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[PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled

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  [PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled Qi Hou <qi.hou@windriver.com> - 2017-03-13 11:20 +0100
    Re: [PATCH] lockdep: call trace_hardirqs_off after clearing  hardirqs_enabled Steven Rostedt <rostedt@goodmis.org> - 2017-03-13 15:10 +0100
      Re: [PATCH] lockdep: call trace_hardirqs_off after clearing  hardirqs_enabled qhou <qi.hou@windriver.com> - 2017-03-14 02:30 +0100
    Re: [PATCH] lockdep: call trace_hardirqs_off after clearing  hardirqs_enabled Peter Zijlstra <peterz@infradead.org> - 2017-03-13 15:40 +0100

#1599176 — [PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled

The current order of calls within trace_hardirqs_off() would provoke an
"unannotated irqs-off" WARNING.

This warning was reported by check_flags() when it found that the hardirqs has
been disabled but the irq-flags state, hardirqs_enabled, has not been cleared.

Check_flags() is called via trace_hardirqs_off(), and trace_hardirqs_off() will
be called by functions kind of local_irq_disable() if CONFIG_TRACE_IRQFLAGS has
been enabled.

The calltrace from functions kind of local_irq_diasble() to check_flags()
simplied as below:

local_irq_disable()
 |- trace_hardirqs_off()
     |- trace_hardirqs_off_caller()
         |- preemptirqsoff_hist()
            |- __DO_TRACE()
               |- rcu_dereference_sched()
                   |- rcu_read_lock_sched_held()
                       |- lock_is_held()
                           |- check_flags()

The order of calls within trace_hardirqs_off() can be simplified as below:

local_irq_disable()
 |- raw_local_irq_disable()
 |- trace_hardirqs_off()
     |- trace_hardirqs_off() --> check_flags()
     |- hardirqs_enabled = 0

We could find that the call to check_flags() has been made between disabling
hardirqs and clearing hardirqs_enabled. That will definitely cause an
"unannotated irqs-off" warning.

To fix this "unannotated irqs-off" warning, we must call trace_hardirqs_off()
after that we clear hardirqs_enabled.

Signed-off-by: Qi Hou <qi.hou@windriver.com>
---
 kernel/locking/lockdep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 577f026..e8b35e4 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2627,8 +2627,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	time_hardirqs_off(CALLER_ADDR0, ip);
-
 	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
@@ -2649,6 +2647,8 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
 		debug_atomic_inc(hardirqs_off_events);
 	} else
 		debug_atomic_inc(redundant_hardirqs_off);
+
+	time_hardirqs_off(CALLER_ADDR0, ip);
 }
 EXPORT_SYMBOL(trace_hardirqs_off_caller);
 
-- 
1.9.1

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#1599409 — Re: [PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled

On Mon, 13 Mar 2017 18:08:48 +0800
Qi Hou <qi.hou@windriver.com> wrote:

> The current order of calls within trace_hardirqs_off() would provoke an
> "unannotated irqs-off" WARNING.
> 
> This warning was reported by check_flags() when it found that the hardirqs has
> been disabled but the irq-flags state, hardirqs_enabled, has not been cleared.
> 
> Check_flags() is called via trace_hardirqs_off(), and trace_hardirqs_off() will
> be called by functions kind of local_irq_disable() if CONFIG_TRACE_IRQFLAGS has
> been enabled.
> 
> The calltrace from functions kind of local_irq_diasble() to check_flags()
> simplied as below:
> 
> local_irq_disable()
>  |- trace_hardirqs_off()
>      |- trace_hardirqs_off_caller()
>          |- preemptirqsoff_hist()

There is no preemptirqsoff_hist() function in the kernel.

-- Steve

>             |- __DO_TRACE()
>                |- rcu_dereference_sched()
>                    |- rcu_read_lock_sched_held()
>                        |- lock_is_held()
>                            |- check_flags()
> 
> The order of calls within trace_hardirqs_off() can be simplified as below:
> 
> local_irq_disable()
>  |- raw_local_irq_disable()
>  |- trace_hardirqs_off()
>      |- trace_hardirqs_off() --> check_flags()
>      |- hardirqs_enabled = 0
> 
> We could find that the call to check_flags() has been made between disabling
> hardirqs and clearing hardirqs_enabled. That will definitely cause an
> "unannotated irqs-off" warning.
> 
> To fix this "unannotated irqs-off" warning, we must call trace_hardirqs_off()
> after that we clear hardirqs_enabled.
> 
> Signed-off-by: Qi Hou <qi.hou@windriver.com>
> ---
>  kernel/locking/lockdep.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 577f026..e8b35e4 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -2627,8 +2627,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
>  {
>  	struct task_struct *curr = current;
>  
> -	time_hardirqs_off(CALLER_ADDR0, ip);
> -
>  	if (unlikely(!debug_locks || current->lockdep_recursion))
>  		return;
>  
> @@ -2649,6 +2647,8 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
>  		debug_atomic_inc(hardirqs_off_events);
>  	} else
>  		debug_atomic_inc(redundant_hardirqs_off);
> +
> +	time_hardirqs_off(CALLER_ADDR0, ip);
>  }
>  EXPORT_SYMBOL(trace_hardirqs_off_caller);
>  

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#1599969 — Re: [PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled

