Message-ID: <4D9D622E.1080202@cn.fujitsu.com>
Date:	Thu, 07 Apr 2011 15:05:18 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Michal Marek <mmarek@...e.cz>,
	Jan Beulich <JBeulich@...ell.com>, Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	David Howells <dhowells@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 1/4] rcu: split rcupdate.h


Split rcupdate.h and move basic defines to rcupdate_defs.h.
It allows rcupdate.h using struct task_struct.

Only rcu_read_lock*() (which require struct task_struct) are left
in rcupdate.h. Some other code(example, the declaration of synchronize_rcu())
can also be left in rcupdate.h actually, but it is not required and
it will make the works more complex. So I also move them.
The result rcupdate_defs.h is a little big, but it just contains the RCU
defines and declarations, it is OK. Maybe rcupdate_basic.h is a better name?

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
 include/linux/rcupdate.h      |  616 +--------------------------------------
 include/linux/rcupdate_defs.h |  653 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 654 insertions(+), 615 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index dd4cd6d..c25d2a6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -33,42 +33,7 @@
 #ifndef __LINUX_RCUPDATE_H
 #define __LINUX_RCUPDATE_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/compiler.h>
-
-#ifdef CONFIG_RCU_TORTURE_TEST
-extern int rcutorture_runnable; /* for sysctl */
-#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
-
-#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))
-
-/**
- * struct rcu_head - callback structure for use with RCU
- * @next: next update requests in a list
- * @func: actual update function to call after the grace period.
- */
-struct rcu_head {
-	struct rcu_head *next;
-	void (*func)(struct rcu_head *head);
-};
-
-/* Exported common interfaces */
-extern void call_rcu_sched(struct rcu_head *head,
-			   void (*func)(struct rcu_head *rcu));
-extern void synchronize_sched(void);
-extern void rcu_barrier_bh(void);
-extern void rcu_barrier_sched(void);
-extern int sched_expedited_torture_stats(char *page);
+#include <linux/rcupdate_defs.h>
 
 static inline void __rcu_read_lock_bh(void)
 {
@@ -84,7 +49,6 @@ static inline void __rcu_read_unlock_bh(void)
 
 extern void __rcu_read_lock(void);
 extern void __rcu_read_unlock(void);
-void synchronize_rcu(void);
 
 /*
  * Defined as a macro as it is a very low level header included from
@@ -106,11 +70,6 @@ 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;
@@ -118,402 +77,6 @@ static inline int rcu_preempt_depth(void)
 
 #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;
-
-#ifdef CONFIG_NO_HZ
-
-extern void rcu_enter_nohz(void);
-extern void rcu_exit_nohz(void);
-
-#else /* #ifdef CONFIG_NO_HZ */
-
-static inline void rcu_enter_nohz(void)
-{
-}
-
-static inline void rcu_exit_nohz(void)
-{
-}
-
-#endif /* #else #ifdef CONFIG_NO_HZ */
-
-#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 */
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-
-extern struct lockdep_map rcu_lock_map;
-# define rcu_read_acquire() \
-		lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release()	lock_release(&rcu_lock_map, 1, _THIS_IP_)
-
-extern struct lockdep_map rcu_bh_lock_map;
-# define rcu_read_acquire_bh() \
-		lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release_bh()	lock_release(&rcu_bh_lock_map, 1, _THIS_IP_)
-
-extern struct lockdep_map rcu_sched_lock_map;
-# define rcu_read_acquire_sched() \
-		lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
-# define rcu_read_release_sched() \
-		lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
-
-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.
- */
-static inline int rcu_read_lock_held(void)
-{
-	if (!debug_lockdep_rcu_enabled())
-		return 1;
-	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.
