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>

diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c
index fb83326..dbeadb9 100644 (file)
--- a/arch/ia64/xen/time.c
+++ b/arch/ia64/xen/time.c
@@ -133,8 +133,7 @@ consider_steal_time(unsigned long new_itm)
                account_idle_ticks(blocked);
                run_local_timers();
 
-               if (rcu_pending(cpu))
-                       rcu_check_callbacks(cpu, user_mode(get_irq_regs()));
+               rcu_check_callbacks(cpu, user_mode(get_irq_regs()));
 
                scheduler_tick();
                run_posix_cpu_timers(p);

diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
index 6c9dd9c..aff4772 100644 (file)
--- a/include/linux/rcupreempt.h
+++ b/include/linux/rcupreempt.h
@@ -66,7 +66,6 @@ extern void call_rcu_sched(struct rcu_head *head,
 
 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_read_lock_bh()   { rcu_read_lock(); local_bh_disable(); }

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 8a0222c..c739d90 100644 (file)
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -33,7 +33,6 @@
 extern void rcu_sched_qs(int cpu);
 extern void rcu_bh_qs(int cpu);
 
-extern int rcu_pending(int cpu);
 extern int rcu_needs_cpu(int cpu);
 
 static inline void __rcu_read_lock(void)

diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 7d777c9..0053ce5 100644 (file)
--- 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 7c51508..4ce3adc 100644 (file)
--- 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 a7f07d5..a3d25f4 100644 (file)
--- 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);