Date:	Thu, 7 Apr 2011 22:13:59 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Lai Jiangshan <laijs@...fujitsu.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: Re: [RFC PATCH 4/5] RCU: Add TASK_RCU_OFFSET

On Fri, Apr 08, 2011 at 09:26:16AM +0800, Lai Jiangshan wrote:
> On 04/08/2011 12:26 AM, Paul E. McKenney wrote:
> > On Thu, Apr 07, 2011 at 08:47:37AM -0700, Paul E. McKenney wrote:
> >> On Thu, Apr 07, 2011 at 01:49:51PM +0800, Lai Jiangshan wrote:
> >>> On 04/07/2011 08:30 AM, Paul E. McKenney wrote:
> >>>> On Wed, Apr 06, 2011 at 02:27:39PM -0700, H. Peter Anvin wrote:
> >>>>> On 04/06/2011 02:06 PM, Peter Zijlstra wrote:
> >>>>>> On Wed, 2011-04-06 at 13:13 -0700, Paul E. McKenney wrote:
> >>>>>>> And the following patch builds correctly for defconfig x86 builds,
> >>>>>>> while allowing rcupdate.h to see the sched.h definitions as needed
> >>>>>>> to inline rcu_read_lock() and rcu_read_unlock().
> >>>>>>>
> >>>>>> Looks like an entirely reasonable patch to me ;-)
> >>>>>>
> >>>>>
> >>>>> Quite... a lot better than the original proposal!
> >>>>
> >>>> Glad you both like it!
> >>>>
> >>>> When I do an allyesconfig build, I do get errors during the "CHECK"
> >>>> phase, when it is putting things into the usr/include in the build tree.
> >>>> I believe that this is because I am exposing different header files to
> >>>> the library-export scripts.  The following patch silences some of them,
> >>>> but I am really out of my depth here.
> >>>>
> >>>> Sam, Jan, Michal, help?
> >>>>
> >>>> 							Thanx, Paul
> >>>>
> >>>> ------------------------------------------------------------------------
> >>>>
> >>>
> >>> Easy to split rcupdate.h, hard to resolve the dependence problem.
> >>>
> >>> You can apply the next additional patch when you test:
> >>
> >> I am sure that you are quite correct.  ;-)
> >>
> >> I am moving _rcu_read_lock() and _rcu_read_unlock() into
> >> include/linux/rcutree.h and include/linux/rcutiny.h, and I am sure that
> >> more pain will ensue.
> >>
> >> One thing I don't understand...  How does is it helping to group the
> >> task_struct RCU-related fields into a structure?  Is that generating
> >> better code on your platform due to smaller offsets or something?
> 
> You don't like task_rcu_struct patch? I think it can make code clearer,
> and it can also check the code even when CONFIG_PREEMPT_RCU=n.
> 
> For rcu_read_[un]lock(), it generates the same code, no better, no worse.
> 
> It is just a cleanup patch, it is helpless for making rcu_read_[un]lock() inline,
> if you don't like it, I will give up it.

I don't know that I feel strongly either way about it.  It was necessary
with the integer-offset approach, but optional now.

> >> Also, does your patchset address the CHECK warnings?
> > 
> > I take it back...  I applied the following patch on top of my earlier
> > one, and a defconfig x86 build completed without error.  (Though I have
> > not tested the results of the build.)
> > 
> > One possible difference -- I did this work on top of a recent Linus
> > git commit (b2a8b4b81966) rather than on top of my -rcu tree.  Also,
> > I have not yet tried an allyesconfig build, which will no doubt locate
> > some more problems.
> > 
> > 							Thanx, Paul
> > 
> 
> when defconfig or allyesconfig, CONFIG_PREEMPT=n and CONFIG_TREE_PREEMPT_RCU=n
> when you make them "y":
> 
> In file included from include/linux/rcupdate.h:764:0,
>                  from include/linux/tracepoint.h:19,
>                  from include/linux/module.h:18,
>                  from include/linux/crypto.h:21,
>                  from arch/x86/kernel/asm-offsets.c:8:
> include/linux/rcutree.h:50:20: error: static declaration of ‘__rcu_read_lock’ follows non-static declaration
> include/linux/rcupdate.h:76:13: note: previous declaration of ‘__rcu_read_lock’ was here
> include/linux/rcutree.h:63:20: error: static declaration of ‘__rcu_read_unlock’ follows non-static declaration
> include/linux/rcupdate.h:77:13: note: previous declaration of ‘__rcu_read_unlock’ was here
> make[1]: *** [arch/x86/kernel/asm-offsets.s] Error 1
> make: *** [prepare0] Error 2

Yep.  I need to move the rcu_read_lock() APIs to follow the inclusion
of rcutree.h and rcutiny.h.  Also add include of sched.h to rcutiny.h.
The code movement does bloat the patch a bit.  But rcu_assign_pointer()
must precede the inclusion of rcutree.h and rcutiny.h, so it is not
possible to simply move the inclusions.  See below.

