LITMUS^RT core: hook into hrtimer_nanosleep()

To intercept absolute-timed nanosleeps relative to CLOCK_MONOTONIC,
which are likely related to periodic job arrivals.

1 files changed, 16 insertions, 0 deletions

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index a6d5b061ee67..0cc8ab474d4a 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1622,6 +1622,19 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
         if (dl_task(current) || rt_task(current) || is_realtime(current))
                 slack = 0;
 
+        if (is_realtime(current)
+                && clockid == CLOCK_MONOTONIC
+                && mode == HRTIMER_MODE_ABS) {
+                /* special handling: to handle periodic activations
+                 * correctly despite timer interrupt jitter and overheads,
+                 * the plugin might need to know the time at which the
+                 * task intends to wake up
+                 */
+                tsk_rt(current)->doing_abs_nanosleep = 1;
+                tsk_rt(current)->nanosleep_wakeup =
+                        ktime_to_ns(timespec_to_ktime(*rqtp));
+        }
+
         hrtimer_init_on_stack(&t.timer, clockid, mode);
         hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
         if (do_nanosleep(&t, mode))
@@ -1648,6 +1661,9 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
         ret = -ERESTART_RESTARTBLOCK;
 out:
         destroy_hrtimer_on_stack(&t.timer);
+
+        tsk_rt(current)->doing_abs_nanosleep = 0;
+
         return ret;
 }