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Skip task/timer updated if late for more than a few periods #129

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merged 1 commit into from
Jan 28, 2016
Merged

Skip task/timer updated if late for more than a few periods #129

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8 changes: 7 additions & 1 deletion rtt/os/Timer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,8 @@ namespace RTT {

// Wait
int ret = 0;
if ( wake_up_time > rtos_get_time_ns() )
Time now = rtos_get_time_ns();
if ( wake_up_time > now )
ret = msem.waitUntil( wake_up_time ); // case of no timers or running timers
else
ret = -1; // case of timer overrun.
Expand All @@ -99,6 +100,11 @@ namespace RTT {
TimerIds::iterator tim = mtimers.begin() + next_timer_id;
if ( tim->period ) {
// periodic timer
// if late by more than 4 periods, skip late updates
int maxDelayInPeriods = 4;
if (now - tim->expires > tim->period*maxDelayInPeriods) {
tim->expires += tim->period*((now - tim->expires) / tim->period);
}
tim->expires += tim->period;
} else {
// aperiodic timer
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9 changes: 8 additions & 1 deletion rtt/os/gnulinux/fosi_internal.cpp
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Expand Up @@ -254,9 +254,16 @@ namespace RTT

if (task->wait_policy == ORO_WAIT_ABS)
{
// in the case of overrun by more than 4 periods,
// skip all the updates before now, with the next update aligned to period
int maxDelayInPeriods = 4;
NANO_TIME period = task->period;
if (now - wake > maxDelayInPeriods*period) {
period = period * ((now - wake) / period);
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Actually this should have been

period += period * ((now - wake) / period);

because we always want to add at least one period (line 260) plus eventually the additional ones, like in Timer.cpp:108.

}
// program next period:
// 1. convert period to timespec
TIME_SPEC ts = ticks2timespec( nano2ticks( task->period) );
TIME_SPEC ts = ticks2timespec( nano2ticks(period) );
// 2. Add ts to periodMark (danger: tn guards for overflows!)
NANO_TIME tn = (task->periodMark.tv_nsec + ts.tv_nsec);
task->periodMark.tv_nsec = tn % 1000000000LL;
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