NONIDLE(do_something_with_RCU())
 * will tell RCU that it needs to pay attending, invoke its argument
 * (in this example, a call to the do_something_with_RCU() function),
 * and then tell RCU to go back to ignoring this CPU.  It is permissible
 * to nest RCU_NONIDLE() wrappers, but the nesting level is currently
 * quite limited.  If deeper nesting is required, it will be necessary
 * to adjust DYNTICK_TASK_NESTING_VALUE accordingly.
 */
#define RCU_NONIDLE(a) \
	do { \
		rcu_irq_enter(); \
		do { a; } while (0); \
		rcu_irq_exit(); \
	} while (0)

/*
 * Infrastructure to implement the synchronize_() primitives in
 * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
 */

typedef void call_rcu_func_t(struct rcu_head *head,
			     void (*func)(struct rcu_head *head));
void wait_rcu_gp(call_rcu_func_t crf);

#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
#include <linux/rcutree.h>
#elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
#include <linux/rcutiny.h>
#else
#error "Unknown RCU implementation specified to kernel configuration"
#endif

/*
 * init_rcu_head_on_stack()/destroy_rcu_head_on_stack() are needed for dynamic
 * initialization and destruction of rcu_head on the stack. rcu_head structures
 * allocated dynamically in the heap or defined statically don't need any
 * initialization.
 */
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
extern void init_rcu_head_on_stack(struct rcu_head *head);
extern void destroy_rcu_head_on_stack(struct rcu_head *head);
#else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
static inline void init_rcu_head_on_stack(struct rcu_head *head)
{
}

static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
{
}
#endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */

#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP)
extern int rcu_is_cpu_idle(void);
#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */

#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU)
bool rcu_lockdep_current_cpu_online(void);
#else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */
static inline bool rcu_lockdep_current_cpu_online(void)
{
	return 1;
}
#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */

#ifdef CONFIG_DEBUG_LOCK_ALLOC

static inline void rcu_lock_acquire(struct lockdep_map *map)
{
	lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_);
}

static inline void rcu_lock_release(struct lockdep_map *map)
{
	lock_release(map, 1, _THIS_IP_);
}

extern struct lockdep_map rcu_lock_map;
extern struct lockdep_map rcu_bh_lock_map;
extern struct lockdep_map rcu_sched_lock_map;
extern int debug_lockdep_rcu_enabled(void);

/**
 * rcu_read_lock_held() - might we be in RCU read-side critical section?
 *
 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU
 * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
 * this assumes we are in an RCU read-side critical section unless it can
 * prove otherwise.  This is useful for debug checks in functions that
 * require that they be called within an RCU read-side critical section.
 *
 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
 * and while lockdep is disabled.
 *
 * Note that rcu_read_lock() and the matching rcu_read_unlock() must
 * occur in the same context, for example, it is illegal to invoke
 * rcu_read_unlock() in process context if the matching rcu_read_lock()
 * was invoked from within an irq handler.
 *
 * Note that rcu_read_lock() is disallowed if the CPU is either idle or
 * offline from an RCU perspective, so check for those as well.
 */
static inline int rcu_read_lock_held(void)
{
	if (!debug_lockdep_rcu_enabled())
		return 1;
	if (rcu_is_cpu_idle())
		return 0;
	if (!rcu_lockdep_current_cpu_online())
		return 0;
	return lock_is_held(&rcu_lock_map);
}

/*
 * rcu_read_lock_bh_held() is defined out of line to avoid #include-file
 * hell.
 */
extern int rcu_read_lock_bh_held(void);

