FYI, we noticed the following commit (built with gcc-4.9):
commit: f303fccb82928790ec58eea82722bd5c54d300b3 ("workqueue: implement "workqueue.debug_force_rr_cpu" debug feature")
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
in testcase: boot
on test machine: qemu-system-x86_64 -enable-kvm -cpu Nehalem -smp 2 -m 512M
caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
[ 0.890976] workqueue: round-robin CPU selection forced, expect performance impact
To reproduce:
git clone https://github.com/intel/lkp-tests.git
cd lkp-tests
bin/lkp qemu -k <bzImage> job-script # job-script is attached in this email
Thanks,
Xiaolong