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[client] scheduler: serialize cadence controls

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Keep one accepted frame-schedule control in flight until LGMP reports
that its serial has been consumed. Retain ambiguous tokens across pointer
queue recovery instead of retransmitting RESET or IMMEDIATE messages.

Back off acknowledgement polling and definite enqueue failures. Use modular
serial comparison so acknowledgement remains correct across rollover.
This commit is contained in:
Geoffrey McRae
2026-08-06 17:00:59 +10:00
parent fb1fb8447e
commit 1040683a3a
2 changed files with 79 additions and 15 deletions
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91
client/src/frame_scheduler.c
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@@ -35,6 +35,8 @@
#define FRAME_SCHEDULER_TARGET_SLACK_NS 500000ULL
#define FRAME_SCHEDULER_MIN_PERIOD_NS 2000000ULL
#define FRAME_SCHEDULER_MAX_PERIOD_NS 1000000000ULL
#define FRAME_SCHEDULER_CONTROL_RETRY_NS 10000000ULL
#define FRAME_SCHEDULER_CONTROL_RETRY_MAX 250000000ULL
static struct
{
@@ -43,10 +45,14 @@ static struct
_Atomic(bool) supported;
_Atomic(bool) active;
bool controlPending;
bool controlFaulted;
bool enqueueFaulted;
bool immediatePending;
_Atomic(uint32_t) generation;
_Atomic(uint64_t) period;
uint64_t lastSend;
uint64_t nextControlCheck;
uint64_t controlRetryDelay;
_Atomic(uint64_t) lastCadence;
int64_t phaseError;
@@ -70,24 +76,57 @@ static uint64_t presentationPeriod(void)
return 0;
}
static bool controlReady(void)
static void controlBackoff(uint64_t now)
{
uint64_t delay = l_frameScheduler.controlRetryDelay;
if (!delay)
delay = FRAME_SCHEDULER_CONTROL_RETRY_NS;
l_frameScheduler.nextControlCheck = now + delay;
l_frameScheduler.controlRetryDelay =
delay < FRAME_SCHEDULER_CONTROL_RETRY_MAX / 2 ?
delay * 2 : FRAME_SCHEDULER_CONTROL_RETRY_MAX;
}
static bool controlReady(uint64_t now)
{
if (!l_frameScheduler.controlPending)
return true;
return now >= l_frameScheduler.nextControlCheck;
if (now < l_frameScheduler.nextControlCheck)
return false;
const LG_TransportStatus status = g_state.transportOps->controlStatus(
g_state.transport, l_frameScheduler.controlToken);
if (status == LG_TRANSPORT_UNAVAILABLE)
if (status != LG_TRANSPORT_OK)
{
if (status != LG_TRANSPORT_UNAVAILABLE &&
!l_frameScheduler.controlFaulted)
{
DEBUG_WARN(
"Frame-schedule acknowledgement failed with status %d", status);
l_frameScheduler.controlFaulted = true;
}
controlBackoff(now);
return false;
}
l_frameScheduler.controlPending = false;
return status == LG_TRANSPORT_OK;
l_frameScheduler.controlPending = false;
l_frameScheduler.nextControlCheck = 0;
l_frameScheduler.controlRetryDelay =
FRAME_SCHEDULER_CONTROL_RETRY_NS;
if (l_frameScheduler.controlFaulted)
{
l_frameScheduler.controlFaulted = false;
l_frameScheduler.immediatePending = true;
}
return true;
}
static bool sendSchedule(LG_TransportFrameScheduleFlags flags,
uint64_t period)
uint64_t period, uint64_t now)
{
if (!controlReady())
if (!controlReady(now))
return false;
int64_t phaseError;
@@ -118,15 +157,24 @@ static bool sendSchedule(LG_TransportFrameScheduleFlags flags,
const LG_TransportStatus status = g_state.transportOps->sendControl(
g_state.transport, &control, &l_frameScheduler.controlToken);
if (status == LG_TRANSPORT_UNAVAILABLE)
return false;
if (status != LG_TRANSPORT_OK)
{
DEBUG_WARN("Frame-schedule control failed with status %d", status);
if (status != LG_TRANSPORT_UNAVAILABLE &&
!l_frameScheduler.enqueueFaulted)
{
DEBUG_WARN("Frame-schedule control failed with status %d", status);
l_frameScheduler.enqueueFaulted = true;
}
controlBackoff(now);
return false;
}
l_frameScheduler.controlPending = true;
l_frameScheduler.controlPending = true;
l_frameScheduler.enqueueFaulted = false;
l_frameScheduler.nextControlCheck =
now + FRAME_SCHEDULER_CONTROL_RETRY_NS;
l_frameScheduler.controlRetryDelay =
FRAME_SCHEDULER_CONTROL_RETRY_NS;
if (flags & LG_TRANSPORT_FRAME_SCHEDULE_IMMEDIATE)
l_frameScheduler.immediatePending = false;
LG_LOCK(l_frameScheduler.lock);
@@ -155,8 +203,13 @@ void frameScheduler_start(LG_TransportFeatureFlags features)
features & LG_TRANSPORT_FEATURE_FRAME_SCHEDULE;
l_frameScheduler.active = false;
l_frameScheduler.controlPending = false;
l_frameScheduler.controlFaulted = false;
l_frameScheduler.enqueueFaulted = false;
l_frameScheduler.immediatePending = true;
l_frameScheduler.lastSend = 0;
l_frameScheduler.nextControlCheck = 0;
l_frameScheduler.controlRetryDelay =
FRAME_SCHEDULER_CONTROL_RETRY_NS;
l_frameScheduler.lastCadence = 0;
++l_frameScheduler.generation;
@@ -173,12 +226,21 @@ void frameScheduler_start(LG_TransportFeatureFlags features)
void frameScheduler_stop(void)
{
if (l_frameScheduler.supported && l_frameScheduler.active)
sendSchedule(LG_TRANSPORT_FRAME_SCHEDULE_RELEASE, 0);
{
// Poll an accepted message once more before abandoning it with the
// session. A definite enqueue failure is safe to retry immediately.
l_frameScheduler.nextControlCheck = 0;
sendSchedule(
LG_TRANSPORT_FRAME_SCHEDULE_RELEASE, 0, nanotime());
}
l_frameScheduler.supported = false;
l_frameScheduler.active = false;
l_frameScheduler.controlPending = false;
l_frameScheduler.controlFaulted = false;
l_frameScheduler.enqueueFaulted = false;
l_frameScheduler.immediatePending = false;
l_frameScheduler.nextControlCheck = 0;
}
void frameScheduler_observeCadence(void)
@@ -199,7 +261,8 @@ void frameScheduler_update(void)
now - lastCadence > FRAME_SCHEDULER_CADENCE_GRACE_NS)
{
if (l_frameScheduler.active &&
sendSchedule(LG_TRANSPORT_FRAME_SCHEDULE_RELEASE, 0))
sendSchedule(
LG_TRANSPORT_FRAME_SCHEDULE_RELEASE, 0, now))
{
l_frameScheduler.active = false;
l_frameScheduler.period = 0;
@@ -266,7 +329,7 @@ void frameScheduler_update(void)
if (l_frameScheduler.immediatePending)
flags |= LG_TRANSPORT_FRAME_SCHEDULE_IMMEDIATE;
if (sendSchedule(flags, l_frameScheduler.period))
if (sendSchedule(flags, l_frameScheduler.period, now))
{
l_frameScheduler.active = true;
l_frameScheduler.lastSend = now;