[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>

1 files changed, 16 insertions, 0 deletions

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.