sched/x86: Fix overflow in cyc2ns_offset

[linux-flexiantxendom0.git] / arch / x86 / kernel / tsc.c

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e58e0d1..9a987d4 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -620,7 +620,8 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 
        if (cpu_khz) {
                *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
-               *offset = ns_now - (tsc_now * *scale >> CYC2NS_SCALE_FACTOR);
+               *offset = ns_now - mult_frac(tsc_now, *scale,
+                                            (1UL << CYC2NS_SCALE_FACTOR));
        }
 
        sched_clock_idle_wakeup_event(0);