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2021-08-16PM: cpu: Make notifier chain use a raw_spinlock_tValentin Schneider1-12/+38
Invoking atomic_notifier_chain_notify() requires acquiring a spinlock_t, which can block under CONFIG_PREEMPT_RT. Notifications for members of the cpu_pm notification chain will be issued by the idle task, which can never block. Making *all* atomic_notifiers use a raw_spinlock is too big of a hammer, as only notifications issued by the idle task are problematic. Special-case cpu_pm_notifier_chain by kludging a raw_notifier and raw_spinlock_t together, matching the atomic_notifier behavior with a raw_spinlock_t. Fixes: 70d932985757 ("notifier: Fix broken error handling pattern") Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2020-09-01notifier: Fix broken error handling patternPeter Zijlstra1-30/+18
The current notifiers have the following error handling pattern all over the place: int err, nr; err = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr); if (err & NOTIFIER_STOP_MASK) __foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL) And aside from the endless repetition thereof, it is broken. Consider blocking notifiers; both calls take and drop the rwsem, this means that the notifier list can change in between the two calls, making @nr meaningless. Fix this by replacing all the __foo_notifier_call_chain() functions with foo_notifier_call_chain_robust() that embeds the above pattern, but ensures it is inside a single lock region. Note: I switched atomic_notifier_call_chain_robust() to use the spinlock, since RCU cannot provide the guarantee required for the recovery. Note: software_resume() error handling was broken afaict. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lore.kernel.org/r/20200818135804.325626653@infradead.org
2020-05-15kernel/cpu_pm: Fix uninitted local in cpu_pmDouglas Anderson1-2/+2
cpu_pm_notify() is basically a wrapper of notifier_call_chain(). notifier_call_chain() doesn't initialize *nr_calls to 0 before it starts incrementing it--presumably it's up to the callers to do this. Unfortunately the callers of cpu_pm_notify() don't init *nr_calls. This potentially means you could get too many or two few calls to CPU_PM_ENTER_FAILED or CPU_CLUSTER_PM_ENTER_FAILED depending on the luck of the stack. Let's fix this. Fixes: ab10023e0088 ("cpu_pm: Add cpu power management notifiers") Cc: stable@vger.kernel.org Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Stephen Boyd <swboyd@chromium.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20200504104917.v6.3.I2d44fc0053d019f239527a4e5829416714b7e299@changeid Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
2019-06-05treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282Thomas Gleixner1-10/+1
Based on 1 normalized pattern(s): this software is licensed under the terms of the gnu general public license version 2 as published by the free software foundation and may be copied distributed and modified under those terms this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 285 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190529141900.642774971@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-07-31PM / CPU: replace raw_notifier with atomic_notifierAlex Shi1-37/+13
This patch replaces an rwlock and raw notifier by an atomic notifier protected by a spin_lock and RCU. The main reason for this change is due to a 'scheduling while atomic' bug with RT kernels on ARM/ARM64. On ARM/ARM64, the rwlock cpu_pm_notifier_lock in cpu_pm_enter/exit() causes a potential schedule after IRQ disable in the idle call chain: cpu_startup_entry cpu_idle_loop local_irq_disable() cpuidle_idle_call call_cpuidle cpuidle_enter cpuidle_enter_state ->enter :arm_enter_idle_state cpu_pm_enter/exit CPU_PM_CPU_IDLE_ENTER read_lock(&cpu_pm_notifier_lock); <-- sleep in idle __rt_spin_lock(); schedule(); The kernel panic is here: [ 4.609601] BUG: scheduling while atomic: swapper/1/0/0x00000002 [ 4.609608] [<ffff0000086fae70>] arm_enter_idle_state+0x18/0x70 [ 4.609614] Modules linked in: [ 4.609615] [<ffff0000086f9298>] cpuidle_enter_state+0xf0/0x218 [ 4.609620] [<ffff0000086f93f8>] cpuidle_enter+0x18/0x20 [ 4.609626] Preemption disabled at: [ 4.609627] [<ffff0000080fa234>] call_cpuidle+0x24/0x40 [ 4.609635] [<ffff000008882fa4>] schedule_preempt_disabled+0x1c/0x28 [ 4.609639] [<ffff0000080fa49c>] cpu_startup_entry+0x154/0x1f8 [ 4.609645] [<ffff00000808e004>] secondary_start_kernel+0x15c/0x1a0 Daniel Lezcano said this notification is needed on arm/arm64 platforms. Sebastian suggested using atomic_notifier instead of rwlock, which is not only removing the sleeping in idle, but also improving latency. Tony Lindgren found a miss use that rcu_read_lock used after rcu_idle_enter Paul McKenney suggested trying RCU_NONIDLE. Signed-off-by: Alex Shi <alex.shi@linaro.org> Tested-by: Tony Lindgren <tony@atomide.com> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> [ rjw: Subject & changelog ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-09-03kernel/cpu_pm: fix cpu_cluster_pm_exit commentLina Iyer1-1/+1
cpu_cluster_pm_exit() must be sent after cpu_cluster_pm_enter() has been sent for the cluster and before any cpu_pm_exit() notifications are sent for any CPU. Cc: Nicolas Pitre <nicolas.pitre@linaro.org> Acked-by: Kevin Hilman <khilman@linaro.org> Signed-off-by: Lina Iyer <lina.iyer@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2012-05-31kernel/cpu_pm.c: fix various typosNicolas Pitre1-8/+8
Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Colin Cross <ccross@android.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-23cpu_pm: call notifiers during suspendColin Cross1-0/+33
Implements syscore_ops in cpu_pm to call the cpu and cpu cluster notifiers during suspend and resume, allowing drivers receiving the notifications to avoid implementing syscore_ops. Signed-off-by: Colin Cross <ccross@android.com> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Reviewed-by: Kevin Hilman <khilman@ti.com> Tested-and-Acked-by: Shawn Guo <shawn.guo@linaro.org> Tested-by: Vishwanath BS <vishwanath.bs@ti.com>
2011-09-23cpu_pm: Add cpu power management notifiersColin Cross1-0/+200
During some CPU power modes entered during idle, hotplug and suspend, peripherals located in the CPU power domain, such as the GIC, localtimers, and VFP, may be powered down. Add a notifier chain that allows drivers for those peripherals to be notified before and after they may be reset. Notified drivers can include VFP co-processor, interrupt controller and it's PM extensions, local CPU timers context save/restore which shouldn't be interrupted. Hence CPU PM event APIs must be called with interrupts disabled. Signed-off-by: Colin Cross <ccross@android.com> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Reviewed-by: Kevin Hilman <khilman@ti.com> Tested-and-Acked-by: Shawn Guo <shawn.guo@linaro.org> Tested-by: Kevin Hilman <khilman@ti.com> Tested-by: Vishwanath BS <vishwanath.bs@ti.com>