synchronize_sched() without migration

diff -urpNa -X dontdiff linux-2.6.22.1-rt4/include/linux/rcuclassic.h linux-2.6.22.1-rt4-sched/include/linux/rcuclassic.h
@@ -43,78 +43,19 @@
 #include <linux/seqlock.h>
 
 
-/* Global control variables for rcupdate callback mechanism. */
-struct rcu_ctrlblk {
-	long	cur;		/* Current batch number.                      */
-	long	completed;	/* Number of the last completed batch         */
-	int	next_pending;	/* Is the next batch already waiting?         */
-
-	int	signaled;
-
-	spinlock_t	lock	____cacheline_internodealigned_in_smp;
-	cpumask_t	cpumask; /* CPUs that need to switch in order    */
-	                         /* for current batch to proceed.        */
-} ____cacheline_internodealigned_in_smp;
-
-/* Is batch a before batch b ? */
-static inline int rcu_batch_before(long a, long b)
-{
-        return (a - b) < 0;
-}
-
-/* Is batch a after batch b ? */
-static inline int rcu_batch_after(long a, long b)
-{
-        return (a - b) > 0;
-}
+DECLARE_PER_CPU(int, rcu_data_bh_passed_quiesc);
 
 /*
- * Per-CPU data for Read-Copy UPdate.
- * nxtlist - new callbacks are added here
- * curlist - current batch for which quiescent cycle started if any
- */
-struct rcu_data {
-	/* 1) quiescent state handling : */
-	long		quiescbatch;     /* Batch # for grace period */
-	int		passed_quiesc;	 /* User-mode/idle loop etc. */
-	int		qs_pending;	 /* core waits for quiesc state */
-
-	/* 2) batch handling */
-	long  	       	batch;           /* Batch # for current RCU batch */
-	struct rcu_head *nxtlist;
-	struct rcu_head **nxttail;
-	long            qlen; 	 	 /* # of queued callbacks */
-	struct rcu_head *curlist;
-	struct rcu_head **curtail;
-	struct rcu_head *donelist;
-	struct rcu_head **donetail;
-	long		blimit;		 /* Upper limit on a processed batch */
-	int cpu;
-};
-
-DECLARE_PER_CPU(struct rcu_data, rcu_data);
-DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
-
-/*
- * Increment the quiescent state counter.
+ * Increment the bottom-half quiescent state counter.
  * The counter is a bit degenerated: We do not need to know
  * how many quiescent states passed, just if there was at least
  * one since the start of the grace period. Thus just a flag.
  */
-static inline void rcu_qsctr_inc(int cpu)
-{
-	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-	rdp->passed_quiesc = 1;
-}
 static inline void rcu_bh_qsctr_inc(int cpu)
 {
-	struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-	rdp->passed_quiesc = 1;
+	per_cpu(rcu_data_bh_passed_quiesc, cpu) = 1;
 }
 
-extern int rcu_pending(int cpu);
-extern int rcu_needs_cpu(int cpu);
-
 #define __rcu_read_lock() \
 	do { \
 		preempt_disable(); \

@@ -139,13 +80,15 @@ extern int rcu_needs_cpu(int cpu);
 
 #define __synchronize_sched()	synchronize_rcu()
 
-extern void __rcu_init(void);
-extern void rcu_check_callbacks(int cpu, int user);
-extern void rcu_restart_cpu(int cpu);
-extern long rcu_batches_completed(void);
+#define rcu_advance_callbacks_rt(cpu, user)
+#define rcu_check_callbacks_rt(cpu, user)
+#define rcu_init_rt()
+#define rcu_needs_cpu_rt(cpu) 0
+#define rcu_pending_rt(cpu) 0
+#define rcu_process_callbacks_rt(unused)
 
-struct softirq_action;
-extern void rcu_process_callbacks(struct softirq_action *unused);
+extern void FASTCALL(call_rcu_classic(struct rcu_head *head,
+				      void (*func)(struct rcu_head *head)));
 