- */
-#ifdef CONFIG_PREEMPT
-static inline int rcu_read_lock_sched_held(void)
-{
-	int lockdep_opinion = 0;
-
-	if (!debug_lockdep_rcu_enabled())
-		return 1;
-	if (debug_locks)
-		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
-	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
-}
-#else /* #ifdef CONFIG_PREEMPT */
-static inline int rcu_read_lock_sched_held(void)
-{
-	return 1;
-}
-#endif /* #else #ifdef CONFIG_PREEMPT */
-
-#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-
-# define rcu_read_acquire()		do { } while (0)
-# define rcu_read_release()		do { } while (0)
-# define rcu_read_acquire_bh()		do { } while (0)
-# define rcu_read_release_bh()		do { } while (0)
-# define rcu_read_acquire_sched()	do { } while (0)
-# define rcu_read_release_sched()	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
-static inline int rcu_read_lock_sched_held(void)
-{
-	return preempt_count() != 0 || irqs_disabled();
-}
-#else /* #ifdef CONFIG_PREEMPT */
-static inline int rcu_read_lock_sched_held(void)
-{
-	return 1;
-}
-#endif /* #else #ifdef CONFIG_PREEMPT */
-
-#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
- */
-#define rcu_lockdep_assert(c)						\
-	do {								\
-		static bool __warned;					\
-		if (debug_lockdep_rcu_enabled() && !__warned && !(c)) {	\
-			__warned = true;				\
-			lockdep_rcu_dereference(__FILE__, __LINE__);	\
-		}							\
-	} while (0)
-
-#else /* #ifdef CONFIG_PROVE_RCU */
-
-#define rcu_lockdep_assert(c) 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); \
-		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); \
-		rcu_dereference_sparse(p, space); \
-		((typeof(*p) __force __kernel *)(p)); \
-	})
-
-#define __rcu_dereference_index_check(p, c) \
-	({ \
-		typeof(p) _________p1 = ACCESS_ONCE(p); \
-		rcu_lockdep_assert(c); \
-		smp_read_barrier_depends(); \
-		(_________p1); \
-	})
-#define __rcu_assign_pointer(p, v, space) \
-	({ \
-		if (!__builtin_constant_p(v) || \
-		    ((v) != NULL)) \
-			smp_wmb(); \
-		(p) = (typeof(*v) __force space *)(v); \
-	})
-
-
-/**
- * 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.
- */
-#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? @@@*/
-
-/**
- * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
- * @p: The pointer to read, prior to dereferencing
- * @c: The conditions under which the dereference will take place
- *
- * Similar to rcu_dereference_check(), but omits the sparse checking.
- * This allows rcu_dereference_index_check() to be used on integers,
- * which can then be used as array indices.  Attempting to use
- * rcu_dereference_check() on an integer will give compiler warnings
- * because the sparse address-space mechanism relies on dereferencing
- * the RCU-protected pointer.  Dereferencing integers is not something
- * that even gcc will put up with.
- *
- * Note that this function does not implicitly check for RCU read-side
- * critical sections.  If this function gains lots of uses, it might
- * make sense to provide versions for each flavor of RCU, but it does
- * not make sense as of early 2010.
- */
-#define rcu_dereference_index_check(p, c) \
-	__rcu_dereference_index_check((p), (c))
-
-/**
- * rcu_dereference_protected() - fetch RCU pointer when updates prevented
- * @p: The pointer to read, prior to dereferencing
- * @c: The conditions under which the dereference will take place
- *
- * Return the value of the specified RCU-protected pointer, but omit
- * both the smp_read_barrier_depends() and the ACCESS_ONCE().  This
- * is useful in cases where update-side locks prevent the value of the
- * pointer from changing.  Please note that this primitive does -not-
- * prevent the compiler from repeating this reference or combining it
- * with other references, so it should not be used without protection
- * of appropriate locks.
- *
- * This function is only for update-side use.  Using this function
- * when protected only by rcu_read_lock() will result in infrequent
- * but very ugly failures.
- */
-#define rcu_dereference_protected(p, c) \
-	__rcu_dereference_protected((p), (c), __rcu)
-
-/**
- * rcu_dereference_bh_protected() - fetch RCU-bh pointer when updates prevented
- * @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_protected().
- */
-#define rcu_dereference_bh_protected(p, c) \
-	__rcu_dereference_protected((p), (c), __rcu)
-
-/**
- * rcu_dereference_sched_protected() - fetch RCU-sched pointer when updates prevented
- * @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_protected().
- */
-#define rcu_dereference_sched_protected(p, c) \
-	__rcu_dereference_protected((p), (c), __rcu)
-
-
-/**
- * rcu_dereference() - fetch RCU-protected pointer for dereferencing
- * @p: The pointer to read, prior to dereferencing
- *
- * This is a simple wrapper around rcu_dereference_check().
- */
-#define rcu_dereference(p) rcu_dereference_check(p, 0)
-
-/**
- * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing
- * @p: The pointer to read, prior to dereferencing
- *
- * Makes rcu_dereference_check() do the dirty work.
- */
-#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0)
-
-/**
- * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing
- * @p: The pointer to read, prior to dereferencing
- *
- * Makes rcu_dereference_check() do the dirty work.
