pktgen: remove ndelay() call

Daniel Turull reported inaccuracies in pktgen when using low packet
rates, because we call ndelay(val) with values bigger than 20000.

Instead of calling ndelay() for delays < 100us, we can instead loop
calling ktime_now() only.

Reported-by: Daniel Turull <daniel.turull@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 4 deletions

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 6bbf00801f61..0001c243b35c 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2145,9 +2145,12 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until)
         }
 
         start_time = ktime_now();
-        if (remaining < 100000)
-                ndelay(remaining);      /* really small just spin */
-        else {
+        if (remaining < 100000) {
+                /* for small delays (<100us), just loop until limit is reached */
+                do {
+                        end_time = ktime_now();
+                } while (ktime_lt(end_time, spin_until));
+        } else {
                 /* see do_nanosleep */
                 hrtimer_init_sleeper(&t, current);
                 do {
@@ -2162,8 +2165,8 @@ static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until)
                         hrtimer_cancel(&t.timer);
                 } while (t.task && pkt_dev->running && !signal_pending(current));
                 __set_current_state(TASK_RUNNING);
+                end_time = ktime_now();
         }
-        end_time = ktime_now();
 
         pkt_dev->idle_acc += ktime_to_ns(ktime_sub(end_time, start_time));
         pkt_dev->next_tx = ktime_add_ns(spin_until, pkt_dev->delay);