 #endif /* __KERNEL__ */
 #endif /* __LINUX_RCUCLASSIC_H */

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diff -urpNa -X dontdiff linux-2.6.22.1-rt4/include/linux/rcupreempt.h linux-2.6.22.1-rt4-sched/include/linux/rcupreempt.h
@@ -42,30 +42,27 @@
 #include <linux/cpumask.h>
 #include <linux/seqlock.h>
 
-#define rcu_qsctr_inc(cpu)
-#define rcu_bh_qsctr_inc(cpu)
 #define call_rcu_bh(head, rcu) call_rcu(head, rcu)
-
-extern void __rcu_read_lock(void);
-extern void __rcu_read_unlock(void);
-extern int rcu_pending(int cpu);
-extern int rcu_needs_cpu(int cpu);
-
+#define rcu_bh_qsctr_inc(cpu)
 #define __rcu_read_lock_bh()	{ rcu_read_lock(); local_bh_disable(); }
 #define __rcu_read_unlock_bh()	{ local_bh_enable(); rcu_read_unlock(); }
-
 #define __rcu_read_lock_nesting()	(current->rcu_read_lock_nesting)
 
+extern void FASTCALL(call_rcu_classic(struct rcu_head *head,
+				      void (*func)(struct rcu_head *head)));
+extern void FASTCALL(call_rcu_preempt(struct rcu_head *head,
+				      void (*func)(struct rcu_head *head)));
+extern void __rcu_read_lock(void);
+extern void __rcu_read_unlock(void);
 extern void __synchronize_sched(void);
 
-extern void __rcu_init(void);
-extern void rcu_check_callbacks(int cpu, int user);
-extern void rcu_restart_cpu(int cpu);
-extern long rcu_batches_completed(void);
-
+extern void rcu_advance_callbacks_rt(int cpu, int user);
+extern void rcu_check_callbacks_rt(int cpu, int user);
+extern void rcu_init_rt(void);
+extern int  rcu_needs_cpu_rt(int cpu);
+extern int  rcu_pending_rt(int cpu);
 struct softirq_action;
-
-extern void rcu_process_callbacks(struct softirq_action *unused);
+extern void rcu_process_callbacks_rt(struct softirq_action *unused);
 
 #endif /* __KERNEL__ */
 #endif /* __LINUX_RCUPREEMPT_H */

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diff -urpNa -X dontdiff linux-2.6.22.1-rt4/kernel/rcupdate.c linux-2.6.22.1-rt4-sched/kernel/rcupdate.c
@@ -51,6 +51,7 @@ struct rcu_synchronize {
 	struct completion completion;
 };
 
+DEFINE_PER_CPU(int, rcu_data_passed_quiesc);
 static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head);
 static atomic_t rcu_barrier_cpu_count;
 static DEFINE_MUTEX(rcu_barrier_mutex);

@@ -89,6 +90,21 @@ void synchronize_rcu(void)
 	wait_for_completion(&rcu.completion);
 }
 
+#ifdef CONFIG_PREEMPT_RCU
+
+/*
+ * Map synchronize_sched() to the classic RCU implementation.
+ */
+void __synchronize_sched(void)
+{
+	struct rcu_synchronize rcu;
+
+	init_completion(&rcu.completion);
+	call_rcu_classic(&rcu.head, wakeme_after_rcu);
+	wait_for_completion(&rcu.completion);
+}
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
+
 static void rcu_barrier_callback(struct rcu_head *notused)
 {
 	if (atomic_dec_and_test(&rcu_barrier_cpu_count))

@@ -122,10 +138,4 @@ void rcu_barrier(void)
 	mutex_unlock(&rcu_barrier_mutex);
 }
 EXPORT_SYMBOL_GPL(rcu_barrier);
-
-void __init rcu_init(void)
-{
-	__rcu_init();
-}
-
 EXPORT_SYMBOL_GPL(synchronize_rcu);

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