Linux-libre 4.3.2-gnu

1 files changed, 6 insertions, 8 deletions

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index dd8d0791d..78083bf23 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -39,16 +39,15 @@ static cycles_t max_warp;
 static int nr_warps;
 
 /*
- * TSC-warp measurement loop running on both CPUs:
+ * TSC-warp measurement loop running on both CPUs.  This is not called
+ * if there is no TSC.
  */
 static void check_tsc_warp(unsigned int timeout)
 {
 	cycles_t start, now, prev, end;
 	int i;
 
-	rdtsc_barrier();
-	start = get_cycles();
-	rdtsc_barrier();
+	start = rdtsc_ordered();
 	/*
 	 * The measurement runs for 'timeout' msecs:
 	 */
@@ -63,9 +62,7 @@ static void check_tsc_warp(unsigned int timeout)
 		 */
 		arch_spin_lock(&sync_lock);
 		prev = last_tsc;
-		rdtsc_barrier();
-		now = get_cycles();
-		rdtsc_barrier();
+		now = rdtsc_ordered();
 		last_tsc = now;
 		arch_spin_unlock(&sync_lock);
 
@@ -126,7 +123,7 @@ void check_tsc_sync_source(int cpu)
 
 	/*
 	 * No need to check if we already know that the TSC is not
-	 * synchronized:
+	 * synchronized or if we have no TSC.
 	 */
 	if (unsynchronized_tsc())
 		return;
@@ -190,6 +187,7 @@ void check_tsc_sync_target(void)
 {
 	int cpus = 2;
 
+	/* Also aborts if there is no TSC. */
 	if (unsynchronized_tsc() || tsc_clocksource_reliable)
 		return;