evolution124 opened a new issue, #19680:
URL: https://github.com/apache/nuttx/issues/19680
### Description / Steps to reproduce the issue
on latest nuttx, configure with nsh64 & smp & and CONFIG_SMP_NCPU is 2.
The issue is after adjust task's affinity, the task may became an orphan
task which will never be scheduled to run any more.
### 1. The setup are like bellow:
1.1) M is main task
1.2) T0, T1 are task0 and task1
2.3) C0, C1 are CPU0 and CPU1
### 2. The issue produced as bellow.
2.1) main task create two task, t0 and t1.
**M task**
**-> pthread_create(t0, t0_task_entry ....)**
**-> pthread_create(t1, t1_task_entry ....)**
2.2) sometimes, t0 and t1 may scheduled to CPU1
**t0 running on CPU1**
**-> t0 set affinity to CPU0 (by sched_setaffinity)**
**t1 is pending on CPU1 because t0 is running.**
2.3) schedule tick came, t0 goto g_readytorun
**t0 switching out to g_readytorun tasklist(the affinity is CPU0,
not CPU1, so in SMP goto g_readylist)**
**t1 switching in, set t1's affinity to CPU1 (by sched_setaffinity)**
2.4) because prevsiously all the tasks are created on CPU1, so CPU0 only
have idle task, which do not have TCB_FLAG_SCHED_RR flag, then t0 in
g_readytorun task list became an orphan task(no schedule running). Code as
bellow.
```
//./nuttxspace/nuttx/sched/sched/sched_processtick.c
static inline void nxsched_cpu_scheduler(int cpu)
{
FAR struct tcb_s *rtcb = current_task(cpu);
...
//idle task won't branch to run nxsched_process_roundrobin(...)
if ((rtcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_RR)
{
//this will not be called because the rtcb is idle task which does
not have TCB_FLAG_SCHED_RR flag.
**nxsched_process_roundrobin(rtcb, 1, false);
}
```
### On which OS does this issue occur?
[OS: Linux]
### What is the version of your OS?
Ubuntu 22.04.4 LTS
### NuttX Version
375462322eeb6d2da57e6dff84c747a56bfa2eef (origin/master)
### Issue Architecture
[Arch: risc-v]
### Issue Area
[Area: OS Components], [Area: Kernel]
### Host information
qemu to run the rv64
qemu-system-riscv64 --version
QEMU emulator version 10.0.0
Copyright (c) 2003-2025 Fabrice Bellard and the QEMU Project developers
### Verification
- [x] I have verified before submitting the report.
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