hrtimer: make the futex() system call use the per process slack value

This patch makes the futex() system call use the per process
slack value; with this users are able to externally control existing
applications to reduce the wakeup rate.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 4cd5b4319b04..8af10027514b 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1296,10 +1296,14 @@ static int futex_wait(u32 __user *uaddr, struct rw_semaphore *fshared,
                 if (!abs_time)
                         schedule();
                 else {
+                        unsigned long slack;
+                        slack = current->timer_slack_ns;
+                        if (rt_task(current))
+                                slack = 0;
                         hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC,
                                                 HRTIMER_MODE_ABS);
                         hrtimer_init_sleeper(&t, current);
-                        hrtimer_set_expires(&t.timer, *abs_time);
+                        hrtimer_set_expires_range_ns(&t.timer, *abs_time, slack);
 
                         hrtimer_start_expires(&t.timer, HRTIMER_MODE_ABS);
                         if (!hrtimer_active(&t.timer))