[S390] boot cputime accounting
Start the cpu time accounting very early to catch the cpu time spent
for the initial kernel setup. To make the output of /proc/uptime
match the sum of all cpu accounting values of the boot cpu reset
xtime and wall_to_monotonic to sane values based on the TOD clock.
The values set by timekeeping_init are off by up to a second.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 369ff02..6ded50d 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -253,32 +253,52 @@
*/
void __init time_init(void)
{
+ struct timespec ts;
+ unsigned long flags;
+ cycle_t now;
+
/* Reset time synchronization interfaces. */
etr_reset();
stp_reset();
- /* set xtime */
- tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime);
- set_normalized_timespec(&wall_to_monotonic,
- -xtime.tv_sec, -xtime.tv_nsec);
-
/* request the clock comparator external interrupt */
if (register_early_external_interrupt(0x1004,
clock_comparator_interrupt,
&ext_int_info_cc) != 0)
panic("Couldn't request external interrupt 0x1004");
- if (clocksource_register(&clocksource_tod) != 0)
- panic("Could not register TOD clock source");
-
/* request the timing alert external interrupt */
if (register_early_external_interrupt(0x1406,
timing_alert_interrupt,
&ext_int_etr_cc) != 0)
panic("Couldn't request external interrupt 0x1406");
+ if (clocksource_register(&clocksource_tod) != 0)
+ panic("Could not register TOD clock source");
+
+ /*
+ * The TOD clock is an accurate clock. The xtime should be
+ * initialized in a way that the difference between TOD and
+ * xtime is reasonably small. Too bad that timekeeping_init
+ * sets xtime.tv_nsec to zero. In addition the clock source
+ * change from the jiffies clock source to the TOD clock
+ * source add another error of up to 1/HZ second. The same
+ * function sets wall_to_monotonic to a value that is too
+ * small for /proc/uptime to be accurate.
+ * Reset xtime and wall_to_monotonic to sane values.
+ */
+ write_seqlock_irqsave(&xtime_lock, flags);
+ now = get_clock();
+ tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
+ clocksource_tod.cycle_last = now;
+ clocksource_tod.raw_time = xtime;
+ tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
+ set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
/* Enable TOD clock interrupts on the boot cpu. */
init_cpu_timer();
+
/* Enable cpu timer interrupts on the boot cpu. */
vtime_init();
}