sched/accounting, proc: Fix /proc/stat interrupts sum

Commit 3292beb ("sched/accounting: Change cpustat fields to an array")
deleted the code which provides us with the sum of all interrupts in the
system, causing vmstat to report zero interrupts occuring in the system.

Fix this by restoring the code.

Signed-off-by: Russell King <[email protected]>
Tested-by: Russell King <[email protected]> # [on ARM]
Tested-by: Tony Luck <[email protected]>
Tested-by: Steven Rostedt <[email protected]>
Cc: Glauber Costa <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Paul Tuner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

fs/proc/stat.c

@@ -77,6 +77,8 @@ static int show_stat(struct seq_file *p, void *v)
 		steal += kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
 		guest += kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
 		guest_nice += kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
+		sum += kstat_cpu_irqs_sum(i);
+		sum += arch_irq_stat_cpu(i);
 
 		for (j = 0; j < NR_SOFTIRQS; j++) {
 			unsigned int softirq_stat = kstat_softirqs_cpu(j, i);