* [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock
@ 2017-06-14 13:22 Alex Shi
2017-06-16 3:12 ` Alex Shi
2017-06-16 15:40 ` Sebastian Andrzej Siewior
0 siblings, 2 replies; 3+ messages in thread
From: Alex Shi @ 2017-06-14 13:22 UTC (permalink / raw)
To: open list
Cc: Alex Shi, Sebastian Andrzej Siewior, Thomas Gleixner,
Anders Roxell, Daniel Lezcano, linux-rt-users
This is a quick fix for a bug as 'scheduling while atomic' or
'scheduling from the idle thread' on arm/arm64.
On arm/arm64, rwlock cpu_pm_notifier_lock in cpu_pm cause a potential
schedule after irq disable in 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.
I also tried use local_lock_irq to replace local_irq_disable, but my 2
boards just die without any output. So maybe it's only quick way to
make rt kernel work on arm/arm64.
Since this is quick fix, instead of split out the raw rwlock, to use
raw_spin_lock is simple and don't cost much.
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
---
kernel/cpu_pm.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
index 009cc9a..8ffa13e3 100644
--- a/kernel/cpu_pm.c
+++ b/kernel/cpu_pm.c
@@ -22,7 +22,7 @@
#include <linux/spinlock.h>
#include <linux/syscore_ops.h>
-static DEFINE_RWLOCK(cpu_pm_notifier_lock);
+static DEFINE_RAW_SPINLOCK(cpu_pm_notifier_lock);
static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
@@ -50,9 +50,9 @@ int cpu_pm_register_notifier(struct notifier_block *nb)
unsigned long flags;
int ret;
- write_lock_irqsave(&cpu_pm_notifier_lock, flags);
+ raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
ret = raw_notifier_chain_register(&cpu_pm_notifier_chain, nb);
- write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
+ raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
return ret;
}
@@ -72,9 +72,9 @@ int cpu_pm_unregister_notifier(struct notifier_block *nb)
unsigned long flags;
int ret;
- write_lock_irqsave(&cpu_pm_notifier_lock, flags);
+ raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
ret = raw_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
- write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
+ raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
return ret;
}
@@ -100,7 +100,7 @@ int cpu_pm_enter(void)
int nr_calls;
int ret = 0;
- read_lock(&cpu_pm_notifier_lock);
+ raw_spin_lock(&cpu_pm_notifier_lock);
ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
if (ret)
/*
@@ -108,7 +108,7 @@ int cpu_pm_enter(void)
* PM entry who are notified earlier to prepare for it.
*/
cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
- read_unlock(&cpu_pm_notifier_lock);
+ raw_spin_unlock(&cpu_pm_notifier_lock);
return ret;
}
@@ -130,9 +130,9 @@ int cpu_pm_exit(void)
{
int ret;
- read_lock(&cpu_pm_notifier_lock);
+ raw_spin_lock(&cpu_pm_notifier_lock);
ret = cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
- read_unlock(&cpu_pm_notifier_lock);
+ raw_spin_unlock(&cpu_pm_notifier_lock);
return ret;
}
@@ -159,7 +159,7 @@ int cpu_cluster_pm_enter(void)
int nr_calls;
int ret = 0;
- read_lock(&cpu_pm_notifier_lock);
+ raw_spin_lock(&cpu_pm_notifier_lock);
ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
if (ret)
/*
@@ -167,7 +167,7 @@ int cpu_cluster_pm_enter(void)
* PM entry who are notified earlier to prepare for it.
*/
cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
- read_unlock(&cpu_pm_notifier_lock);
+ raw_spin_unlock(&cpu_pm_notifier_lock);
return ret;
}
@@ -192,9 +192,9 @@ int cpu_cluster_pm_exit(void)
{
int ret;
- read_lock(&cpu_pm_notifier_lock);
+ raw_spin_lock(&cpu_pm_notifier_lock);
ret = cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
- read_unlock(&cpu_pm_notifier_lock);
+ raw_spin_unlock(&cpu_pm_notifier_lock);
return ret;
}
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock
2017-06-14 13:22 [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Alex Shi
@ 2017-06-16 3:12 ` Alex Shi
2017-06-16 15:40 ` Sebastian Andrzej Siewior
1 sibling, 0 replies; 3+ messages in thread
From: Alex Shi @ 2017-06-16 3:12 UTC (permalink / raw)
To: open list, linux-rt-users
Cc: Sebastian Andrzej Siewior, Thomas Gleixner, Anders Roxell,
Daniel Lezcano
It's a serious bug which cause arm/arm64 rt boot failed.
Anyone like to give a glance?
Thanks
Alex
On 06/14/2017 09:22 PM, Alex Shi wrote:
> This is a quick fix for a bug as 'scheduling while atomic' or
> 'scheduling from the idle thread' on arm/arm64.
>
> On arm/arm64, rwlock cpu_pm_notifier_lock in cpu_pm cause a potential
> schedule after irq disable in 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.
> I also tried use local_lock_irq to replace local_irq_disable, but my 2
> boards just die without any output. So maybe it's only quick way to
> make rt kernel work on arm/arm64.
>
> Since this is quick fix, instead of split out the raw rwlock, to use
> raw_spin_lock is simple and don't cost much.
