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commit be9200f95a45eafc6877d24e8402f686f16bcca7 Author: ouyangxiangzhen <[email protected]> AuthorDate: Fri Sep 4 10:24:28 2026 +0800 sched/sched: Fix roundrobin scheduler timer if SCHED_TICKLESS enabled In tickless mode, the scheduler timer is stopped whenever the currently 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 task being switched in uses round-robin scheduling, so that the timer is always armed while an RR task is running. Hooking into nxsched_switch_context() covers all context switch paths (task context switch, interrupt exit, syscall and task exit) since every architecture calls it on every switch. Signed-off-by: ouyangxiangzhen <[email protected]> --- sched/sched/sched_switchcontext.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/sched/sched/sched_switchcontext.c b/sched/sched/sched_switchcontext.c index aa4c5e7e564..f2a708f5c4f 100644 --- a/sched/sched/sched_switchcontext.c +++ b/sched/sched/sched_switchcontext.c @@ -65,6 +65,15 @@ void nxsched_switch_context(FAR struct tcb_s *from, FAR struct tcb_s *to) } #endif +#if defined(CONFIG_SCHED_TICKLESS) && CONFIG_RR_INTERVAL > 0 + /* Before the context switch, we should set the timer for RR. */ + + if (from != to && (to->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_RR) + { + nxsched_reassess_timer(); + } +#endif + /* Indicate that the task has been suspended */ #ifdef CONFIG_SCHED_CRITMONITOR
