rcu: Simplify rcu_pending()/rcu_check_callbacks() API

All calls from outside RCU are of the form:

	if (rcu_pending(cpu))
		rcu_check_callbacks(cpu, user);

This is silly, instead we put a call to rcu_pending() in
rcu_check_callbacks(), and then make the outside calls be to
rcu_check_callbacks().  This cuts down on the code a bit and
also gives the compiler a better chance of optimizing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josht@linux.vnet.ibm.com
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
LKML-Reference: <125097461311-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 13 insertions, 5 deletions

diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 7d777c9f394c..0053ce56e326 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -159,6 +159,8 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched
         .dynticks = 1,
 };
 
+static int rcu_pending(int cpu);
+
 void rcu_sched_qs(int cpu)
 {
         struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
@@ -961,7 +963,10 @@ static void rcu_check_mb(int cpu)
 void rcu_check_callbacks(int cpu, int user)
 {
         unsigned long flags;
-        struct rcu_data *rdp = RCU_DATA_CPU(cpu);
+        struct rcu_data *rdp;
+
+        if (!rcu_pending(cpu))
+                return; /* if nothing for RCU to do. */
 
         /*
          * If this CPU took its interrupt from user mode or from the
@@ -976,6 +981,7 @@ void rcu_check_callbacks(int cpu, int user)
          * CPUs to happen after any such write.
          */
 
+        rdp = RCU_DATA_CPU(cpu);
         if (user ||
             (idle_cpu(cpu) && !in_softirq() &&
              hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
@@ -1382,7 +1388,7 @@ int rcu_needs_cpu(int cpu)
                 rdp->waitschedlist != NULL);
 }
 
-int rcu_pending(int cpu)
+static int rcu_pending(int cpu)
 {
         struct rcu_data *rdp = RCU_DATA_CPU(cpu);
 
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7c515082ae84..4ce3adcfa94d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -111,6 +111,7 @@ static int qhimark = 10000;	/* If this many pending, ignore blimit. */
 static int qlowmark = 100;      /* Once only this many pending, use blimit. */
 
 static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
+static int rcu_pending(int cpu);
 
 /*
  * Return the number of RCU-sched batches processed thus far for debug & stats.
@@ -974,6 +975,8 @@ static void rcu_do_batch(struct rcu_data *rdp)
  */
 void rcu_check_callbacks(int cpu, int user)
 {
+        if (!rcu_pending(cpu))
+                return; /* if nothing for RCU to do. */
         if (user ||
             (idle_cpu(cpu) && rcu_scheduler_active &&
              !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
@@ -1329,7 +1332,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
  * by the current CPU, returning 1 if so.  This function is part of the
  * RCU implementation; it is -not- an exported member of the RCU API.
  */
-int rcu_pending(int cpu)
+static int rcu_pending(int cpu)
 {
         return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
                __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu));
diff --git a/kernel/timer.c b/kernel/timer.c
index a7f07d5a6241..a3d25f415019 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1156,8 +1156,7 @@ void update_process_times(int user_tick)
         /* Note: this timer irq context must be accounted for as well. */
         account_process_tick(p, user_tick);
         run_local_timers();
-        if (rcu_pending(cpu))
-                rcu_check_callbacks(cpu, user_tick);
+        rcu_check_callbacks(cpu, user_tick);
         printk_tick();
         scheduler_tick();
         run_posix_cpu_timers(p);