[PATCH] rcu: join rcu_ctrlblk and rcu_state

This patch moves rcu_state into the rcu_ctrlblk. I think there
are no reasons why we should have 2 different variables to control
rcu state. Every user of rcu_state has also "rcu_ctrlblk *rcp" in
the parameter list.

Signed-off-by: Oleg Nesterov <[e-mail]>
Acked-by: Paul E. McKenney <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/rcupdate.h

···
 	long	cur;		/* Current batch number.                      */
 	long	completed;	/* Number of the last completed batch         */
 	int	next_pending;	/* Is the next batch already waiting?         */
+
+	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 ? */

kernel/rcupdate.c

···
 #include <linux/cpu.h>
 
 /* Definition for rcupdate control block. */
-struct rcu_ctrlblk rcu_ctrlblk = 
-	{ .cur = -300, .completed = -300 };
-struct rcu_ctrlblk rcu_bh_ctrlblk =
-	{ .cur = -300, .completed = -300 };
-
-/* Bookkeeping of the progress of the grace period */
-struct rcu_state {
-	spinlock_t	lock; /* Guard this struct and writes to rcu_ctrlblk */
-	cpumask_t	cpumask; /* CPUs that need to switch in order    */
-	                              /* for current batch to proceed.        */
+struct rcu_ctrlblk rcu_ctrlblk = {
+	.cur = -300,
+	.completed = -300,
+	.lock = SPIN_LOCK_UNLOCKED,
+	.cpumask = CPU_MASK_NONE,
 };
-
-static struct rcu_state rcu_state ____cacheline_internodealigned_in_smp =
-	  {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
-static struct rcu_state rcu_bh_state ____cacheline_internodealigned_in_smp =
-	  {.lock = SPIN_LOCK_UNLOCKED, .cpumask = CPU_MASK_NONE };
+struct rcu_ctrlblk rcu_bh_ctrlblk = {
+	.cur = -300,
+	.completed = -300,
+	.lock = SPIN_LOCK_UNLOCKED,
+	.cpumask = CPU_MASK_NONE,
+};
 
 DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
 DEFINE_PER_CPU(struct rcu_data, rcu_bh_data) = { 0L };
···
  *   This is done by rcu_start_batch. The start is not broadcasted to
  *   all cpus, they must pick this up by comparing rcp->cur with
  *   rdp->quiescbatch. All cpus are recorded  in the
- *   rcu_state.cpumask bitmap.
+ *   rcu_ctrlblk.cpumask bitmap.
  * - All cpus must go through a quiescent state.
  *   Since the start of the grace period is not broadcasted, at least two
  *   calls to rcu_check_quiescent_state are required:
  *   The first call just notices that a new grace period is running. The
  *   following calls check if there was a quiescent state since the beginning
- *   of the grace period. If so, it updates rcu_state.cpumask. If
+ *   of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
  *   the bitmap is empty, then the grace period is completed.
  *   rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
  *   period (if necessary).
···
 /*
  * Register a new batch of callbacks, and start it up if there is currently no
  * active batch and the batch to be registered has not already occurred.
- * Caller must hold rcu_state.lock.
+ * Caller must hold rcu_ctrlblk.lock.
  */
-static void rcu_start_batch(struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
+static void rcu_start_batch(struct rcu_ctrlblk *rcp)
 {
 	if (rcp->next_pending &&
 			rcp->completed == rcp->cur) {
···
 		/*
 		 * Accessing nohz_cpu_mask before incrementing rcp->cur needs a
 		 * Barrier  Otherwise it can cause tickless idle CPUs to be
-		 * included in rsp->cpumask, which will extend graceperiods
+		 * included in rcp->cpumask, which will extend graceperiods
 		 * unnecessarily.
 		 */
 		smp_mb();
-		cpus_andnot(rsp->cpumask, cpu_online_map, nohz_cpu_mask);
+		cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
 
 	}
 }
···
  * Clear it from the cpu mask and complete the grace period if it was the last
  * cpu. Start another grace period if someone has further entries pending
  */
-static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp, struct rcu_state *rsp)
+static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
 {
-	cpu_clear(cpu, rsp->cpumask);
-	if (cpus_empty(rsp->cpumask)) {
+	cpu_clear(cpu, rcp->cpumask);
+	if (cpus_empty(rcp->cpumask)) {
 		/* batch completed ! */
 		rcp->completed = rcp->cur;
-		rcu_start_batch(rcp, rsp);
+		rcu_start_batch(rcp);
 	}
 }
 
