I tested this series on top of tip/master and triggered the below warning when running the irqsoff tracer boot up test (config attached).
-- Steve Testing tracer irqsoff: ============================= WARNING: suspicious RCU usage 5.9.0-rc1-test+ #92 Not tainted ----------------------------- include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 RCU used illegally from extended quiescent state! no locks held by swapper/2/0. stack backtrace: CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.9.0-rc1-test+ #92 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 Call Trace: dump_stack+0x8d/0xc0 lock_acquire.cold+0x23/0x2c ? default_idle_call+0x4d/0x210 _raw_spin_lock_irqsave+0x50/0xa0 ? check_critical_timing+0x69/0x160 check_critical_timing+0x69/0x160 ? default_idle_call+0x4d/0x210 stop_critical_timings+0xdd/0xf0 default_idle_call+0x4d/0x210 do_idle+0x1f6/0x260 cpu_startup_entry+0x19/0x20 start_secondary+0x110/0x140 secondary_startup_64+0xb6/0xc0
