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sched: Fix round-robin and watchdog re-arm under CONFIG_SCHED_TICKLESS. #20047

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sched: Fix round-robin and watchdog re-arm under CONFIG_SCHED_TICKLESS. #20047

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cdcd28e
sched/sched_addreadytorun: Arm round-robin timer on task switch-in.
FelipeMdeO Sep 2, 2026
008c603
sched/wdog: Clamp already-due watchdog re-arm to a minimum of one tick.
FelipeMdeO Sep 2, 2026
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11 changes: 11 additions & 0 deletions sched/sched/sched_addreadytorun.c
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,17 @@ bool nxsched_add_readytorun(FAR struct tcb_s *btcb)
btcb->flink->task_state = TSTATE_TASK_READYTORUN;
up_update_task(btcb);
ret = true;

#if defined(CONFIG_SCHED_TICKLESS) && CONFIG_RR_INTERVAL > 0
/* Tickless has no periodic tick to keep RR accounting alive, so
* arm the new task's timeslice timer explicitly on switch-in.
*/

if ((btcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_RR)
{
nxsched_reassess_timer();
}
#endif
}
else
{
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9 changes: 8 additions & 1 deletion sched/wdog/wdog.h
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Expand Up @@ -176,7 +176,14 @@ static inline_function void wd_timer_start(clock_t tick, bool in_expiration)
#ifdef CONFIG_SCHED_TICKLESS_ALARM
up_alarm_tick_start(next_tick);
#else
up_timer_tick_start(next_tick - clock_systime_ticks());
clock_t delta = next_tick - clock_systime_ticks();

/* Clamp to >= 1 tick: an already-expired 'delta' can go negative
* (overflows unsigned in arch code), and even zero can miss a
* oneshot timer's rising-edge match if the target is already due.
*/

up_timer_tick_start(delta > 0 ? delta : 1);
#endif
}

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