- */
-#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
-
 /**
  * rcu_read_lock() - mark the beginning of an RCU read-side critical section
  *
@@ -657,181 +220,4 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 	preempt_enable_notrace();
 }
 
-/**
- * rcu_assign_pointer() - assign to RCU-protected pointer
- * @p: pointer to assign to
- * @v: value to assign (publish)
- *
- * Assigns the specified value to the specified RCU-protected
- * pointer, ensuring that any concurrent RCU readers will see
- * any prior initialization.  Returns the value assigned.
- *
- * Inserts memory barriers on architectures that require them
- * (pretty much all of them other than x86), and also prevents
- * the compiler from reordering the code that initializes the
- * structure after the pointer assignment.  More importantly, this
- * call documents which pointers will be dereferenced by RCU read-side
- * code.
- */
-#define rcu_assign_pointer(p, v) \
-	__rcu_assign_pointer((p), (v), __rcu)
-
-/**
- * RCU_INIT_POINTER() - initialize an RCU protected pointer
- *
- * Initialize an RCU-protected pointer in such a way to avoid RCU-lockdep
- * splats.
- */
-#define RCU_INIT_POINTER(p, v) \
-		p = (typeof(*v) __force __rcu *)(v)
-
-/* Infrastructure to implement the synchronize_() primitives. */
-
-struct rcu_synchronize {
-	struct rcu_head head;
-	struct completion completion;
-};
-
-extern void wakeme_after_rcu(struct rcu_head  *head);
-
-#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.
- */
-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.
- */
-extern void call_rcu_bh(struct rcu_head *head,
-			void (*func)(struct rcu_head *head));
-
-/*
- * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
- * by call_rcu() and rcu callback execution, and are therefore not part of the
- * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
- */
-
-#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
-# define STATE_RCU_HEAD_READY	0
-# define STATE_RCU_HEAD_QUEUED	1
-
-extern struct debug_obj_descr rcuhead_debug_descr;
-
-static inline void debug_rcu_head_queue(struct rcu_head *head)
-{
-	WARN_ON_ONCE((unsigned long)head & 0x3);
-	debug_object_activate(head, &rcuhead_debug_descr);
-	debug_object_active_state(head, &rcuhead_debug_descr,
-				  STATE_RCU_HEAD_READY,
-				  STATE_RCU_HEAD_QUEUED);
-}
-
-static inline void debug_rcu_head_unqueue(struct rcu_head *head)
-{
-	debug_object_active_state(head, &rcuhead_debug_descr,
-				  STATE_RCU_HEAD_QUEUED,
-				  STATE_RCU_HEAD_READY);
-	debug_object_deactivate(head, &rcuhead_debug_descr);
-}
-#else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
-static inline void debug_rcu_head_queue(struct rcu_head *head)
-{
-}
-
-static inline void debug_rcu_head_unqueue(struct rcu_head *head)
-{
-}
-#endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
-
-static __always_inline bool __is_kfree_rcu_offset(unsigned long offset)
-{
-	return offset < 4096;
-}
-
-static __always_inline
-void __kfree_rcu(struct rcu_head *head, unsigned long offset)
-{
-	typedef void (*rcu_callback)(struct rcu_head *);
-
-	BUILD_BUG_ON(!__builtin_constant_p(offset));
-
-	/* See the kfree_rcu() header comment. */
-	BUILD_BUG_ON(!__is_kfree_rcu_offset(offset));
-
-	call_rcu(head, (rcu_callback)offset);
-}
-
-extern void kfree(const void *);
-
-static inline void __rcu_reclaim(struct rcu_head *head)
-{
-	unsigned long offset = (unsigned long)head->func;
-
-	if (__is_kfree_rcu_offset(offset))
-		kfree((void *)head - offset);
-	else
-		head->func(head);
-}
-
-/**
- * kfree_rcu() - kfree an object after a grace period.
- * @ptr:	pointer to kfree
- * @rcu_head:	the name of the struct rcu_head within the type of @ptr.
- *
- * Many rcu callbacks functions just call kfree() on the base structure.
- * These functions are trivial, but their size adds up, and furthermore
- * when they are used in a kernel module, that module must invoke the
- * high-latency rcu_barrier() function at module-unload time.
- *
- * The kfree_rcu() function handles this issue.  Rather than encoding a
- * function address in the embedded rcu_head structure, kfree_rcu() instead
- * encodes the offset of the rcu_head structure within the base structure.
