reacquire.go RawHistoryFolder

1package drm
2
3import "time"
4
5// masterRetry retries an enable modeset that the kernel refused because
6// DRM master was not back yet. The seat can report the session active
7// before the kernel hands master back; without a retry the output stays
8// dark until the next VT switch.
9//
10// The retry has a fixed deadline: the output loop wakes for many other
11// events (pings, cursor, reports) and must not push it back on each one.
12type masterRetry struct {
13	pending  bool
14	due      time.Time
15	attempts int
16}
17
18const (
19	masterRetryFirst = 20 * time.Millisecond
20	masterRetryMax   = time.Second
21	// masterRetryLimit bounds the retries of one enable (about 35 s).
22	masterRetryLimit = 40
23)
24
25// refused records an enable refused with err at now; only a lost master
26// is retried, and enabled stays false until a retry succeeds. It reports
27// that the retries are exhausted.
28func (m *masterRetry) refused(err error, enabled bool, now time.Time) (gaveUp bool) {
29	if !lostMaster(err) || enabled {
30		return false
31	}
32	if m.attempts >= masterRetryLimit {
33		m.pending = false
34		return true
35	}
36	m.pending = true
37	m.due = now.Add(min(masterRetryFirst<<min(m.attempts, 6), masterRetryMax))
38	return false
39}
40
41// fire starts an attempt: the retry is pending again only if it is refused.
42func (m *masterRetry) fire() {
43	m.pending = false
44	m.attempts++
45}
46
47// done ends the retry: the enable succeeded or the seat changed.
48func (m *masterRetry) done() { *m = masterRetry{} }
49
50// next is the time left before the next attempt, if one is due.
51func (m *masterRetry) next(now time.Time) (time.Duration, bool) {
52	if !m.pending {
53		return 0, false
54	}
55	return max(0, m.due.Sub(now)), true
56}