1 files changed, 8 insertions, 19 deletions

diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index a326f27d7f09..396f7b9dccc9 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -14,11 +14,12 @@
 #include <linux/syscore_ops.h>
 #include <linux/timer.h>
 #include <linux/sched_clock.h>
+#include <linux/seqlock.h>
 
 struct clock_data {
         u64 epoch_ns;
         u32 epoch_cyc;
-        u32 epoch_cyc_copy;
+        seqcount_t seq;
         unsigned long rate;
         u32 mult;
         u32 shift;
@@ -54,23 +55,16 @@ static unsigned long long notrace sched_clock_32(void)
         u64 epoch_ns;
         u32 epoch_cyc;
         u32 cyc;
+        unsigned long seq;
 
         if (cd.suspended)
                 return cd.epoch_ns;
 
-        /*
-         * Load the epoch_cyc and epoch_ns atomically.  We do this by
-         * ensuring that we always write epoch_cyc, epoch_ns and
-         * epoch_cyc_copy in strict order, and read them in strict order.
-         * If epoch_cyc and epoch_cyc_copy are not equal, then we're in
-         * the middle of an update, and we should repeat the load.
-         */
         do {
+                seq = read_seqcount_begin(&cd.seq);
                 epoch_cyc = cd.epoch_cyc;
-                smp_rmb();
                 epoch_ns = cd.epoch_ns;
-                smp_rmb();
-        } while (epoch_cyc != cd.epoch_cyc_copy);
+        } while (read_seqcount_retry(&cd.seq, seq));
 
         cyc = read_sched_clock();
         cyc = (cyc - epoch_cyc) & sched_clock_mask;
@@ -90,16 +84,12 @@ static void notrace update_sched_clock(void)
         ns = cd.epoch_ns +
                 cyc_to_ns((cyc - cd.epoch_cyc) & sched_clock_mask,
                           cd.mult, cd.shift);
-        /*
-         * Write epoch_cyc and epoch_ns in a way that the update is
-         * detectable in cyc_to_fixed_sched_clock().
-         */
+
         raw_local_irq_save(flags);
-        cd.epoch_cyc_copy = cyc;
-        smp_wmb();
+        write_seqcount_begin(&cd.seq);
         cd.epoch_ns = ns;
-        smp_wmb();
         cd.epoch_cyc = cyc;
+        write_seqcount_end(&cd.seq);
         raw_local_irq_restore(flags);
 }
 
@@ -195,7 +185,6 @@ static int sched_clock_suspend(void)
 static void sched_clock_resume(void)
 {
         cd.epoch_cyc = read_sched_clock();
-        cd.epoch_cyc_copy = cd.epoch_cyc;
         cd.suspended = false;
 }