/**
 * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
 *
 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an
 * RCU-sched read-side critical section.  In absence of
 * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
 * critical section unless it can prove otherwise.  Note that disabling
 * of preemption (including disabling irqs) counts as an RCU-sched
 * read-side critical section.  This is useful for debug checks in functions
 * that required that they be called within an RCU-sched read-side
 * critical section.
 *
 * Check 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 rcu_read_lock_held() returns false even if the CPU
 * did an rcu_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.
 *
 * Similarly, we avoid claiming an SRCU read lock held if the current
 * CPU is offline.
 */
#ifdef CONFIG_PREEMPT_COUNT
static inline int rcu_read_lock_sched_held(void)
{
	int lockdep_opinion = 0;

	if (!debug_lockdep_rcu_enabled())
		return 1;
	if (rcu_is_cpu_idle())
		return 0;
	if (!rcu_lockdep_current_cpu_online())
		return 0;
	if (debug_locks)
		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
}
#else /* #ifdef CONFIG_PREEMPT_COUNT */
static inline int rcu_read_lock_sched_held(void)
{
	return 1;
}
#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */

#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

# define rcu_lock_acquire(a)		do { } while (0)
# define rcu_lock_release(a)		do { } while (0)

static inline int rcu_read_lock_held(void)
{
	return 1;
}

static inline int rcu_read_lock_bh_held(void)
{
	return 1;
}

#ifdef CONFIG_PREEMPT_COUNT
static inline int rcu_read_lock_sched_held(void)
{
	return preempt_count() != 0 || irqs_disabled();
}
#else /* #ifdef CONFIG_PREEMPT_COUNT */
static inline int rcu_read_lock_sched_held(void)
{
	return 1;
}
#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */

#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */

#ifdef CONFIG_PROVE_RCU

extern int rcu_my_thread_group_empty(void);

/**
 * rcu_lockdep_assert - emit lockdep splat if specified condition not met
 * @c: condition to check
 * @s: informative message
 */
#define rcu_lockdep_assert(c, s)					\
	do {								\
		static bool __section(.data.unlikely) __warned;		\
		if (debug_lockdep_rcu_enabled() && !__warned && !(c)) {	\
			__warned = true;				\
			lockdep_rcu_suspicious(__FILE__, __LINE__, s);	\
		}							\
	} while (0)

#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU)
static inline void rcu_preempt_sleep_check(void)
{
	rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
			   "Illegal context switch in RCU read-side critical section");
}
#else /* #ifdef CONFIG_PROVE_RCU */
static inline void rcu_preempt_sleep_check(void)
{
}
#endif /* #else #ifdef CONFIG_PROVE_RCU */

#define rcu_sleep_check()						\
	do {								\
		rcu_preempt_sleep_check();				\
		rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),	\
				   "Illegal context switch in RCU-bh"	\
				   " read-side critical section");	\
		rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),	\
				   "Illegal context switch in RCU-sched"\
				   " read-side critical section");	\
	} while (0)

#else /* #ifdef CONFIG_PROVE_RCU */

#define rcu_lockdep_assert(c, s) do { } while (0)
#define rcu_sleep_check() do { } while (0)

#endif /* #else #ifdef CONFIG_PROVE_RCU */

/*
 * Helper functions for rcu_dereference_check(), rcu_dereference_protected()
 * and rcu_assign_pointer().  Some of these could be folded into their
 * callers, but they are left separate in order to ease introduction of
 * multiple flavors of pointers to match the multiple flavors of RCU
 * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in
 * the future.
 */

#ifdef __CHECKER__
#define rcu_dereference_sparse(p, space) \
	((void)(((typeof(*p) space *)p) == p))
#else /* #ifdef __CHECKER__ */
#define rcu_dereference_sparse(p, space)
#endif /* #else #ifdef __CHECKER__ */

#define __rcu_access_pointer(p, space) \
	({ \
		typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
		rcu_dereference_sparse(p, space); \
		((typeof(*p) __force __kernel *)(_________p1)); \
	})
#define __rcu_dereference_check(p, c, space) \
	({ \
		typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
		rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \
				      " usage"); \
		rcu_dereference_sparse(p, space); \
		smp_read_barrier_depends(); \
		((typeof(*p) __force __kernel *)(_________p1)); \
	})
#define __rcu_dereference_protected(p, c, space) \
	({ \
		rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \
				      " usage"); \
		rcu_dereference_sparse(p, space); \
		((typeof(*p) __force __kernel *)(p)); \
	})