On 2017年03月13日 22:05, Steven Rostedt wrote:
> On Mon, 13 Mar 2017 18:08:48 +0800
> Qi Hou <qi.hou@windriver.com> wrote:
>
>> The current order of calls within trace_hardirqs_off() would provoke an
>> "unannotated irqs-off" WARNING.
>>
>> This warning was reported by check_flags() when it found that the hardirqs has
>> been disabled but the irq-flags state, hardirqs_enabled, has not been cleared.
>>
>> Check_flags() is called via trace_hardirqs_off(), and trace_hardirqs_off() will
>> be called by functions kind of local_irq_disable() if CONFIG_TRACE_IRQFLAGS has
>> been enabled.
>>
>> The calltrace from functions kind of local_irq_diasble() to check_flags()
>> simplied as below:
>>
>> local_irq_disable()
>>   |- trace_hardirqs_off()
>>       |- trace_hardirqs_off_caller()
>>           |- preemptirqsoff_hist()
> There is no preemptirqsoff_hist() function in the kernel.
Sorry, it's a mistake. It should have been 
"trace_hardirqs_off_caller()", defined in file
kernel/locking/lockdep.c.

And it will call trace_preemptirqsoff_hist_rcuidle(), 
trace_preemptirqsoff_hist_rcuidle will()
call check_flags().

I will correct it. And after carefully checking the patch, I will 
re-send it.

Very very sorry for my mistake. That wasted your time.

---
Best regards,
Qi Hou
>
> -- Steve
>
>>              |- __DO_TRACE()
>>                 |- rcu_dereference_sched()
>>                     |- rcu_read_lock_sched_held()
>>                         |- lock_is_held()
>>                             |- check_flags()
>>
>> The order of calls within trace_hardirqs_off() can be simplified as below:
>>
>> local_irq_disable()
>>   |- raw_local_irq_disable()
>>   |- trace_hardirqs_off()
>>       |- trace_hardirqs_off() --> check_flags()
>>       |- hardirqs_enabled = 0
>>
>> We could find that the call to check_flags() has been made between disabling
>> hardirqs and clearing hardirqs_enabled. That will definitely cause an
>> "unannotated irqs-off" warning.
>>
>> To fix this "unannotated irqs-off" warning, we must call trace_hardirqs_off()
>> after that we clear hardirqs_enabled.
>>
>> Signed-off-by: Qi Hou <qi.hou@windriver.com>
>> ---
>>   kernel/locking/lockdep.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
>> index 577f026..e8b35e4 100644
>> --- a/kernel/locking/lockdep.c
>> +++ b/kernel/locking/lockdep.c
>> @@ -2627,8 +2627,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
>>   {
>>   	struct task_struct *curr = current;
>>   
>> -	time_hardirqs_off(CALLER_ADDR0, ip);
>> -
>>   	if (unlikely(!debug_locks || current->lockdep_recursion))
>>   		return;
>>   
>> @@ -2649,6 +2647,8 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
>>   		debug_atomic_inc(hardirqs_off_events);
>>   	} else
>>   		debug_atomic_inc(redundant_hardirqs_off);
>> +
>> +	time_hardirqs_off(CALLER_ADDR0, ip);
>>   }
>>   EXPORT_SYMBOL(trace_hardirqs_off_caller);
>>   

-- 
Best regards,
Qi Hou
Phone number: +86-10-8477-8608
Address: Floor 15, Building B, Wangjing Plaza, No.9 Zhong-Huan Nanlu, Chaoyang District

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#1599457 — Re: [PATCH] lockdep: call trace_hardirqs_off after clearing hardirqs_enabled

Thanks for Cc'ing me.

On Mon, Mar 13, 2017 at 06:08:48PM +0800, Qi Hou wrote:
> The current order of calls within trace_hardirqs_off() would provoke an
> "unannotated irqs-off" WARNING.
> 
> This warning was reported by check_flags() when it found that the hardirqs has
> been disabled but the irq-flags state, hardirqs_enabled, has not been cleared.
> 
> Check_flags() is called via trace_hardirqs_off(), and trace_hardirqs_off() will
> be called by functions kind of local_irq_disable() if CONFIG_TRACE_IRQFLAGS has
> been enabled.
> 
> The calltrace from functions kind of local_irq_diasble() to check_flags()
> simplied as below:
> 
> local_irq_disable()
>  |- trace_hardirqs_off()
>      |- trace_hardirqs_off_caller()
>          |- preemptirqsoff_hist()
>             |- __DO_TRACE()
>                |- rcu_dereference_sched()
>                    |- rcu_read_lock_sched_held()
>                        |- lock_is_held()
>                            |- check_flags()
> 
> The order of calls within trace_hardirqs_off() can be simplified as below:
> 
> local_irq_disable()
>  |- raw_local_irq_disable()
>  |- trace_hardirqs_off()
>      |- trace_hardirqs_off() --> check_flags()
>      |- hardirqs_enabled = 0
> 
> We could find that the call to check_flags() has been made between disabling
> hardirqs and clearing hardirqs_enabled. That will definitely cause an
> "unannotated irqs-off" warning.
> 
> To fix this "unannotated irqs-off" warning, we must call trace_hardirqs_off()
> after that we clear hardirqs_enabled.

Here you say: "trace_hardirqs_off()"

> Signed-off-by: Qi Hou <qi.hou@windriver.com>
> ---
>  kernel/locking/lockdep.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 577f026..e8b35e4 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -2627,8 +2627,6 @@ __visible void trace_hardirqs_off_caller(unsigned long ip)
>  {
>  	struct task_struct *curr = current;
>  
> -	time_hardirqs_off(CALLER_ADDR0, ip);

This is: "TIME_hardirqs_off()", notice the difference?

Care to try to write a changelog that makes sense?

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