summaryrefslogtreecommitdiffstats
path: root/drivers/media/i2c/mt9v032.c
diff options
context:
space:
mode:
authorAlex Shi <alex.shi@linaro.org>2017-07-28 15:09:25 +0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-07-31 13:09:49 +0200
commit313c8c16ee62b32b8b40c6b00637b401dc19050e (patch)
tree392a1491c74d888594a793bcec95ea7f893167b5 /drivers/media/i2c/mt9v032.c
parent16f73eb02d7e1765ccab3d2018e0bd98eb93d973 (diff)
downloadblackbird-op-linux-313c8c16ee62b32b8b40c6b00637b401dc19050e.tar.gz
blackbird-op-linux-313c8c16ee62b32b8b40c6b00637b401dc19050e.zip
PM / CPU: replace raw_notifier with atomic_notifier
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>
Diffstat (limited to 'drivers/media/i2c/mt9v032.c')
0 files changed, 0 insertions, 0 deletions
OpenPOWER on IntegriCloud