FYI, we noticed the following commit: commit: acb04058de49458010c44bb35b849d45113fd668 ("sched/clock: Fix hotplug crash") https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master in testcase: cpu-hotplug with following parameters: on test machine: qemu-system-x86_64 -enable-kvm -cpu Nehalem -smp 2 -m 1G caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace): +-------------------------------------+------------+------------+ | | 02cfdc95a0 | acb04058de | +-------------------------------------+------------+------------+ | boot_successes | 4 | 0 | | boot_failures | 0 | 4 | | INFO:suspicious_RCU_usage | 0 | 4 | | RCU_used_illegally_from_offline_CPU | 0 | 4 | +-------------------------------------+------------+------------+ [ 30.328035] masked ExtINT on CPU#1 [ 30.328035] [ 30.328035] =============================== [ 30.328035] [ INFO: suspicious RCU usage. ] [ 30.328035] 4.10.0-rc3-00271-gacb0405 #1 Not tainted [ 30.328035] ------------------------------- [ 30.328035] kernel/workqueue.c:712 sched RCU or wq_pool_mutex should be held! [ 30.328035] [ 30.328035] other info that might help us debug this: [ 30.328035] [ 30.328035] [ 30.328035] RCU used illegally from offline CPU! [ 30.328035] rcu_scheduler_active = 1, debug_locks = 0 [ 30.328035] no locks held by swapper/1/0. [ 30.328035] [ 30.328035] stack backtrace: [ 30.328035] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.10.0-rc3-00271-gacb0405 #1 [ 30.328035] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014 [ 30.328035] Call Trace: [ 30.328035] dump_stack+0x86/0xc0 [ 30.328035] lockdep_rcu_suspicious+0xf7/0x100 [ 30.328035] get_work_pool+0x55/0xa6 To reproduce: git clone git://git.kernel.org/pub/scm/linux/kernel/git/wfg/lkp-tests.git cd lkp-tests bin/lkp qemu -k job-script # job-script is attached in this email Thanks, Xiaolong