On 19/01/2023 16:40, Krzysztof Kozlowski wrote: > On 17/01/2023 16:27, Ulf Hansson wrote: >> On Mon, 19 Dec 2022 at 16:15, Krzysztof Kozlowski >> <krzysztof.kozlowski@xxxxxxxxxx> 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 >>> 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 >>> >>> Cc: Adrien Thierry <athierry@xxxxxxxxxx> >>> Cc: Brian Masney <bmasney@xxxxxxxxxx> >>> Cc: linux-rt-users@xxxxxxxxxxxxxxx >>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> >>> --- >>> drivers/cpuidle/cpuidle-psci-domain.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c >>> index c80cf9ddabd8..d15a91fb7048 100644 >>> --- a/drivers/cpuidle/cpuidle-psci-domain.c >>> +++ b/drivers/cpuidle/cpuidle-psci-domain.c >>> @@ -62,7 +62,8 @@ static int psci_pd_init(struct device_node *np, bool use_osi) >>> if (!pd_provider) >>> goto free_pd; >>> >>> - pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_CPU_DOMAIN; >>> + pd->flags |= GENPD_FLAG_IRQ_SAFE | GENPD_FLAG_RT_SAFE | \ >>> + GENPD_FLAG_CPU_DOMAIN; >> >> My main concern with this, is that it will affect the parent domains >> too. Whether those would be able to use the GENPD_FLAG_RT_SAFE or not, >> is a different story. >> >> In one way or the other, I think it would be better to limit the >> GENPD_FLAG_RT_SAFE to be used only for PREEMPT_RT kernels. > > I can do it... or maybe we should just drop the flags (RT and IRQ safe) > when parent domain does not have it? Actually, with next patch, I can skip this one entirely. This is needed if PSCI cpuidle driver invokes runtime PM functions which eventually puts PSCI cpuidle power domain into suspend/resume. If the former does not happen, the domain driver won't be even called so my problem disappears. Since I need patch 3/5 - effectively disabling PSCI cpuidle runtime PM - we can drop this one, till we find a real user needing it. Best regards, Krzysztof
