dt(4): interval, profile: schedule clockintr relative to start of recording

For the interval and profile providers, schedule the first clock
interrupt to occur dp_nsecs nanoseconds after the start of recording.
This makes the interval between the start of recording and the first
event consistent across runs.

With input from claudio@.  Simplified by claudio@.

Thread: https://marc.info/?l=openbsd-tech&m=170879058205043&w=2

ok mpi@ claudio@

diff --git a/sys/dev/dt/dt_dev.c b/sys/dev/dt/dt_dev.c
index e111226..98b1979 100644 (file)
--- a/sys/dev/dt/dt_dev.c
+++ b/sys/dev/dt/dt_dev.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: dt_dev.c,v 1.31 2024/02/18 00:54:03 cheloha Exp $ */
+/*     $OpenBSD: dt_dev.c,v 1.32 2024/02/29 00:18:48 cheloha Exp $ */
 
 /*
  * Copyright (c) 2019 Martin Pieuchot <mpi@openbsd.org>
@@ -477,6 +477,7 @@ dt_ioctl_get_stats(struct dt_softc *sc, struct dtioc_stat *dtst)
 int
 dt_ioctl_record_start(struct dt_softc *sc)
 {
+       uint64_t now;
        struct dt_pcb *dp;
 
        if (sc->ds_recording)
@@ -487,6 +488,7 @@ dt_ioctl_record_start(struct dt_softc *sc)
                return ENOENT;
 
        rw_enter_write(&dt_lock);
+       now = nsecuptime();
        TAILQ_FOREACH(dp, &sc->ds_pcbs, dp_snext) {
                struct dt_probe *dtp = dp->dp_dtp;
 
@@ -497,7 +499,8 @@ dt_ioctl_record_start(struct dt_softc *sc)
                if (dp->dp_nsecs != 0) {
                        clockintr_bind(&dp->dp_clockintr, dp->dp_cpu, dt_clock,
                            dp);
-                       clockintr_advance(&dp->dp_clockintr, dp->dp_nsecs);
+                       clockintr_schedule(&dp->dp_clockintr,
+                           now + dp->dp_nsecs);
                }
        }
        rw_exit_write(&dt_lock);