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
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next prev parent reply other threads:[~2023-01-12 11:01 UTC|newest]
Thread overview: 27+ 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 ` [PATCH v2 1/5] PM: domains: Add GENPD_FLAG_RT_SAFE for PREEMPT_RT Krzysztof Kozlowski
2023-01-04 15:45 ` Ulf Hansson
2023-01-06 14:52 ` Krzysztof Kozlowski
2023-01-12 10:36 ` Sebastian Andrzej Siewior
2023-01-12 11:27 ` Krzysztof Kozlowski
2023-01-12 10:32 ` Sebastian Andrzej Siewior
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
2023-01-12 11:00 ` Sebastian Andrzej Siewior [this message]
2023-01-12 11:32 ` Krzysztof Kozlowski
2023-01-17 15:27 ` Ulf Hansson
2023-01-19 15:40 ` 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
2023-01-12 11:09 ` Sebastian Andrzej Siewior
2023-01-12 11:34 ` Krzysztof Kozlowski
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
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
2023-01-12 11:31 ` Sebastian Andrzej Siewior
2023-01-12 11:37 ` Krzysztof Kozlowski
2023-01-17 15:11 ` Ulf Hansson
2023-01-19 15:58 ` Krzysztof Kozlowski
2022-12-20 21:36 ` [PATCH v2 0/5] PM: Fixes for Realtime systems Adrien Thierry
2023-01-04 15:15 ` Ulf Hansson
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