hujun260 opened a new pull request, #19687:
URL: https://github.com/apache/nuttx/pull/19687
## Summary
When a running task changes its CPU affinity on SMP and the new mask no
longer includes its current CPU, `nxsched_set_priority()` requests an
equal-priority reschedule on the current CPU. The task can be moved to
`g_readytorun` without waking the idle target CPU, leaving it unable to run
again.
Remove the task from its current CPU, add it back through
`nxsched_add_readytorun()` so a suitable CPU is selected, and switch context
unconditionally when the running task is no longer eligible for its current CPU.
Fixes #19680.
## Impact
- Existing SMP task-affinity behavior is corrected; no new feature or API is
added.
- No user adaptation is required.
- No impact on the build process, hardware interfaces, documentation,
security, or compatibility.
- Non-SMP scheduling behavior is unchanged.
## Testing
Build host: Ubuntu Linux, x86-64, GCC.
Target: QEMU ARM64, `qemu-armv8a:nsh_smp`, two Cortex-A53 CPUs.
Build command:
make distclean -j20
./tools/configure.sh -l qemu-armv8a:nsh_smp
make -j20
QEMU command:
qemu-system-aarch64 -cpu cortex-a53 -smp 2 -nographic \
-machine virt,virtualization=on,gic-version=3 -net none \
-chardev stdio,id=con,mux=on -serial chardev:con \
-mon chardev=con,mode=readline -kernel ./nuttx
A local reproducer starts two equal-priority `SCHED_RR` threads on CPU1. T0
changes its affinity to CPU0 while CPU0 is idle and T1 remains runnable on CPU1.
Before this change, T0 never resumes and the test stops after:
orphan: T0 started on CPU1
orphan: T1 started on CPU1
orphan: both tasks are ready; releasing T0
orphan: T0 changes affinity CPU1 -> CPU0
After this change, T0 resumes on CPU0:
orphan: T0 started on CPU1
orphan: T1 started on CPU1
orphan: both tasks are ready; releasing T0
orphan: T0 changes affinity CPU1 -> CPU0
orphan: sched_setaffinity ret=0, T0 resumed on CPU0
orphan: T0 resumed on CPU0 (affinity ret=0)
Code and commit checks:
./tools/checkpatch.sh -g HEAD~1..HEAD
✔️ All checks pass.
## PR verification Self-Check
- [x] This PR introduces only one functional change.
- [x] I have updated all required description fields above.
- [x] My PR adheres to the Contributing Guidelines and coding standard.
- [ ] My PR is still work in progress (not ready for review).
- [x] My PR is ready for review and can be safely merged into the codebase.
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