irq, fs/proc: replace loop with nr_irqs for proc/stat

Replace another nr_irqs loop to avoid the allocation of all sparse
irq entries - use for_each_irq_desc instead.

v2: make sure arch without GENERIC_HARDIRQS works too

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

fs/proc/proc_misc.c

@@ -30,6 +30,7 @@
 #include <linux/mm.h>
 #include <linux/mmzone.h>
 #include <linux/pagemap.h>
+#include <linux/irq.h>
 #include <linux/interrupt.h>
 #include <linux/swap.h>
 #include <linux/slab.h>
@@ -501,17 +502,16 @@ static const struct file_operations proc_vmalloc_operations = {
 
 static int show_stat(struct seq_file *p, void *v)
 {
-	int i;
+	int i, j;
 	unsigned long jif;
 	cputime64_t user, nice, system, idle, iowait, irq, softirq, steal;
 	cputime64_t guest;
 	u64 sum = 0;
 	struct timespec boottime;
-	unsigned int *per_irq_sum;
-
-	per_irq_sum = kzalloc(sizeof(unsigned int)*nr_irqs, GFP_KERNEL);
-	if (!per_irq_sum)
-		return -ENOMEM;
+	unsigned int per_irq_sum;
+#ifdef CONFIG_GENERIC_HARDIRQS
+	struct irq_desc *desc;
+#endif
 
 	user = nice = system = idle = iowait =
 		irq = softirq = steal = cputime64_zero;
@@ -520,8 +520,6 @@ static int show_stat(struct seq_file *p, void *v)
 	jif = boottime.tv_sec;
 
 	for_each_possible_cpu(i) {
-		int j;
-
 		user = cputime64_add(user, kstat_cpu(i).cpustat.user);
 		nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice);
 		system = cputime64_add(system, kstat_cpu(i).cpustat.system);
@@ -531,10 +529,12 @@ static int show_stat(struct seq_file *p, void *v)
 		softirq = cputime64_add(softirq, kstat_cpu(i).cpustat.softirq);
 		steal = cputime64_add(steal, kstat_cpu(i).cpustat.steal);
 		guest = cputime64_add(guest, kstat_cpu(i).cpustat.guest);
-		for (j = 0; j < nr_irqs; j++) {
-			unsigned int temp = kstat_irqs_cpu(j, i);
+		for_each_irq_desc(j, desc)
+		{
+			unsigned int temp;
+
+			temp = kstat_irqs_cpu(j, i);
 			sum += temp;
-			per_irq_sum[j] += temp;
 		}
 		sum += arch_irq_stat_cpu(i);
 	}
@@ -577,8 +577,23 @@ static int show_stat(struct seq_file *p, void *v)
 	}
 	seq_printf(p, "intr %llu", (unsigned long long)sum);
 
-	for (i = 0; i < nr_irqs; i++)
-		seq_printf(p, " %u", per_irq_sum[i]);
+	/* sum again ? it could be updated? */
+	for_each_irq_desc(j, desc)
+	{
+		per_irq_sum = 0;
+		for_each_possible_cpu(i) {
+			unsigned int temp;
+
+			temp = kstat_irqs_cpu(j, i);
+			per_irq_sum += temp;
+		}
+
+#ifdef CONFIG_HAVE_SPARSE_IRQ
+		seq_printf(p, " %u:%u", j, per_irq_sum);
+#else
+		seq_printf(p, " %u", per_irq_sum);
+#endif
+	}
 
 	seq_printf(p,
 		"\nctxt %llu\n"
@@ -592,7 +607,6 @@ static int show_stat(struct seq_file *p, void *v)
 		nr_running(),
 		nr_iowait());
 
-	kfree(per_irq_sum);
 	return 0;
 }
 

include/linux/interrupt.h

@@ -17,6 +17,11 @@
 
 extern int nr_irqs;
 
+#ifndef CONFIG_GENERIC_HARDIRQS
+#define for_each_irq_desc(irq, desc)		\
+	for (irq = 0; irq < nr_irqs; irq++)
+#endif
+
 /*
  * These correspond to the IORESOURCE_IRQ_* defines in
  * linux/ioport.h to select the interrupt line behaviour.  When