[PATCH] rcu: clean up code

Avoids per_cpu calculations and also prepares for call_rcu_bh().

At OLS, Rusty had suggested getting rid of many per_cpu() calculations in RCU
code and making the code simpler.  I had already done that for the rcu-softirq
patch earlier, so I am splitting that into two patch.  This first patch cleans
up the macros and uses pointers to the rcu per-cpu data directly to manipulate
the callback queues.  This is useful for the call-rcu-bh patch (to follow)
which introduces a new RCU mechanism - call_rcu_bh().  Both generic and
softirq rcu can then use the same code, they work different global and percpu
data.
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/rcupdate.h

@@ -101,47 +101,51 @@ struct rcu_data {
         struct rcu_head **curtail;
         struct rcu_head *donelist;
         struct rcu_head **donetail;
+	int cpu;
 };
 
 DECLARE_PER_CPU(struct rcu_data, rcu_data);
 extern struct rcu_ctrlblk rcu_ctrlblk;
 
-#define RCU_quiescbatch(cpu)	(per_cpu(rcu_data, (cpu)).quiescbatch)
-#define RCU_qsctr(cpu) 		(per_cpu(rcu_data, (cpu)).qsctr)
-#define RCU_last_qsctr(cpu) 	(per_cpu(rcu_data, (cpu)).last_qsctr)
-#define RCU_qs_pending(cpu)	(per_cpu(rcu_data, (cpu)).qs_pending)
-#define RCU_batch(cpu) 		(per_cpu(rcu_data, (cpu)).batch)
-#define RCU_nxtlist(cpu) 	(per_cpu(rcu_data, (cpu)).nxtlist)
-#define RCU_curlist(cpu) 	(per_cpu(rcu_data, (cpu)).curlist)
-#define RCU_nxttail(cpu) 	(per_cpu(rcu_data, (cpu)).nxttail)
-#define RCU_curtail(cpu) 	(per_cpu(rcu_data, (cpu)).curtail)
-#define RCU_donelist(cpu) 	(per_cpu(rcu_data, (cpu)).donelist)
-#define RCU_donetail(cpu) 	(per_cpu(rcu_data, (cpu)).donetail)
+/*
+ * Increment the quiscent state counter.
+ */
+static inline void rcu_qsctr_inc(int cpu)
+{
+	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+	rdp->qsctr++;
+}
 
-static inline int rcu_pending(int cpu) 
+static inline int __rcu_pending(struct rcu_ctrlblk *rcp,
+						struct rcu_data *rdp)
 {
 	/* This cpu has pending rcu entries and the grace period
 	 * for them has completed.
 	 */
-	if (RCU_curlist(cpu) &&
-		  !rcu_batch_before(rcu_ctrlblk.completed,RCU_batch(cpu)))
+	if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
 		return 1;
 
 	/* This cpu has no pending entries, but there are new entries */
-	if (!RCU_curlist(cpu) && RCU_nxtlist(cpu))
+	if (!rdp->curlist && rdp->nxtlist)
 		return 1;
 
-	if (RCU_donelist(cpu))
+	/* This cpu has finished callbacks to invoke */
+	if (rdp->donelist)
 		return 1;
 
 	/* The rcu core waits for a quiescent state from the cpu */
-	if (RCU_quiescbatch(cpu) != rcu_ctrlblk.cur || RCU_qs_pending(cpu))
+	if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
 		return 1;
 
 	/* nothing to do */
 	return 0;
 }
 
+static inline int rcu_pending(int cpu)
+{
+	return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu));
+}
+
 #define rcu_read_lock()		preempt_disable()
 #define rcu_read_unlock()	preempt_enable()
 

kernel/sched.c

@@ -2287,7 +2287,7 @@ asmlinkage void __sched schedule(void)
 switch_tasks:
 	prefetch(next);
 	clear_tsk_need_resched(prev);
-	RCU_qsctr(task_cpu(prev))++;
+	rcu_qsctr_inc(task_cpu(prev));
 
 	prev->sleep_avg -= run_time;
 	if ((long)prev->sleep_avg <= 0) {