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>

diff --git a/crypto/xor.c b/crypto/xor.c
index b75182d8ab1460b141619cc63af15d03fe6b2475..87884435bddb15b01abdc52cb801557452cc28f5 100644 (file)
--- 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();