On 12/01/2023 12:00, Sebastian Andrzej Siewior wrote: > On 2022-12-19 16:15:00 [+0100], Krzysztof Kozlowski wrote: >> The PSCI cpuidle power domain in power_off callback uses >> __this_cpu_write() so it is PREEMPT_RT safe. This allows to use it in > > Why does __this_cpu_write() matter here? I'll reword to "not using sleeping primitives nor spinlock_t" > >> Realtime kernels and solves errors like: >> >> BUG: scheduling while atomic: swapper/2/0/0x00000002 >> Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT) >> Call trace: >> dump_backtrace.part.0+0xe0/0xf0 >> show_stack+0x18/0x40 >> dump_stack_lvl+0x68/0x84 >> dump_stack+0x18/0x34 >> __schedule_bug+0x60/0x80 >> __schedule+0x628/0x800 >> schedule_rtlock+0x28/0x5c >> rtlock_slowlock_locked+0x360/0xd30 >> rt_spin_lock+0x88/0xb0 >> genpd_lock_nested_spin+0x1c/0x30 >> genpd_power_off.part.0.isra.0+0x20c/0x2a0 >> genpd_runtime_suspend+0x150/0x2bc >> __rpm_callback+0x48/0x170 >> rpm_callback+0x6c/0x7c >> rpm_suspend+0x108/0x660 >> __pm_runtime_suspend+0x4c/0x8c >> __psci_enter_domain_idle_state.constprop.0+0x54/0xe0 >> psci_enter_domain_idle_state+0x18/0x2c >> cpuidle_enter_state+0x8c/0x4e0 >> cpuidle_enter+0x38/0x50 >> do_idle+0x248/0x2f0 >> cpu_startup_entry+0x24/0x30 >> secondary_start_kernel+0x130/0x154 >> __secondary_switched+0xb0/0xb4 > > This is to a sleeping lock (spinlock_t) in an IRQ-off region which > starts in do_idle(). You could describe the problem and to solution you > aim for instead pasting a backtrace into the commit description and > adding a flow in the code. I'll extend the description. > > I don't see how your commit description matches your change in code. One > might think "Oh. If I see this pattern, I need an irqsafe lock to fix > it". Best regards, Krzysztof
