From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kevin Hilman <khilman@kernel.org>, Ulf Hansson <ulf.hansson@linaro.org>, Daniel Lezcano <daniel.lezcano@linaro.org>, Lorenzo Pieralisi <lpieralisi@kernel.org>, Sudeep Holla <sudeep.holla@arm.com>, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Adrien Thierry <athierry@redhat.com>, Brian Masney <bmasney@redhat.com>, linux-rt-users@vger.kernel.org Subject: Re: [PATCH v2 2/5] cpuidle: psci: Mark as PREEMPT_RT safe Date: Thu, 12 Jan 2023 12:00:11 +0100 [thread overview] Message-ID: <Y7/oO8s26SKU8eOz@linutronix.de> (raw) In-Reply-To: <20221219151503.385816-3-krzysztof.kozlowski@linaro.org> 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? > 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 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". Sebastian _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kevin Hilman <khilman@kernel.org>, Ulf Hansson <ulf.hansson@linaro.org>, Daniel Lezcano <daniel.lezcano@linaro.org>, Lorenzo Pieralisi <lpieralisi@kernel.org>, Sudeep Holla <sudeep.holla@arm.com>, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Adrien Thierry <athierry@redhat.com>, Brian Masney <bmasney@redhat.com>, linux-rt-users@vger.kernel.org Subject: Re: [PATCH v2 2/5] cpuidle: psci: Mark as PREEMPT_RT safe Date: Thu, 12 Jan 2023 12:00:11 +0100 [thread overview] Message-ID: <Y7/oO8s26SKU8eOz@linutronix.de> (raw) In-Reply-To: <20221219151503.385816-3-krzysztof.kozlowski@linaro.org> 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? > 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 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". Sebastian
next prev parent reply other threads:[~2023-01-12 11:01 UTC|newest] Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-12-19 15:14 [PATCH v2 0/5] PM: Fixes for Realtime systems Krzysztof Kozlowski 2022-12-19 15:14 ` Krzysztof Kozlowski 2022-12-19 15:14 ` [PATCH v2 1/5] PM: domains: Add GENPD_FLAG_RT_SAFE for PREEMPT_RT Krzysztof Kozlowski 2022-12-19 15:14 ` Krzysztof Kozlowski 2023-01-04 15:45 ` Ulf Hansson 2023-01-04 15:45 ` Ulf Hansson 2023-01-06 14:52 ` Krzysztof Kozlowski 2023-01-06 14:52 ` Krzysztof Kozlowski 2023-01-12 10:36 ` Sebastian Andrzej Siewior 2023-01-12 10:36 ` Sebastian Andrzej Siewior 2023-01-12 11:27 ` Krzysztof Kozlowski 2023-01-12 11:27 ` Krzysztof Kozlowski 2023-01-12 10:32 ` Sebastian Andrzej Siewior 2023-01-12 10:32 ` Sebastian Andrzej Siewior 2023-01-12 11:31 ` Krzysztof Kozlowski 2023-01-12 11:31 ` Krzysztof Kozlowski 2022-12-19 15:15 ` [PATCH v2 2/5] cpuidle: psci: Mark as PREEMPT_RT safe Krzysztof Kozlowski 2022-12-19 15:15 ` Krzysztof Kozlowski 2023-01-12 11:00 ` Sebastian Andrzej Siewior [this message] 2023-01-12 11:00 ` Sebastian Andrzej Siewior 2023-01-12 11:32 ` Krzysztof Kozlowski 2023-01-12 11:32 ` Krzysztof Kozlowski 2023-01-17 15:27 ` Ulf Hansson 2023-01-17 15:27 ` Ulf Hansson 2023-01-19 15:40 ` Krzysztof Kozlowski 2023-01-19 15:40 ` Krzysztof Kozlowski 2023-01-19 17:06 ` Krzysztof Kozlowski 2023-01-19 17:06 ` Krzysztof Kozlowski 2022-12-19 15:15 ` [PATCH v2 3/5] cpuidle: psci: Do not suspend topology CPUs on PREEMPT_RT Krzysztof Kozlowski 2022-12-19 15:15 ` Krzysztof Kozlowski 2023-01-12 11:09 ` Sebastian Andrzej Siewior 2023-01-12 11:09 ` Sebastian Andrzej Siewior 2023-01-12 11:34 ` Krzysztof Kozlowski 2023-01-12 11:34 ` Krzysztof Kozlowski 2023-01-30 9:51 ` Sebastian Andrzej Siewior 2023-01-30 9:51 ` Sebastian Andrzej Siewior 2022-12-19 15:15 ` [PATCH v2 4/5] PM: Allow calling dev_pm_domain_set() with raw spinlock Krzysztof Kozlowski 2022-12-19 15:15 ` Krzysztof Kozlowski 2023-01-12 11:13 ` Sebastian Andrzej Siewior 2023-01-12 11:13 ` Sebastian Andrzej Siewior 2022-12-19 15:15 ` [PATCH v2 5/5] PM: domains: Do not call device_pm_check_callbacks() when holding genpd_lock() Krzysztof Kozlowski 2022-12-19 15:15 ` Krzysztof Kozlowski 2023-01-12 11:31 ` Sebastian Andrzej Siewior 2023-01-12 11:31 ` Sebastian Andrzej Siewior 2023-01-12 11:37 ` Krzysztof Kozlowski 2023-01-12 11:37 ` Krzysztof Kozlowski 2023-01-17 15:11 ` Ulf Hansson 2023-01-17 15:11 ` Ulf Hansson 2023-01-19 15:58 ` Krzysztof Kozlowski 2023-01-19 15:58 ` Krzysztof Kozlowski 2022-12-20 21:36 ` [PATCH v2 0/5] PM: Fixes for Realtime systems Adrien Thierry 2022-12-20 21:36 ` Adrien Thierry 2023-01-04 15:15 ` Ulf Hansson 2023-01-04 15:15 ` Ulf Hansson
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