crypto: wait for a full jiffy in do_xor_speed

In the existing do_xor_speed(), there is no guarantee that we actually
run do_2() for a full jiffy. We get the current jiffy, then run do_2()
until the next jiffy.

Instead, let's get the current jiffy, then wait until the next jiffy
to start our test.

Signed-off-by: Jim Kukunas <james.t.kukunas@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 5 insertions, 3 deletions

diff --git a/crypto/xor.c b/crypto/xor.c
index b75182d8ab14..87884435bddb 100644
--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -63,7 +63,7 @@ static void
 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
 {
         int speed;
-        unsigned long now;
+        unsigned long now, j;
         int i, count, max;
 
         tmpl->next = template_list;
@@ -76,9 +76,11 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
          */
         max = 0;
         for (i = 0; i < 5; i++) {
-                now = jiffies;
+                j = jiffies;
                 count = 0;
-                while (jiffies == now) {
+                while ((now = jiffies) == j)
+                        cpu_relax();
+                while (time_before(jiffies, now + 1)) {
                         mb(); /* prevent loop optimzation */
                         tmpl->do_2(BENCH_SIZE, b1, b2);
                         mb();