rcu: Remove "cpu" argument to rcu_check_callbacks()

The "cpu" argument was kept around on the off-chance that RCU might
offload scheduler-clock interrupts.  However, this offload approach
has been replaced by NO_HZ_FULL, which offloads -all- RCU processing
from qualifying CPUs.  It is therefore time to remove the "cpu" argument
to rcu_check_callbacks(), which this commit does.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

include/linux/rcupdate.h

@@ -260,7 +260,7 @@ static inline int rcu_preempt_depth(void)
 void rcu_init(void);
 void rcu_sched_qs(void);
 void rcu_bh_qs(void);
-void rcu_check_callbacks(int cpu, int user);
+void rcu_check_callbacks(int user);
 struct notifier_block;
 void rcu_idle_enter(void);
 void rcu_idle_exit(void);

kernel/rcu/tiny.c

@@ -247,7 +247,7 @@ void rcu_bh_qs(void)
  * be called from hardirq context.  It is normally called from the
  * scheduling-clock interrupt.
  */
-void rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int user)
 {
 	RCU_TRACE(check_cpu_stalls());
 	if (user || rcu_is_cpu_rrupt_from_idle())

kernel/rcu/tree.c

@@ -2388,7 +2388,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
  * invoked from the scheduling-clock interrupt.  If rcu_pending returns
  * false, there is no point in invoking rcu_check_callbacks().
  */
-void rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int user)
 {
 	trace_rcu_utilization(TPS("Start scheduler-tick"));
 	increment_cpu_stall_ticks();
@@ -2420,8 +2420,8 @@ void rcu_check_callbacks(int cpu, int user)
 
 		rcu_bh_qs();
 	}
-	rcu_preempt_check_callbacks(cpu);
-	if (rcu_pending(cpu))
+	rcu_preempt_check_callbacks(smp_processor_id());
+	if (rcu_pending(smp_processor_id()))
 		invoke_rcu_core();
 	if (user)
 		rcu_note_voluntary_context_switch(current);

kernel/time/timer.c

@@ -1377,12 +1377,11 @@ unsigned long get_next_timer_interrupt(unsigned long now)
 void update_process_times(int user_tick)
 {
 	struct task_struct *p = current;
-	int cpu = smp_processor_id();
 
 	/* Note: this timer irq context must be accounted for as well. */
 	account_process_tick(p, user_tick);
 	run_local_timers();
-	rcu_check_callbacks(cpu, user_tick);
+	rcu_check_callbacks(user_tick);
 #ifdef CONFIG_IRQ_WORK
 	if (in_irq())
 		irq_work_tick();