[PATCH] Make kstat_this_cpu in terms of __get_cpu_var and use it

kstat_this_cpu() is defined in terms of per_cpu instead of __get_cpu_var.

This patch changes that, and uses it everywhere appropriate.  The sched.c
change puts it in a local variable, which helps gcc generate better code.

arch/i386/kernel/irq.c

@@ -416,7 +416,6 @@ asmlinkage unsigned int do_IRQ(struct pt_regs regs)
 	 * handled by some other CPU. (or is disabled)
 	 */
 	int irq = regs.orig_eax & 0xff; /* high bits used in ret_from_ code  */
-	int cpu = smp_processor_id();
 	irq_desc_t *desc = irq_desc + irq;
 	struct irqaction * action;
 	unsigned int status;
@@ -437,7 +436,7 @@ asmlinkage unsigned int do_IRQ(struct pt_regs regs)
 		}
 	}
 #endif
-	kstat_cpu(cpu).irqs[irq]++;
+	kstat_this_cpu.irqs[irq]++;
 	spin_lock(&desc->lock);
 	desc->handler->ack(irq);
 	/*

include/linux/kernel_stat.h

@@ -31,7 +31,8 @@ struct kernel_stat {
 DECLARE_PER_CPU(struct kernel_stat, kstat);
 
 #define kstat_cpu(cpu)	per_cpu(kstat, cpu)
-#define kstat_this_cpu	kstat_cpu(smp_processor_id())
+/* Must have preemption disabled for this to be meaningful. */
+#define kstat_this_cpu	__get_cpu_var(kstat)
 
 extern unsigned long nr_context_switches(void);
 

kernel/sched.c

@@ -1175,6 +1175,7 @@ DEFINE_PER_CPU(struct kernel_stat, kstat) = { { 0 } };
 void scheduler_tick(int user_ticks, int sys_ticks)
 {
 	int cpu = smp_processor_id();
+	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
 	runqueue_t *rq = this_rq();
 	task_t *p = current;
 
@@ -1184,19 +1185,19 @@ void scheduler_tick(int user_ticks, int sys_ticks)
 	if (p == rq->idle) {
 		/* note: this timer irq context must be accounted for as well */
 		if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET)
-			kstat_cpu(cpu).cpustat.system += sys_ticks;
+			cpustat->system += sys_ticks;
 		else if (atomic_read(&rq->nr_iowait) > 0)
-			kstat_cpu(cpu).cpustat.iowait += sys_ticks;
+			cpustat->iowait += sys_ticks;
 		else
-			kstat_cpu(cpu).cpustat.idle += sys_ticks;
+			cpustat->idle += sys_ticks;
 		rebalance_tick(rq, 1);
 		return;
 	}
 	if (TASK_NICE(p) > 0)
-		kstat_cpu(cpu).cpustat.nice += user_ticks;
+		cpustat->nice += user_ticks;
 	else
-		kstat_cpu(cpu).cpustat.user += user_ticks;
-	kstat_cpu(cpu).cpustat.system += sys_ticks;
+		cpustat->user += user_ticks;
+	cpustat->system += sys_ticks;
 
 	/* Task might have expired already, but not scheduled off yet */
 	if (p->array != rq->active) {