- * Because the functions are not allowed in the low-order 4096 bytes of
- * kernel virtual memory, offsets up to 4095 bytes can be accommodated.
- * If the offset is larger than 4095 bytes, a compile-time error will
- * be generated in __kfree_rcu().  If this error is triggered, you can
- * either fall back to use of call_rcu() or rearrange the structure to
- * position the rcu_head structure into the first 4096 bytes.
- *
- * Note that the allowable offset might decrease in the future, for example,
- * to allow something like kmem_cache_free_rcu().
- */
-#define kfree_rcu(ptr, rcu_head)					\
-	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
-
 #endif /* __LINUX_RCUPDATE_H */
diff --git a/include/linux/rcupdate_defs.h b/include/linux/rcupdate_defs.h
new file mode 100644
index 0000000..ae84745
--- /dev/null
+++ b/include/linux/rcupdate_defs.h
@@ -0,0 +1,653 @@
+/*
+ * 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@...ibm.com>
+ *
+ * Based on the original work by Paul McKenney <paulmck@...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_DEFS_H
+#define __LINUX_RCUPDATE_DEFS_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/compiler.h>
+
+#ifdef CONFIG_RCU_TORTURE_TEST
+extern int rcutorture_runnable; /* for sysctl */
+#endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
+
+#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))
+
+/**
+ * struct rcu_head - callback structure for use with RCU
+ * @next: next update requests in a list
+ * @func: actual update function to call after the grace period.
+ */
+struct rcu_head {
+	struct rcu_head *next;
+	void (*func)(struct rcu_head *head);
+};
+
+/* Exported common interfaces */
+extern void call_rcu_sched(struct rcu_head *head,
+			   void (*func)(struct rcu_head *rcu));
+extern void synchronize_sched(void);
+extern void rcu_barrier_bh(void);
+extern void rcu_barrier_sched(void);
+extern int sched_expedited_torture_stats(char *page);
+
+/* 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;
+
+#ifdef CONFIG_NO_HZ
+
+extern void rcu_enter_nohz(void);
+extern void rcu_exit_nohz(void);
+
+#else /* #ifdef CONFIG_NO_HZ */
+
+static inline void rcu_enter_nohz(void)
+{
+}
+
+static inline void rcu_exit_nohz(void)
+{
+}
+
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+#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 */
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+extern struct lockdep_map rcu_lock_map;
+# define rcu_read_acquire() \
+		lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release()	lock_release(&rcu_lock_map, 1, _THIS_IP_)
+
+extern struct lockdep_map rcu_bh_lock_map;
+# define rcu_read_acquire_bh() \
+		lock_acquire(&rcu_bh_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release_bh()	lock_release(&rcu_bh_lock_map, 1, _THIS_IP_)
+
+extern struct lockdep_map rcu_sched_lock_map;
+# define rcu_read_acquire_sched() \
+		lock_acquire(&rcu_sched_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release_sched() \
+		lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
+
+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.
+ */
+static inline int rcu_read_lock_held(void)
+{
+	if (!debug_lockdep_rcu_enabled())
+		return 1;
+	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.
+ */
+#ifdef CONFIG_PREEMPT
+static inline int rcu_read_lock_sched_held(void)
+{
+	int lockdep_opinion = 0;
+
+	if (!debug_lockdep_rcu_enabled())
+		return 1;
+	if (debug_locks)
+		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
+	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
+}
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+	return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
+
+#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+# define rcu_read_acquire()		do { } while (0)
+# define rcu_read_release()		do { } while (0)
+# define rcu_read_acquire_bh()		do { } while (0)
+# define rcu_read_release_bh()		do { } while (0)
+# define rcu_read_acquire_sched()	do { } while (0)
+# define rcu_read_release_sched()	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
+static inline int rcu_read_lock_sched_held(void)
+{
+	return preempt_count() != 0 || irqs_disabled();
+}
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+	return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
+
+#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
+ */
+#define rcu_lockdep_assert(c)						\
+	do {								\
+		static bool __warned;					\
+		if (debug_lockdep_rcu_enabled() && !__warned && !(c)) {	\
+			__warned = true;				\
+			lockdep_rcu_dereference(__FILE__, __LINE__);	\
+		}							\
+	} while (0)
+
+#else /* #ifdef CONFIG_PROVE_RCU */
+
+#define rcu_lockdep_assert(c) 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); \
+		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); \
+		rcu_dereference_sparse(p, space); \
+		((typeof(*p) __force __kernel *)(p)); \
+	})
+
+#define __rcu_dereference_index_check(p, c) \
+	({ \
+		typeof(p) _________p1 = ACCESS_ONCE(p); \
+		rcu_lockdep_assert(c); \
+		smp_read_barrier_depends(); \
+		(_________p1); \
+	})
+#define __rcu_assign_pointer(p, v, space) \
+	({ \
+		if (!__builtin_constant_p(v) || \
+		    ((v) != NULL)) \
+			smp_wmb(); \
+		(p) = (typeof(*v) __force space *)(v); \
+	})
+
+
+/**
+ * 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.
