On arm64 qemu_arm64, juno-r2 and dragonboard-410c while running kselftest ftrace on stable rc 5.5.1-rc1 to till today 5.5.16-rc2 and 5.6 found this kernel warning.
[ 386.349099] kselftest: Running tests in ftrace [ 393.984018] [ 393.984290] ============================= [ 393.984781] WARNING: suspicious RCU usage [ 393.988690] 5.6.3-rc2 #1 Not tainted [ 393.992679] ----------------------------- [ 393.996327] /usr/src/kernel/include/trace/events/ipi.h:36 suspicious rcu_dereference_check() usage! [ 394.000241] [ 394.000241] other info that might help us debug this: [ 394.000241] [ 394.009094] [ 394.009094] RCU used illegally from idle CPU! [ 394.009094] rcu_scheduler_active = 2, debug_locks = 1 [ 394.017084] RCU used illegally from extended quiescent state! [ 394.028187] 1 lock held by swapper/3/0: [ 394.033826] #0: ffff80001237b6a8 (max_trace_lock){....}, at: check_critical_timing+0x7c/0x1a8 [ 394.037480] [ 394.037480] stack backtrace: [ 394.046158] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.6.3-rc2 #1 [ 394.050584] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT) [ 394.056663] Call trace: [ 394.063515] dump_backtrace+0x0/0x1e0 [ 394.065686] show_stack+0x24/0x30 [ 394.069505] dump_stack+0xe8/0x150 [ 394.072805] lockdep_rcu_suspicious+0xcc/0x110 [ 394.076106] arch_irq_work_raise+0x208/0x210 [ 394.080533] __irq_work_queue_local+0x5c/0x80 [ 394.084959] irq_work_queue+0x38/0x78 [ 394.089212] __update_max_tr+0x150/0x218 [ 394.092858] update_max_tr_single.part.82+0x98/0x100 [ 394.096851] update_max_tr_single+0x1c/0x28 [ 394.101798] check_critical_timing+0x198/0x1a8 [ 394.105705] stop_critical_timings+0x128/0x148 [ 394.110221] cpuidle_enter_state+0x74/0x4f8 [ 394.114645] cpuidle_enter+0x3c/0x50 [ 394.118726] call_cpuidle+0x44/0x80 [ 394.122542] do_idle+0x22c/0x2d0 [ 394.125755] cpu_startup_entry+0x28/0x48 [ 394.129229] secondary_start_kernel+0x1b4/0x210
metadata: git branch: linux-5.5.y and linux-5.6.y git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git kernel-config: http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/juno/lkft/linux-stab...
Full test log, 5.6 test logs, https://lkft.validation.linaro.org/scheduler/job/1350627#L12612 https://lkft.validation.linaro.org/scheduler/job/1350731#L9509
5.5 test logs, https://lkft.validation.linaro.org/scheduler/job/1322704#L9777 https://lkft.validation.linaro.org/scheduler/job/1153369#L9745 https://lkft.validation.linaro.org/scheduler/job/1351155#L8982 https://lkft.validation.linaro.org/scheduler/job/1351065#L12349
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