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-rw-r--r--arch/i386/kernel/timers/timer_tsc.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/arch/i386/kernel/timers/timer_tsc.c b/arch/i386/kernel/timers/timer_tsc.c
index 47675bbbb316..7c86e3c5f1c1 100644
--- a/arch/i386/kernel/timers/timer_tsc.c
+++ b/arch/i386/kernel/timers/timer_tsc.c
@@ -45,6 +45,15 @@ static unsigned long last_tsc_high; /* msb 32 bits of Time Stamp Counter */
static unsigned long long monotonic_base;
static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
+/* Avoid compensating for lost ticks before TSCs are synched */
+static int detect_lost_ticks;
+static int __init start_lost_tick_compensation(void)
+{
+ detect_lost_ticks = 1;
+ return 0;
+}
+late_initcall(start_lost_tick_compensation);
+
/* convert from cycles(64bits) => nanoseconds (64bits)
* basic equation:
* ns = cycles / (freq / ns_per_sec)
@@ -196,7 +205,8 @@ static void mark_offset_tsc_hpet(void)
/* lost tick compensation */
offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
- if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))) {
+ if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))
+ && detect_lost_ticks) {
int lost_ticks = (offset - hpet_last) / hpet_tick;
jiffies_64 += lost_ticks;
}
@@ -421,7 +431,7 @@ static void mark_offset_tsc(void)
delta += delay_at_last_interrupt;
lost = delta/(1000000/HZ);
delay = delta%(1000000/HZ);
- if (lost >= 2) {
+ if (lost >= 2 && detect_lost_ticks) {
jiffies_64 += lost-1;
/* sanity check to ensure we're not always losing ticks */