							Thanx, Paul

------------------------------------------------------------------------

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 00cec4d..a243c13 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -648,6 +648,8 @@ struct sysinfo {
 #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
 #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
 
+#ifdef __KERNEL__
+
 /**
  * BUILD_BUG_ON - break compile if a condition is true.
  * @condition: the condition which the compiler should know is false.
@@ -673,6 +675,7 @@ extern int __build_bug_on_failed;
 		if (condition) __build_bug_on_failed = 1;	\
 	} while(0)
 #endif
+#endif /* __KERNEL__ */
 
 /* Trap pasters of __FUNCTION__ at compile-time */
 #define __FUNCTION__ (__func__)
diff --git a/include/linux/pid.h b/include/linux/pid.h
index efceda0..3c5719b 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -1,7 +1,7 @@
 #ifndef _LINUX_PID_H
 #define _LINUX_PID_H
 
-#include <linux/rcupdate.h>
+#include <linux/types.h>
 
 enum pid_type
 {
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ff422d2..55e941f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -33,6 +33,7 @@
 #ifndef __LINUX_RCUPDATE_H
 #define __LINUX_RCUPDATE_H
 
+#include <linux/types.h>
 #include <linux/cache.h>
 #include <linux/spinlock.h>
 #include <linux/threads.h>
@@ -52,16 +53,6 @@ extern int rcutorture_runnable; /* for sysctl */
 #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));
@@ -82,8 +73,6 @@ static inline void __rcu_read_unlock_bh(void)
 
 #ifdef CONFIG_PREEMPT_RCU
 
-extern void __rcu_read_lock(void);
-extern void __rcu_read_unlock(void);
 void synchronize_rcu(void);
 
 /*
@@ -141,14 +130,6 @@ 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
@@ -535,6 +516,134 @@ extern int rcu_my_thread_group_empty(void);
 #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));
+
+#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)
+{
+	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 */
+
+#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
+
+/**
  * rcu_read_lock() - mark the beginning of an RCU read-side critical section
  *
  * When synchronize_rcu() is invoked on one CPU while other CPUs
@@ -677,124 +786,4 @@ 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)
-{
-	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 */
-
 #endif /* __LINUX_RCUPDATE_H */
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 30ebd7c..167fb19 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -26,6 +26,7 @@
 #define __LINUX_TINY_H
 
 #include <linux/cache.h>
+#include <linux/sched.h>
 
 static inline void rcu_init(void)
 {
@@ -47,6 +48,40 @@ static inline void rcu_barrier(void)
 
 void rcu_barrier(void);
 void synchronize_rcu_expedited(void);
+void rcu_read_unlock_special(struct task_struct *t);
+
+/*
+ * Tiny-preemptible RCU implementation for rcu_read_lock().
+ * Just increment ->rcu_read_lock_nesting, shared state will be updated
+ * if we block.
+ */
+static inline void __rcu_read_lock(void)
+{
+	current->rcu_read_lock_nesting++;
+	barrier();
+}
+
+/*
+ * Tiny-preemptible RCU implementation for rcu_read_unlock().
+ * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
+ * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
+ * invoke rcu_read_unlock_special() to clean up after a context switch
+ * in an RCU read-side critical section and other special cases.
+ */
+static inline void __rcu_read_unlock(void)
+{
+	struct task_struct *t = current;
+
+	barrier();
+	--t->rcu_read_lock_nesting;
+	barrier();  /* decrement before load of ->rcu_read_unlock_special */
+	if (t->rcu_read_lock_nesting == 0 &&
+	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
+		rcu_read_unlock_special(t);
+#ifdef CONFIG_PROVE_LOCKING
+	WARN_ON_ONCE(t->rcu_read_lock_nesting < 0);
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
+}
 
 #endif /* #else #ifdef CONFIG_TINY_RCU */
 
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 3a93348..00a2b88 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -30,6 +30,8 @@
 #ifndef __LINUX_RCUTREE_H
 #define __LINUX_RCUTREE_H
 
