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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>
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>
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>
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>
