While booting i386 with Linux next 20200908 tag kernel this warning noticed.

metadata: git branch: master git repo: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git git commit: dff9f829e5b0181d4ed9d35aa62d695292399b54 git describe: next-20200908 kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/intel-core2-32/lkft/...

warning log: ----------------- [ 11.451223] Write protecting kernel text and read-only data: 20800k [ 11.457522] Run /sbin/init as init process [ 11.463807] random: fast init done [ 11.471527] [ 11.473118] ============================= [ 11.477129] WARNING: suspicious RCU usage [ 11.481135] 5.9.0-rc4-next-20200908 #1 Not tainted [ 11.485926] ----------------------------- [ 11.489931] /usr/src/kernel/include/trace/events/tlb.h:57 suspicious rcu_dereference_check() usage! [ 11.498970] [ 11.498970] other info that might help us debug this: [ 11.498970] [ 11.506961] [ 11.506961] rcu_scheduler_active = 2, debug_locks = 1 [ 11.513476] RCU used illegally from extended quiescent state! [ 11.519215] no locks held by swapper/0/0. [ 11.523217] [ 11.523217] stack backtrace: [ 11.527569] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200908 #1 [ 11.534955] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 11.542345] Call Trace: [ 11.544792] dump_stack+0x6d/0x8b [ 11.548112] lockdep_rcu_suspicious+0xb2/0xd0 [ 11.552473] switch_mm_irqs_off+0x508/0x510 [ 11.556658] switch_mm+0x19/0x50 [ 11.559890] leave_mm+0x2d/0x40 [ 11.563034] acpi_idle_enter_bm+0x1c/0x120 [ 11.567127] acpi_idle_enter+0x13b/0x230 [ 11.571049] ? rcu_eqs_enter.constprop.87+0x9e/0x180 [ 11.576008] ? acpi_idle_enter_s2idle+0x50/0x50 [ 11.580542] cpuidle_enter_state+0x87/0x560 [ 11.584732] cpuidle_enter+0x27/0x40 [ 11.588316] do_idle+0x20b/0x2a0 [ 11.591551] cpu_startup_entry+0x25/0x30 [ 11.595474] rest_init+0x166/0x230 [ 11.598881] arch_call_rest_init+0xd/0x19 [ 11.602893] start_kernel+0x481/0x4a0 [ 11.606562] i386_start_kernel+0x48/0x4a [ 11.610485] startup_32_smp+0x164/0x168 [ 11.614338] [ 11.614339] ============================= [ 11.614339] WARNING: suspicious RCU usage [ 11.614340] 5.9.0-rc4-next-20200908 #1 Not tainted [ 11.614340] ----------------------------- [ 11.614341] /usr/src/kernel/include/trace/events/lock.h:37 suspicious rcu_dereference_check() usage! [ 11.614341] [ 11.614341] other info that might help us debug this: [ 11.614342] [ 11.614342] [ 11.614342] rcu_scheduler_active = 2, debug_locks = 1 [ 11.614343] RCU used illegally from extended quiescent state! [ 11.614343] no locks held by swapper/0/0. [ 11.614343] [ 11.614344] stack backtrace: [ 11.614344] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200908 #1 [ 11.614345] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 11.614345] Call Trace: [ 11.614345] dump_stack+0x6d/0x8b [ 11.614346] lockdep_rcu_suspicious+0xb2/0xd0 [ 11.614346] lock_acquire+0x2d8/0x340 [ 11.614346] _raw_spin_lock+0x27/0x40 [ 11.614347] ? vprintk_emit+0x57/0x2c0 [ 11.614347] vprintk_emit+0x57/0x2c0 [ 11.614347] vprintk_default+0x17/0x20 [ 11.614348] vprintk_func+0x4f/0xd0 [ 11.614348] printk+0x13/0x15 [ 11.614348] lockdep_rcu_suspicious+0x21/0xd0 [ 11.614349] switch_mm_irqs_off+0x508/0x510 [ 11.614349] switch_mm+0x19/0x50 [ 11.614349] leave_mm+0x2d/0x40 [ 11.614350] acpi_idle_enter_bm+0x1c/0x120 [ 11.614350] acpi_idle_enter+0x13b/0x230 [ 11.614351] ? rcu_eqs_enter.constprop.87+0x9e/0x180 [ 11.614351] ? acpi_idle_enter_s2idle+0x50/0x50 [ 11.614351] cpuidle_enter_state+0x87/0x560 [ 11.614352] cpuidle_enter+0x27/0x40 [ 11.614352] do_idle+0x20b/0x2a0 [ 11.614352] cpu_startup_entry+0x25/0x30 [ 11.614353] rest_init+0x166/0x230 [ 11.614353] arch_call_rest_init+0xd/0x19 [ 11.614353] start_kernel+0x481/0x4a0 [ 11.614354] i386_start_kernel+0x48/0x4a [ 11.614354] startup_32_smp+0x164/0x168 [ 11.614354] [ 11.614355] ============================= [ 11.614355] WARNING: suspicious RCU usage [ 11.614356] 5.9.0-rc4-next-20200908 #1 Not tainted [ 11.614356] ----------------------------- [ 11.614356] /usr/src/kernel/include/trace/events/lock.h:63 suspicious rcu_dereference_check() usage! [ 11.614357] [ 11.614357] other info that might help us debug this: [ 11.614357] [ 11.614358] [ 11.614358] rcu_scheduler_active = 2, debug_locks = 1 [ 11.614358] RCU used illegally from extended quiescent state! [ 11.614359] 1 lock held by swapper/0/0: [ 11.614359] #0: c82fd670 (logbuf_lock){-...}-{2:2}, at: vprintk_emit+0x57/0x2c0 [ 11.614361] [ 11.614361] stack backtrace: [ 11.614362] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200908 #1 [ 11.614362] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 11.614362] Call Trace: [ 11.614363] dump_stack+0x6d/0x8b [ 11.614363] lockdep_rcu_suspicious+0xb2/0xd0 [ 11.614364] lock_release+0x23c/0x260 [ 11.614364] ? vprintk_emit+0x79/0x2c0 [ 11.614364] _raw_spin_unlock+0x16/0x30 [ 11.614365] vprintk_emit+0x79/0x2c0 [ 11.614365] vprintk_default+0x17/0x20 [ 11.614365] vprintk_func+0x4f/0xd0 [ 11.614366] printk+0x13/0x15 [ 11.614366] lockdep_rcu_suspicious+0x21/0xd0 [ 11.614366] switch_mm_irqs_off+0x508/0x510 [ 11.614367] switch_mm+0x19/0x50 [ 11.614367] leave_mm+0x2d/0x40 [ 11.614367] acpi_idle_enter_bm+0x1c/0x120 [ 11.614368] acpi_idle_enter+0x13b/0x230 [ 11.614368] ? rcu_eqs_enter.constprop.87+0x9e/0x180 [ 11.614368] ? acpi_idle_enter_s2idle+0x50/0x50 [ 11.614369] cpuidle_enter_state+0x87/0x560 [ 11.614369] cpuidle_enter+0x27/0x40 [ 11.614369] do_idle+0x20b/0x2a0 [ 11.614370] cpu_startup_entry+0x25/0x30 [ 11.614370] rest_init+0x166/0x230 [ 11.614370] arch_call_rest_init+0xd/0x19 [ 11.614371] start_kernel+0x481/0x4a0 [ 11.614371] i386_start_kernel+0x48/0x4a [ 11.614371] startup_32_smp+0x164/0x168

Full test log, https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20200908/tes...