Node on a Raspberry Pi with worker threads does not use all isolated CPUs.

[mousseq]

Version

v22.21.0

Platform

Linux pi4-r-trixie 6.12.47+rpt-rpi-v8 #1 SMP PREEMPT Debian 1:6.12.47-1+rpt1 (2025-09-16) aarch64 GNU/Linux

Subsystem

Workers

What steps will reproduce the bug?

1. Create a node program that uses worker threads.
2. Isolate a set of CPUs by specifying isolcpus=... in /boot/firmware/cmdline.txt.
3. Reboot.
4. Execute htop in one window.
5. Execute the program on the isolated CPUs with taskset -c ... node node-program

How often does it reproduce? Is there a required condition?

Always occurs.

What is the expected behavior? Why is that the expected behavior?

The expected behavior is that the OS will distribute the node threads across all of the isolated CPUs.

What do you see instead?

The program and its threads all run on one of the isolated CPUs.

Additional information

I tried this on Bullseye and Bookworm too. Same behavior.