#define __rcu_access_index(p, space) \
	({ \
		typeof(p) _________p1 = ACCESS_ONCE(p); \
		rcu_dereference_sparse(p, space); \
		(_________p1); \
	})
#define __rcu_dereference_index_check(p, c) \
	({ \
		typeof(p) _________p1 = ACCESS_ONCE(p); \
		rcu_lockdep_assert(c, \
				   "suspicious rcu_dereference_index_check()" \
				   " usage"); \
		smp_read_barrier_depends(); \
		(_________p1); \
	})
#define __rcu_assign_pointer(p, v, space) \
	do { \
		smp_wmb(); \
		(p) = (typeof(*v) __force space *)(v); \
	} while (0)


/**
 * rcu_access_pointer() - fetch RCU pointer with no dereferencing
 * @p: The pointer to read
 *
 * Return the value of the specified RCU-protected pointer, but omit the
 * smp_read_barrier_depends() and keep the ACCESS_ONCE().  This is useful
 * when the value of this pointer is accessed, but the pointer is not
 * dereferenced, for example, when testing an RCU-protected pointer against
 * NULL.  Although rcu_access_pointer() may also be used in cases where
 * update-side locks prevent the value of the pointer from changing, you
 * should instead use rcu_dereference_protected() for this use case.
 *
 * It is also permissible to use rcu_access_pointer() when read-side
 * access to the pointer was removed at least one grace period ago, as
 * is the case in the context of the RCU callback that is freeing up
 * the data, or after a synchronize_rcu() returns.  This can be useful
 * when tearing down multi-linked structures after a grace period
 * has elapsed.
 */
#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu)

/**
 * rcu_dereference_check() - rcu_dereference with debug checking
 * @p: The pointer to read, prior to dereferencing
 * @c: The conditions under which the dereference will take place
 *
 * Do an rcu_dereference(), but check that the conditions under which the
 * dereference will take place are correct.  Typically the conditions
 * indicate the various locking conditions that should be held at that
 * point.  The check should return true if the conditions are satisfied.
 * An implicit check for being in an RCU read-side critical section
 * (rcu_read_lock()) is included.
 *
 * For example:
 *
 *	bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock));
 *
 * could be used to indicate to lockdep that foo->bar may only be dereferenced
 * if either rcu_read_lock() is held, or that the lock required to replace
 * the bar struct at foo->bar is held.
 *
 * Note that the list of conditions may also include indications of when a lock
 * need not be held, for example during initialisation or destruction of the
 * target struct:
 *
 *	bar = rcu_dereference_check(foo->bar, lockdep_is_held(&foo->lock) ||
 *					      atomic_read(&foo->usage) == 0);
 *
 * Inserts memory barriers on architectures that require them
 * (currently only the Alpha), prevents the compiler from refetching
 * (and from merging fetches), and, more importantly, documents exactly
 * which pointers are protected by RCU and checks that the pointer is
 * annotated as __rcu.
 */
#define rcu_dereference_check(p, c) \
	__rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu)

/**
 * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking
 * @p: The pointer to read, prior to dereferencing
 * @c: The conditions under which the dereference will take place
 *
 * This is the RCU-bh counterpart to rcu_dereference_check().
 */
#define rcu_dereference_bh_check(p, c) \
	__rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu)

/**
 * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking
 * @p: The pointer to read, prior to dereferencing
 * @c: The conditions under which the dereference will take place
 *
 * This is the RCU-sched counterpart to rcu_dereference_check().
 */
#define rcu_dereference_sched_check(p, c) \
	__rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \
				__rcu)

#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/

/*
 * The tracing infrastructure traces RCU (we want that), but unfortunately
 * some of the RCU checks causes tracing to lock up the system.
 *
 * The tracing version of rcu_dereference_raw() must not call
 * rcu_read_lock_held().
 */
#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)