Improve ability to reschedule phased loops in AOS
This makes it so that users can reliably reschedule phased loops in a
well-defined way, for situations, e.g., where there may be a need to
update the offset of the loop dynamically.
This slightly changes the default semantics around dynamically changing
the interval/offset of a phased loop, but I don't actually see anyone
doing that currently, and there were some poorly-defined corner cases
anyways.
References: PRO-18058
Change-Id: I679c905da1582d250deb7f9607c8517ed34e5a25
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/util/phased_loop.cc b/aos/util/phased_loop.cc
index 53f6f4d..1f61775 100644
--- a/aos/util/phased_loop.cc
+++ b/aos/util/phased_loop.cc
@@ -17,15 +17,26 @@
void PhasedLoop::set_interval_and_offset(
const monotonic_clock::duration interval,
- const monotonic_clock::duration offset) {
+ const monotonic_clock::duration offset,
+ std::optional<monotonic_clock::time_point> monotonic_now) {
// Update last_time_ to the new offset so that we have an even interval
- last_time_ += offset - offset_;
+ // In doing so, set things so that last_time_ will only ever decrease on calls
+ // to set_interval_and_offset.
+ last_time_ += offset - offset_ -
+ (offset > offset_ ? interval : monotonic_clock::duration(0));
interval_ = interval;
offset_ = offset;
CHECK(offset_ >= monotonic_clock::duration(0));
CHECK(interval_ > monotonic_clock::duration(0));
CHECK(offset_ < interval_);
+ // Reset effectively clears the skipped iteration count and ensures that the
+ // last time is in the interval (monotonic_now - interval, monotonic_now],
+ // which means that a call to Iterate(monotonic_now) will return 1 and set a
+ // wakeup time after monotonic_now.
+ if (monotonic_now.has_value()) {
+ Iterate(monotonic_now.value());
+ }
}
monotonic_clock::duration PhasedLoop::OffsetFromIntervalAndTime(