While booting arm64 hikey board with stable-rc 5.9.13-rc1 the following warning noticed. This is hard to reproduce. Step to reproduce: ------------------------ # Boot arm64 hikey device with stable-rc 5.9.13-rc1 # Since it is hard to reproduce you may notice this warning Crash log : -------------- [ 10.763081] [drm] Initialized kirin 1.0.0 20150718 for f4100000.ade on minor 1 [ 10.764088] Bluetooth: hci0: change remote baud rate command in firmware [[0;32m OK [0m] Started TEE Supplicant. [ 10.791741] mmc_host mmc2: Bus speed (slot 0) = 24800000Hz (slot req 400000Hz, actual 400000HZ div = 31) E/TC:0 tee_entry_std:545 Bad arg address 0x6b681000 [[0;32m OK [0m] Started Periodic Command Scheduler. [ 10.846417] mmc_host mmc2: Bus speed (slot 0) = 24800000Hz (slot req 25000000Hz, actual 24800000HZ div = 0) [ 10.887083] [ 10.887087] [ 10.887095] ===================================== [ 10.887098] ============================= [ 10.887101] WARNING: bad unlock balance detected! [ 10.887107] WARNING: suspicious RCU usage [ 10.887112] 5.9.13-rc1 #1 Not tainted [ 10.887120] 5.9.13-rc1 #1 Not tainted [ 10.887122] ------------------------------------- [ 10.887129] systemd-udevd/306 is trying to release lock ( [ 10.887133] ----------------------------- [ 10.887135] fs_reclaim) at: [ 10.887144] /usr/src/kernel/kernel/sched/core.c:7270 Illegal context switch in RCU-bh read-side critical section! [ 10.887163] [<ffff80001030f2e8>] __alloc_pages_nodemask+0x250/0x4c0 [ 10.887166] [ 10.887166] other info that might help us debug this: [ 10.887166] [ 10.887170] but there are no more locks to release! [ 10.887175] [ 10.887175] other info that might help us debug this: [ 10.887179] [ 10.887179] rcu_scheduler_active = 2, debug_locks = 0 [ 10.887182] 1 lock held by systemd-udevd/306: [ 10.887189] 1 lock held by systemd-sysctl/342: [ 10.887192] #0: ffff00007474e518 [ 10.887199] #0: [ 10.887202] ( [ 10.887209] ffff000070c54708 [ 10.887212] &mm->mmap_lock){++++}-{3:3} [ 10.887219] ( [ 10.887228] , at: do_page_fault+0x168/0x420 [ 10.887230] &type->i_mutex_dir_key [ 10.887235] [ 10.887235] stack backtrace: [ 10.887237] #3){++++}-{3:3} [ 10.887246] CPU: 1 PID: 306 Comm: systemd-udevd Not tainted 5.9.13-rc1 #1 [ 10.887255] , at: iterate_dir+0x54/0x1d0 [ 10.887258] Hardware name: HiKey Development Board (DT) [ 10.887264] [ 10.887264] stack backtrace: [ 10.887266] Call trace: [ 10.887276] dump_backtrace+0x0/0x1f8 [ 10.887283] show_stack+0x2c/0x38 [ 10.887292] dump_stack+0xec/0x158 [ 10.887303] print_unlock_imbalance_bug+0xec/0xf0 [ 10.887311] lock_release+0x300/0x388 [ 10.887320] __alloc_pages_nodemask+0x268/0x4c0 [ 10.887329] alloc_pages_vma+0x90/0x240 [ 10.887338] handle_mm_fault+0x8d4/0x12f0 [ 10.887346] do_page_fault+0x1c4/0x420 [ 10.887353] do_translation_fault+0xb0/0xcc [ 10.887363] do_mem_abort+0x50/0xb0 [ 10.887372] el1_abort+0x28/0x30 [ 10.887379] el1_sync_handler+0xc0/0xf0 [ 10.887386] el1_sync+0x7c/0x100 [ 10.887397] __arch_copy_to_user+0x1d8/0x310 [ 10.887407] copy_page_to_iter+0x110/0x3e8 [ 10.887416] generic_file_buffered_read+0x4b8/0xaa8 [ 10.887423] generic_file_read_iter+0xd4/0x168 [ 10.887432] blkdev_read_iter+0x50/0x78 [ 10.887442] new_sync_read+0x100/0x1a0 [ 10.887449] vfs_read+0x1b4/0x1d8 [ 10.887457] ksys_read+0x74/0xf8 [ 10.887465] __arm64_sys_read+0x24/0x30 [ 10.887472] el0_svc_common.constprop.3+0x7c/0x198 [ 10.887478] do_el0_svc+0x34/0xa0 [ 10.887486] el0_sync_handler+0x16c/0x210 [ 10.887492] el0_sync+0x140/0x180 [ 10.887504] CPU: 6 PID: 342 Comm: systemd-sysctl Not tainted 5.9.13-rc1 #1 [ 10.887510] Hardware name: HiKey Development Board (DT) [ 10.887515] Call trace: [ 10.887524] dump_backtrace+0x0/0x1f8 [ 10.887531] show_stack+0x2c/0x38 [ 10.887542] dump_stack+0xec/0x158 [ 10.887552] lockdep_rcu_suspicious+0xd4/0xf8 [ 10.887561] ___might_sleep+0x1e4/0x208 [ 10.887569] __might_sleep+0x54/0x90 [ 10.887577] __might_fault+0x58/0xa8 [ 10.887584] filldir64+0x1f0/0x488 [ 10.887593] call_filldir+0xb0/0x140 [ 10.887600] ext4_readdir+0x700/0x900 [ 10.887607] iterate_dir+0x88/0x1d0 [ 10.887615] __arm64_sys_getdents64+0x70/0x1a0 [ 10.887622] el0_svc_common.constprop.3+0x7c/0x198 [ 10.887629] do_el0_svc+0x34/0xa0 [ 10.887637] el0_sync_handler+0x16c/0x210 [ 10.887644] el0_sync+0x140/0x180 [ 10.912334] Console: switching to colour frame buffer device 256x72 Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> Full boot log link, https://qa-reports.linaro.org/lkft/linux-stable-rc-linux-5.9.y/build/v5.9.12-47-g1372e1af58d4/testrun/3538040/suite/linux-log-parser/test/check-kernel-warning-2012813/log metadata: git branch: linux-5.9.y git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git git commit: 1372e1af58d410676db7917cc3484ca22d471623 git describe: v5.9.12-47-g1372e1af58d4 make_kernelversion: 5.9.13-rc1 kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/hikey/lkft/linux-stable-rc-5.9/47/config -- Linaro LKFT https://lkft.linaro.org