jerpelea opened a new pull request, #20259:
URL: https://github.com/apache/nuttx/pull/20259
## Summary
Fix three issues in the tickless scheduler / hrtimer path:
sched/hrtimer: Fix reprogram with wrong expiration when reinserting
hrtimer. In hrtimer_start_absolute(), when a pending hrtimer (previously the
head of the queue) is removed and reinserted with a later expiration, the
reprogram flag remains set although the timer is no longer the earliest one in
the queue. The old code passed hrtimer->expired to hrtimer_reprogram(); use
hrtimer_get_first()->expired instead so the hardware timer is always
reprogrammed with the actual earliest expiration.
sched/sched: Fix roundrobin if SCHED_TICKLESS enabled. In tickless mode
the scheduler timer is stopped whenever the running task requires no time
slicing (CLOCK_MAX). When a SCHED_RR task was later switched in, nothing
re-armed the timer, so the task could run indefinitely without round-robin
rotation. Reassess the scheduler timer in nxsched_switch_context() before the
context switch when the incoming task uses round-robin scheduling. Every
architecture invokes nxsched_switch_context() exactly once per context switch
(task switch, syscall, IRQ exit and task exit paths), so this covers all switch
paths.
sched/tickless: Fix SCHED_RR timeslice accounting on preemption. When an
RR task was preempted, its timeslice counter was not decremented for the time
already consumed, effectively granting the task bonus CPU time when resumed.
Perform RR accounting on context switches: nxsched_suspend_roundrobin() charges
the elapsed execution time against the timeslice of the RR task being switched
out, and nxsched_resume_roundrobin() re-arms the scheduler timer for the
remaining timeslice of the RR task being switched in, so the timer is always
armed while an RR task is running. This also removes the previous workaround in
nxsched_process_timer() that ran the scheduler logic on every timer tick.
## Impact
RELEASE
## Testing
CI
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