Reduce the number of while-loop iterations (from two to one in the most
common situation)
Signed-off-by: Arjan Koers <0h61vkll2ly8@xxxxxxxxxx>
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index bab3b9e..995d479 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -126,7 +126,7 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
struct pvclock_shadow_time shadow;
unsigned version;
cycle_t ret, offset;
- u64 last;
+ u64 last, save;
do {
version = pvclock_get_time_values(&shadow, src);
@@ -158,8 +158,9 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
do {
if (ret < last)
return last;
+ save = last;
last = atomic64_cmpxchg(&last_value, last, ret);
- } while (unlikely(last != ret));
+ } while (unlikely(last != save));
return ret;
}
--
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