+#include <linux/sched.h>
+
 extern void rcu_init(void);
 extern void rcu_note_context_switch(int cpu);
 extern int rcu_needs_cpu(int cpu);
@@ -38,6 +40,40 @@ extern void rcu_cpu_stall_reset(void);
 #ifdef CONFIG_TREE_PREEMPT_RCU
 
 extern void exit_rcu(void);
+extern void rcu_read_unlock_special(struct task_struct *t);
+
+/*
+ * Tree-preemptable RCU implementation for rcu_read_lock().
+ * Just increment ->rcu_read_lock_nesting, shared state will be updated
+ * if we block.
+ */
+static inline void __rcu_read_lock(void)
+{
+	current->rcu_read_lock_nesting++;
+	barrier();
+}
+
+/*
+ * Tree-preemptable RCU implementation for rcu_read_unlock().
+ * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
+ * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
+ * invoke rcu_read_unlock_special() to clean up after a context switch
+ * in an RCU read-side critical section and other special cases.
+ */
+static inline void __rcu_read_unlock(void)
+{
+	struct task_struct *t = current;
+
+	barrier();
+	--t->rcu_read_lock_nesting;
+	barrier();  /* decrement before load of ->rcu_read_unlock_special */
+	if (t->rcu_read_lock_nesting == 0 &&
+	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
+		rcu_read_unlock_special(t);
+#ifdef CONFIG_PROVE_LOCKING
+	WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0);
+#endif /* #ifdef CONFIG_PROVE_LOCKING */
+}
 
 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 83bd2e2..30a4444 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -78,7 +78,7 @@ struct sched_param {
 #include <linux/topology.h>
 #include <linux/proportions.h>
 #include <linux/seccomp.h>
-#include <linux/rcupdate.h>
+#include <linux/types.h>
 #include <linux/rculist.h>
 #include <linux/rtmutex.h>
 
@@ -2241,11 +2241,9 @@ int same_thread_group(struct task_struct *p1, struct task_struct *p2)
 	return p1->tgid == p2->tgid;
 }
 
-static inline struct task_struct *next_thread(const struct task_struct *p)
-{
-	return list_entry_rcu(p->thread_group.next,
-			      struct task_struct, thread_group);
-}
+/* Avoid #include hell for inlining rcu_read_lock(). */
+#define next_thread(p) \
+	list_entry_rcu((p)->thread_group.next, struct task_struct, thread_group)
 
 static inline int thread_group_empty(struct task_struct *p)
 {
diff --git a/include/linux/sem.h b/include/linux/sem.h
index f2961af..8489a1f 100644
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -78,7 +78,7 @@ struct  seminfo {
 
 #ifdef __KERNEL__
 #include <asm/atomic.h>
-#include <linux/rcupdate.h>
+#include <linux/types.h>
 #include <linux/cache.h>
 
 struct task_struct;
diff --git a/include/linux/soundcard.h b/include/linux/soundcard.h
index 1904afe..f99c32f 100644
--- a/include/linux/soundcard.h
+++ b/include/linux/soundcard.h
@@ -1064,7 +1064,9 @@ typedef struct mixer_vol_table {
  */
 #define SEQ_DECLAREBUF()		SEQ_USE_EXTBUF()
 
+#ifdef __KERNEL__
 void seqbuf_dump(void);	/* This function must be provided by programs */
+#endif
 
 #define SEQ_PM_DEFINES int __foo_bar___
 
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 11684d9..92fb6fa 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -19,6 +19,10 @@
  ****************************************************************
  */
 
+#ifdef __KERNEL__
+#include <linux/key.h>
+#endif
+
 #ifndef _LINUX_SYSCTL_H
 #define _LINUX_SYSCTL_H
 
@@ -1012,8 +1016,7 @@ extern int proc_do_large_bitmap(struct ctl_table *, int,
  */
 
 /* A sysctl table is an array of struct ctl_table: */
-struct ctl_table 
-{
+struct ctl_table {
 	const char *procname;		/* Text ID for /proc/sys, or zero */
 	void *data;
 	int maxlen;
diff --git a/include/linux/types.h b/include/linux/types.h
index 176da8c..868ef8b 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -231,6 +231,16 @@ struct hlist_node {
 	struct hlist_node *next, **pprev;
 };
 
+/**
+ * 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);
+};
+
 struct ustat {
 	__kernel_daddr_t	f_tfree;
 	__kernel_ino_t		f_tinode;
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index e9c9adc..bfa75df 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -8,6 +8,8 @@
  *
  */
 