···
  * quiescent cycle, then indicate that it has done so.
  */
 static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
-			struct rcu_state *rsp, struct rcu_data *rdp)
+					struct rcu_data *rdp)
 {
 	if (rdp->quiescbatch != rcp->cur) {
 		/* start new grace period: */
···
 		return;
 	rdp->qs_pending = 0;
 
-	spin_lock(&rsp->lock);
+	spin_lock(&rcp->lock);
 	/*
 	 * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
 	 * during cpu startup. Ignore the quiescent state.
 	 */
 	if (likely(rdp->quiescbatch == rcp->cur))
-		cpu_quiet(rdp->cpu, rcp, rsp);
+		cpu_quiet(rdp->cpu, rcp);
 
-	spin_unlock(&rsp->lock);
+	spin_unlock(&rcp->lock);
 }
 
 
···
 }
 
 static void __rcu_offline_cpu(struct rcu_data *this_rdp,
-	struct rcu_ctrlblk *rcp, struct rcu_state *rsp, struct rcu_data *rdp)
+				struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
 {
 	/* if the cpu going offline owns the grace period
 	 * we can block indefinitely waiting for it, so flush
 	 * it here
 	 */
-	spin_lock_bh(&rsp->lock);
+	spin_lock_bh(&rcp->lock);
 	if (rcp->cur != rcp->completed)
-		cpu_quiet(rdp->cpu, rcp, rsp);
-	spin_unlock_bh(&rsp->lock);
+		cpu_quiet(rdp->cpu, rcp);
+	spin_unlock_bh(&rcp->lock);
 	rcu_move_batch(this_rdp, rdp->curlist, rdp->curtail);
 	rcu_move_batch(this_rdp, rdp->nxtlist, rdp->nxttail);
 
···
 	struct rcu_data *this_rdp = &get_cpu_var(rcu_data);
 	struct rcu_data *this_bh_rdp = &get_cpu_var(rcu_bh_data);
 
-	__rcu_offline_cpu(this_rdp, &rcu_ctrlblk, &rcu_state,
+	__rcu_offline_cpu(this_rdp, &rcu_ctrlblk,
 					&per_cpu(rcu_data, cpu));
-	__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk, &rcu_bh_state,
+	__rcu_offline_cpu(this_bh_rdp, &rcu_bh_ctrlblk,
 					&per_cpu(rcu_bh_data, cpu));
 	put_cpu_var(rcu_data);
 	put_cpu_var(rcu_bh_data);
···
  * This does the RCU processing work from tasklet context. 
  */
 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
-			struct rcu_state *rsp, struct rcu_data *rdp)
+					struct rcu_data *rdp)
 {
 	if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
 		*rdp->donetail = rdp->curlist;
···
 
 		if (!rcp->next_pending) {
 			/* and start it/schedule start if it's a new batch */
-			spin_lock(&rsp->lock);
+			spin_lock(&rcp->lock);
 			rcp->next_pending = 1;
-			rcu_start_batch(rcp, rsp);
-			spin_unlock(&rsp->lock);
+			rcu_start_batch(rcp);
+			spin_unlock(&rcp->lock);
 		}
 	} else {
 		local_irq_enable();
 	}
-	rcu_check_quiescent_state(rcp, rsp, rdp);
+	rcu_check_quiescent_state(rcp, rdp);
 	if (rdp->donelist)
 		rcu_do_batch(rdp);
 }
 
 static void rcu_process_callbacks(unsigned long unused)
 {
-	__rcu_process_callbacks(&rcu_ctrlblk, &rcu_state,
-				&__get_cpu_var(rcu_data));
-	__rcu_process_callbacks(&rcu_bh_ctrlblk, &rcu_bh_state,
-				&__get_cpu_var(rcu_bh_data));
+	__rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
+	__rcu_process_callbacks(&rcu_bh_ctrlblk, &__get_cpu_var(rcu_bh_data));
 }
 
 static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)