+ */
+#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? @@@*/
+
+/**
+ * rcu_dereference_index_check() - rcu_dereference for indices with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Similar to rcu_dereference_check(), but omits the sparse checking.
+ * This allows rcu_dereference_index_check() to be used on integers,
+ * which can then be used as array indices.  Attempting to use
+ * rcu_dereference_check() on an integer will give compiler warnings
+ * because the sparse address-space mechanism relies on dereferencing
+ * the RCU-protected pointer.  Dereferencing integers is not something
+ * that even gcc will put up with.
+ *
+ * Note that this function does not implicitly check for RCU read-side
+ * critical sections.  If this function gains lots of uses, it might
+ * make sense to provide versions for each flavor of RCU, but it does
+ * not make sense as of early 2010.
+ */
+#define rcu_dereference_index_check(p, c) \
+	__rcu_dereference_index_check((p), (c))
+
+/**
+ * rcu_dereference_protected() - fetch RCU pointer when updates prevented
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * Return the value of the specified RCU-protected pointer, but omit
+ * both the smp_read_barrier_depends() and the ACCESS_ONCE().  This
+ * is useful in cases where update-side locks prevent the value of the
+ * pointer from changing.  Please note that this primitive does -not-
+ * prevent the compiler from repeating this reference or combining it
+ * with other references, so it should not be used without protection
+ * of appropriate locks.
+ *
+ * This function is only for update-side use.  Using this function
+ * when protected only by rcu_read_lock() will result in infrequent
+ * but very ugly failures.
+ */
+#define rcu_dereference_protected(p, c) \
+	__rcu_dereference_protected((p), (c), __rcu)
+
+/**
+ * rcu_dereference_bh_protected() - fetch RCU-bh pointer when updates prevented
+ * @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_protected().
+ */
+#define rcu_dereference_bh_protected(p, c) \
+	__rcu_dereference_protected((p), (c), __rcu)
+
+/**
+ * rcu_dereference_sched_protected() - fetch RCU-sched pointer when updates prevented
+ * @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_protected().
+ */
+#define rcu_dereference_sched_protected(p, c) \
+	__rcu_dereference_protected((p), (c), __rcu)
+
+
+/**
+ * rcu_dereference() - fetch RCU-protected pointer for dereferencing
+ * @p: The pointer to read, prior to dereferencing
+ *
+ * This is a simple wrapper around rcu_dereference_check().
+ */
+#define rcu_dereference(p) rcu_dereference_check(p, 0)
+
+/**
+ * rcu_dereference_bh() - fetch an RCU-bh-protected pointer for dereferencing
+ * @p: The pointer to read, prior to dereferencing
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_bh(p) rcu_dereference_bh_check(p, 0)
+
+/**
+ * rcu_dereference_sched() - fetch RCU-sched-protected pointer for dereferencing
+ * @p: The pointer to read, prior to dereferencing
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
+
+/**
+ * rcu_assign_pointer() - assign to RCU-protected pointer
+ * @p: pointer to assign to
+ * @v: value to assign (publish)
+ *
+ * Assigns the specified value to the specified RCU-protected
+ * pointer, ensuring that any concurrent RCU readers will see
+ * any prior initialization.  Returns the value assigned.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (pretty much all of them other than x86), and also prevents
+ * the compiler from reordering the code that initializes the
+ * structure after the pointer assignment.  More importantly, this
+ * call documents which pointers will be dereferenced by RCU read-side
+ * code.
+ */
+#define rcu_assign_pointer(p, v) \
+	__rcu_assign_pointer((p), (v), __rcu)
+
+/**
+ * RCU_INIT_POINTER() - initialize an RCU protected pointer
+ *
+ * Initialize an RCU-protected pointer in such a way to avoid RCU-lockdep
+ * splats.
