[S390] rework idle code

Whenever the cpu loads an enabled wait PSW it will appear as idle to the
underlying host system. The code in default_idle calls vtime_stop_cpu
which does the necessary voodoo to get the cpu time accounting right.
The udelay code just loads an enabled wait PSW. To correct this rework
the vtime_stop_cpu/vtime_start_cpu logic and move the difficult parts
to entry[64].S, vtime_stop_cpu can now be called from anywhere and
vtime_start_cpu is gone. The correction of the cpu time during wakeup
from an enabled wait PSW is done with a critical section in entry[64].S.
As vtime_start_cpu is gone, s390_idle_check can be removed as well.

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

1 files changed, 1 insertions, 6 deletions

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index e795933eb2c..78b3c149b8b 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -77,13 +77,8 @@ static void default_idle(void)
 		local_irq_enable();
 		return;
 	}
-	trace_hardirqs_on();
-	/* Don't trace preempt off for idle. */
-	stop_critical_timings();
-	/* Stop virtual timer and halt the cpu. */
+	/* Halt the cpu and keep track of cpu time accounting. */
 	vtime_stop_cpu();
-	/* Reenable preemption tracer. */
-	start_critical_timings();
 }
 
 void cpu_idle(void)