>
> Signed-off-by: Alex Shi <alex.shi@linaro.org>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Anders Roxell <anders.roxell@linaro.org>
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
> ---
> kernel/cpu_pm.c | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
> index 009cc9a..8ffa13e3 100644
> --- a/kernel/cpu_pm.c
> +++ b/kernel/cpu_pm.c
> @@ -22,7 +22,7 @@
> #include <linux/spinlock.h>
> #include <linux/syscore_ops.h>
>
> -static DEFINE_RWLOCK(cpu_pm_notifier_lock);
> +static DEFINE_RAW_SPINLOCK(cpu_pm_notifier_lock);
> static RAW_NOTIFIER_HEAD(cpu_pm_notifier_chain);
>
> static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
> @@ -50,9 +50,9 @@ int cpu_pm_register_notifier(struct notifier_block *nb)
> unsigned long flags;
> int ret;
>
> - write_lock_irqsave(&cpu_pm_notifier_lock, flags);
> + raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
> ret = raw_notifier_chain_register(&cpu_pm_notifier_chain, nb);
> - write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
> + raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
>
> return ret;
> }
> @@ -72,9 +72,9 @@ int cpu_pm_unregister_notifier(struct notifier_block *nb)
> unsigned long flags;
> int ret;
>
> - write_lock_irqsave(&cpu_pm_notifier_lock, flags);
> + raw_spin_lock_irqsave(&cpu_pm_notifier_lock, flags);
> ret = raw_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
> - write_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
> + raw_spin_unlock_irqrestore(&cpu_pm_notifier_lock, flags);
>
> return ret;
> }
> @@ -100,7 +100,7 @@ int cpu_pm_enter(void)
> int nr_calls;
> int ret = 0;
>
> - read_lock(&cpu_pm_notifier_lock);
> + raw_spin_lock(&cpu_pm_notifier_lock);
> ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
> if (ret)
> /*
> @@ -108,7 +108,7 @@ int cpu_pm_enter(void)
> * PM entry who are notified earlier to prepare for it.
> */
> cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
> - read_unlock(&cpu_pm_notifier_lock);
> + raw_spin_unlock(&cpu_pm_notifier_lock);
>
> return ret;
> }
> @@ -130,9 +130,9 @@ int cpu_pm_exit(void)
> {
> int ret;
>
> - read_lock(&cpu_pm_notifier_lock);
> + raw_spin_lock(&cpu_pm_notifier_lock);
> ret = cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
> - read_unlock(&cpu_pm_notifier_lock);
> + raw_spin_unlock(&cpu_pm_notifier_lock);
>
> return ret;
> }
> @@ -159,7 +159,7 @@ int cpu_cluster_pm_enter(void)
> int nr_calls;
> int ret = 0;
>
> - read_lock(&cpu_pm_notifier_lock);
> + raw_spin_lock(&cpu_pm_notifier_lock);
> ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
> if (ret)
> /*
> @@ -167,7 +167,7 @@ int cpu_cluster_pm_enter(void)
> * PM entry who are notified earlier to prepare for it.
> */
> cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
> - read_unlock(&cpu_pm_notifier_lock);
> + raw_spin_unlock(&cpu_pm_notifier_lock);
>
> return ret;
> }
> @@ -192,9 +192,9 @@ int cpu_cluster_pm_exit(void)
> {
> int ret;
>
> - read_lock(&cpu_pm_notifier_lock);
> + raw_spin_lock(&cpu_pm_notifier_lock);
> ret = cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
> - read_unlock(&cpu_pm_notifier_lock);
> + raw_spin_unlock(&cpu_pm_notifier_lock);
>
> return ret;
> }
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock
2017-06-14 13:22 [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Alex Shi
2017-06-16 3:12 ` Alex Shi
@ 2017-06-16 15:40 ` Sebastian Andrzej Siewior
1 sibling, 0 replies; 3+ messages in thread
From: Sebastian Andrzej Siewior @ 2017-06-16 15:40 UTC (permalink / raw)
To: Alex Shi
Cc: open list, Thomas Gleixner, Anders Roxell, Daniel Lezcano,
linux-rt-users
On 2017-06-14 21:22:19 [+0800], Alex Shi wrote:
> This is a quick fix for a bug as 'scheduling while atomic' or
> 'scheduling from the idle thread' on arm/arm64.
>
> On arm/arm64, rwlock cpu_pm_notifier_lock in cpu_pm cause a potential
> schedule after irq disable in 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.
> I also tried use local_lock_irq to replace local_irq_disable, but my 2
> boards just die without any output. So maybe it's only quick way to
> make rt kernel work on arm/arm64.
>
> Since this is quick fix, instead of split out the raw rwlock, to use
> raw_spin_lock is simple and don't cost much.
I must have it disabled on my juno64 (and my 32bit boxes) since I
haven't seen it.
So we end up in IRQ off section and can't do anything about it. So
DEFINE_RAW_SPINLOCK it is? Can we have this upstream, please? Or is that
reader/writer part *so* important? If so would it work to move that part
to atomic_notifier_*() and have rcu_read_lock() instead that
read_lock()?
Sebastian
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-06-14 13:22 [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Alex Shi
2017-06-16 3:12 ` Alex Shi
2017-06-16 15:40 ` Sebastian Andrzej Siewior
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