[S390] /proc/stat idle field for idle cpus

The cpu idle field in the output of /proc/stat is too small for cpus
that have been idle for more than a tick. Add the architecture hook
arch_idle_time that allows to add the not accounted idle time of a
sleeping cpu without waking the cpu.

The s390 implementation of arch_idle_time uses the already existing
s390_idle_data per_cpu variable to find the sleep time of a neighboring
idle cpu.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

3 files changed, 25 insertions, 0 deletions

diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 95b0f7db3c69..941384fbd39c 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -174,4 +174,8 @@ cputime64_to_clock_t(cputime64_t cputime)
        return __div(cputime, 4096000000ULL / USER_HZ);
 }
 
+cputime64_t s390_get_idle_time(int cpu);
+
+#define arch_idle_time(cpu) s390_get_idle_time(cpu)
+
 #endif /* _S390_CPUTIME_H */
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index 38ea92ff04f9..c87f59bd8246 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -240,6 +240,22 @@ void vtime_stop_cpu(void)
         }
 }
 
+cputime64_t s390_get_idle_time(int cpu)
+{
+        struct s390_idle_data *idle;
+        unsigned long long now, idle_time, idle_enter;
+
+        idle = &per_cpu(s390_idle, cpu);
+        spin_lock(&idle->lock);
+        now = get_clock();
+        idle_time = 0;
+        idle_enter = idle->idle_enter;
+        if (idle_enter != 0ULL && idle_enter < now)
+                idle_time = now - idle_enter;
+        spin_unlock(&idle->lock);
+        return idle_time;
+}
+
 /*
  * Sorted add to a list. List is linear searched until first bigger
  * element is found.
diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index f75efa22df5e..81e4eb60972e 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -18,6 +18,9 @@
 #ifndef arch_irq_stat
 #define arch_irq_stat() 0
 #endif
+#ifndef arch_idle_time
+#define arch_idle_time(cpu) 0
+#endif
 
 static int show_stat(struct seq_file *p, void *v)
 {
@@ -40,6 +43,7 @@ static int show_stat(struct seq_file *p, void *v)
                 nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice);
                 system = cputime64_add(system, kstat_cpu(i).cpustat.system);
                 idle = cputime64_add(idle, kstat_cpu(i).cpustat.idle);
+                idle = cputime64_add(idle, arch_idle_time(i));
                 iowait = cputime64_add(iowait, kstat_cpu(i).cpustat.iowait);
                 irq = cputime64_add(irq, kstat_cpu(i).cpustat.irq);
                 softirq = cputime64_add(softirq, kstat_cpu(i).cpustat.softirq);
@@ -69,6 +73,7 @@ static int show_stat(struct seq_file *p, void *v)
                 nice = kstat_cpu(i).cpustat.nice;
                 system = kstat_cpu(i).cpustat.system;
                 idle = kstat_cpu(i).cpustat.idle;
+                idle = cputime64_add(idle, arch_idle_time(i));
                 iowait = kstat_cpu(i).cpustat.iowait;
                 irq = kstat_cpu(i).cpustat.irq;
                 softirq = kstat_cpu(i).cpustat.softirq;