+ */
+#define RCU_INIT_POINTER(p, v) \
+		p = (typeof(*v) __force __rcu *)(v)
+
+/* Infrastructure to implement the synchronize_() primitives. */
+
+struct rcu_synchronize {
+	struct rcu_head head;
+	struct completion completion;
+};
+
+extern void wakeme_after_rcu(struct rcu_head  *head);
+
+#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.
+ */
+extern void call_rcu(struct rcu_head *head,
+			      void (*func)(struct rcu_head *head));
+
+void synchronize_rcu(void);
+
+#else /* #ifdef CONFIG_PREEMPT_RCU */
+
+/* In classic RCU, call_rcu() is just call_rcu_sched(). */
+#define	call_rcu	call_rcu_sched
+
+static inline void synchronize_rcu(void)
+{
+	synchronize_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.
+ */
+extern void call_rcu_bh(struct rcu_head *head,
+			void (*func)(struct rcu_head *head));
+
+/*
+ * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
+ * by call_rcu() and rcu callback execution, and are therefore not part of the
+ * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
+ */
+
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+# define STATE_RCU_HEAD_READY	0
+# define STATE_RCU_HEAD_QUEUED	1
+
+extern struct debug_obj_descr rcuhead_debug_descr;
+
+static inline void debug_rcu_head_queue(struct rcu_head *head)
+{
+	WARN_ON_ONCE((unsigned long)head & 0x3);
+	debug_object_activate(head, &rcuhead_debug_descr);
+	debug_object_active_state(head, &rcuhead_debug_descr,
+				  STATE_RCU_HEAD_READY,
+				  STATE_RCU_HEAD_QUEUED);
+}
+
+static inline void debug_rcu_head_unqueue(struct rcu_head *head)
+{
+	debug_object_active_state(head, &rcuhead_debug_descr,
+				  STATE_RCU_HEAD_QUEUED,
+				  STATE_RCU_HEAD_READY);
+	debug_object_deactivate(head, &rcuhead_debug_descr);
+}
+#else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+static inline void debug_rcu_head_queue(struct rcu_head *head)
+{
+}
+
+static inline void debug_rcu_head_unqueue(struct rcu_head *head)
+{
+}
+#endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+
+static __always_inline bool __is_kfree_rcu_offset(unsigned long offset)
+{
+	return offset < 4096;
+}
+
+static __always_inline
+void __kfree_rcu(struct rcu_head *head, unsigned long offset)
+{
+	typedef void (*rcu_callback)(struct rcu_head *);
+
+	BUILD_BUG_ON(!__builtin_constant_p(offset));
+
+	/* See the kfree_rcu() header comment. */
+	BUILD_BUG_ON(!__is_kfree_rcu_offset(offset));
+
+	call_rcu(head, (rcu_callback)offset);
+}
+
+extern void kfree(const void *);
+
+static inline void __rcu_reclaim(struct rcu_head *head)
+{
+	unsigned long offset = (unsigned long)head->func;
+
+	if (__is_kfree_rcu_offset(offset))
+		kfree((void *)head - offset);
+	else
+		head->func(head);
+}
+
+/**
+ * kfree_rcu() - kfree an object after a grace period.
+ * @ptr:	pointer to kfree
+ * @rcu_head:	the name of the struct rcu_head within the type of @ptr.
+ *
+ * Many rcu callbacks functions just call kfree() on the base structure.
+ * These functions are trivial, but their size adds up, and furthermore
+ * when they are used in a kernel module, that module must invoke the
+ * high-latency rcu_barrier() function at module-unload time.
+ *
+ * The kfree_rcu() function handles this issue.  Rather than encoding a
+ * function address in the embedded rcu_head structure, kfree_rcu() instead
+ * encodes the offset of the rcu_head structure within the base structure.
+ * Because the functions are not allowed in the low-order 4096 bytes of
+ * kernel virtual memory, offsets up to 4095 bytes can be accommodated.
+ * If the offset is larger than 4095 bytes, a compile-time error will
+ * be generated in __kfree_rcu().  If this error is triggered, you can
+ * either fall back to use of call_rcu() or rearrange the structure to
+ * position the rcu_head structure into the first 4096 bytes.
+ *
+ * Note that the allowable offset might decrease in the future, for example,
+ * to allow something like kmem_cache_free_rcu().
+ */
+#define kfree_rcu(ptr, rcu_head)					\
+	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
+
+#endif /* __LINUX_RCUPDATE_DEFS_H */
-- 
1.7.4

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