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Fixed

LIN1021-806 : Extra interrupts counted on isolated cores - only on ARM

Created: Jul 13, 2021 Updated: Aug 25, 2021

Resolved Date: Jul 26, 2021

Found In Version: 10.21.20.1

Fix Version: 10.21.20.3

Severity: Standard

Applicable for: Wind River Linux LTS 21

Component/s: Kernel

Description

an increasing count on interrupts on cores that are isolated -
the isolated cores are getting local ticks, even when idle.

Steps to Reproduce

BSPs: intel-socfpga64 or marvell-cn96xx

boot cmdline for cpu isol: <...> rootwait rw maxcpus=6 coherent_pool=16M fsck.mode=force fsck.repair=yes arm_smmu_v3.disable_bypass=0 iommu.passthrough=1 oops=panic console=ttyAMA0,115200n8 earlycon=pl011,0x87e028000000 earlyprintk isolcpus=1-5 nohz_full=1-5 rcu_nocbs=1-5 systemd.log_level=6 loglevel=4

To check interrupt count:

cat /proc/interrupts

To reproduce: run a tight loop and check interrupt count on isolated cores