Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1665825 > unrolled thread

[RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock

Started byAlex Shi <alex.shi@linaro.org>
First post2017-06-14 15:30 +0200
Last post2017-06-16 17:50 +0200
Articles 3 — 2 participants

Back to article view | Back to linux.kernel

Contents

  [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Alex Shi <alex.shi@linaro.org> - 2017-06-14 15:30 +0200
    Re: [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Alex Shi <alex.shi@linaro.org> - 2017-06-16 05:20 +0200
    Re: [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2017-06-16 17:50 +0200

#1665825 — [RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock

FromAlex Shi <alex.shi@linaro.org>
Date2017-06-14 15:30 +0200
Subject[RFC PATCH] cpu_pm/rt: replace rt rwlock with raw spinlock
Message-ID<tSgwW-5I4-7@gated-at.bofh.it>
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

[toc] | [next] | [standalone]

#1667396

FromAlex Shi <alex.shi@linaro.org>
Date2017-06-16 05:20 +0200
Message-ID<tSPXI-2Wr-5@gated-at.bofh.it>
In reply to#1665825
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;
>  }
>

[toc] | [prev] | [next] | [standalone]

#1667840

FromSebastian Andrzej Siewior <bigeasy@linutronix.de>
Date2017-06-16 17:50 +0200
Message-ID<tT1Fv-1ZE-7@gated-at.bofh.it>
In reply to#1665825
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

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web