+#include <linux/types.h>
+#include <asm/atomic.h>
 #include <linux/pid.h>
 #include <linux/pid_namespace.h>
 #include <linux/syscalls.h>
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 3cb8e36..d0e1ac3 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -520,23 +520,11 @@ void rcu_preempt_note_context_switch(void)
 }
 
 /*
- * Tiny-preemptible RCU implementation for rcu_read_lock().
- * Just increment ->rcu_read_lock_nesting, shared state will be updated
- * if we block.
- */
-void __rcu_read_lock(void)
-{
-	current->rcu_read_lock_nesting++;
-	barrier();  /* needed if we ever invoke rcu_read_lock in rcutiny.c */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_lock);
-
-/*
  * Handle special cases during rcu_read_unlock(), such as needing to
  * notify RCU core processing or task having blocked during the RCU
  * read-side critical section.
  */
-static void rcu_read_unlock_special(struct task_struct *t)
+void rcu_read_unlock_special(struct task_struct *t)
 {
 	int empty;
 	int empty_exp;
@@ -616,29 +604,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
 #endif /* #ifdef CONFIG_RCU_BOOST */
 	local_irq_restore(flags);
 }
-
-/*
- * Tiny-preemptible RCU implementation for rcu_read_unlock().
- * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
- * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
- * invoke rcu_read_unlock_special() to clean up after a context switch
- * in an RCU read-side critical section and other special cases.
- */
-void __rcu_read_unlock(void)
-{
-	struct task_struct *t = current;
-
-	barrier();  /* needed if we ever invoke rcu_read_unlock in rcutiny.c */
-	--t->rcu_read_lock_nesting;
-	barrier();  /* decrement before load of ->rcu_read_unlock_special */
-	if (t->rcu_read_lock_nesting == 0 &&
-	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
-		rcu_read_unlock_special(t);
-#ifdef CONFIG_PROVE_LOCKING
-	WARN_ON_ONCE(t->rcu_read_lock_nesting < 0);
-#endif /* #ifdef CONFIG_PROVE_LOCKING */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+EXPORT_SYMBOL_GPL(rcu_read_unlock_special);
 
 /*
  * Check for a quiescent state from the current CPU.  When a task blocks,
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index a363871..4b27afd 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -196,18 +196,6 @@ static void rcu_preempt_note_context_switch(int cpu)
 }
 
 /*
- * Tree-preemptable RCU implementation for rcu_read_lock().
- * Just increment ->rcu_read_lock_nesting, shared state will be updated
- * if we block.
- */
-void __rcu_read_lock(void)
-{
-	current->rcu_read_lock_nesting++;
-	barrier();  /* needed if we ever invoke rcu_read_lock in rcutree.c */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_lock);
-
-/*
  * Check for preempted RCU readers blocking the current grace period
  * for the specified rcu_node structure.  If the caller needs a reliable
  * answer, it must hold the rcu_node's ->lock.
@@ -261,7 +249,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
  * notify RCU core processing or task having blocked during the RCU
  * read-side critical section.
  */
-static void rcu_read_unlock_special(struct task_struct *t)
+void rcu_read_unlock_special(struct task_struct *t)
 {
 	int empty;
 	int empty_exp;
@@ -332,29 +320,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
 		local_irq_restore(flags);
 	}
 }
-
-/*
- * Tree-preemptable RCU implementation for rcu_read_unlock().
- * Decrement ->rcu_read_lock_nesting.  If the result is zero (outermost
- * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then
- * invoke rcu_read_unlock_special() to clean up after a context switch
- * in an RCU read-side critical section and other special cases.
- */
-void __rcu_read_unlock(void)
-{
-	struct task_struct *t = current;
-
-	barrier();  /* needed if we ever invoke rcu_read_unlock in rcutree.c */
-	--t->rcu_read_lock_nesting;
-	barrier();  /* decrement before load of ->rcu_read_unlock_special */
-	if (t->rcu_read_lock_nesting == 0 &&
-	    unlikely(ACCESS_ONCE(t->rcu_read_unlock_special)))
-		rcu_read_unlock_special(t);
-#ifdef CONFIG_PROVE_LOCKING
-	WARN_ON_ONCE(ACCESS_ONCE(t->rcu_read_lock_nesting) < 0);
-#endif /* #ifdef CONFIG_PROVE_LOCKING */
-}
-EXPORT_SYMBOL_GPL(__rcu_read_unlock);
+EXPORT_SYMBOL_GPL(rcu_read_unlock_special);
 
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
 
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