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-rw-r--r--arch/s390/kernel/time.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index ee9fd7b8592..e1ad464b6f2 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -747,6 +747,7 @@ static void etr_adjust_time(unsigned long long clock, unsigned long long delay)
}
}
+#ifdef CONFIG_SMP
static void etr_sync_cpu_start(void *dummy)
{
int *in_sync = dummy;
@@ -758,8 +759,14 @@ static void etr_sync_cpu_start(void *dummy)
* __udelay will stop the cpu on an enabled wait psw until the
* TOD is running again.
*/
- while (*in_sync == 0)
+ while (*in_sync == 0) {
__udelay(1);
+ /*
+ * A different cpu changes *in_sync. Therefore use
+ * barrier() to force memory access.
+ */
+ barrier();
+ }
if (*in_sync != 1)
/* Didn't work. Clear per-cpu in sync bit again. */
etr_disable_sync_clock(NULL);
@@ -773,6 +780,7 @@ static void etr_sync_cpu_start(void *dummy)
static void etr_sync_cpu_end(void *dummy)
{
}
+#endif /* CONFIG_SMP */
/*
* Sync the TOD clock using the port refered to by aibp. This port