Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[sfrench/cifs-2.6.git] / arch / x86 / kernel / tsc.c

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index d57de05dc43093e0831ebb544a2baddf3d72f184..3e1c057e98fe039325eed2056d8960fa52f023c4 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -384,13 +384,13 @@ unsigned long native_calibrate_tsc(void)
 {
        u64 tsc1, tsc2, delta, ref1, ref2;
        unsigned long tsc_pit_min = ULONG_MAX, tsc_ref_min = ULONG_MAX;
-       unsigned long flags, latch, ms, fast_calibrate, tsc_khz;
+       unsigned long flags, latch, ms, fast_calibrate, hv_tsc_khz;
        int hpet = is_hpet_enabled(), i, loopmin;
 
-       tsc_khz = get_hypervisor_tsc_freq();
-       if (tsc_khz) {
+       hv_tsc_khz = get_hypervisor_tsc_freq();
+       if (hv_tsc_khz) {
                printk(KERN_INFO "TSC: Frequency read from the hypervisor\n");
-               return tsc_khz;
+               return hv_tsc_khz;
        }
 
        local_irq_save(flags);
@@ -710,7 +710,16 @@ static cycle_t read_tsc(struct clocksource *cs)
 #ifdef CONFIG_X86_64
 static cycle_t __vsyscall_fn vread_tsc(void)
 {
-       cycle_t ret = (cycle_t)vget_cycles();
+       cycle_t ret;
+
+       /*
+        * Surround the RDTSC by barriers, to make sure it's not
+        * speculated to outside the seqlock critical section and
+        * does not cause time warps:
+        */
+       rdtsc_barrier();
+       ret = (cycle_t)vget_cycles();
+       rdtsc_barrier();
 
        return ret >= __vsyscall_gtod_data.clock.cycle_last ?
                ret : __vsyscall_gtod_data.clock.cycle_last;