[PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Takao Indoh]

Hi all,

This patch renames init_call_single_data() to call_function_init() and
calls it in start_kernel() so that call_single_queue can be initialized
before enabling interrupt.

There is a problem that kdump(2nd kernel) sometimes hangs up due to
pending IPI from 1st kernel. Kernel panic occurs because IPI comes
before call_single_queue is initialized. The details are as follows.
(1) 2nd kernel boot up
(2) A pending IPI from 1st kernel comes when irqs are first enabled
    in start_kernel().
(3) Kernel tries to handle the interrupt, but call_single_queue is not
    initialized yet at this point. As a result, in the
    generic_smp_call_function_single_interrupt(), NULL pointer
    dereference occurs when list_replace_init() tries to access
    &q->list.next.
Therefore this patch changes the name of init_call_single_data() to
call_function_init() and calls it before local_irq_enable() in
start_kernel().

v2:
- Rename init_call_single_data() to call_function_init() and calls it in
  start_kernel()
- Change insert position in start_kernel().
- Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
- Rebased to Linus's latest tree

v1:
https://lkml.org/lkml/2011/3/25/317
- Divide init_call_single_data() into two functions,
   o init_call_single_data: initialize call_single_queue
   o init_hotplug_cfd: initialize hotplug_cfd_notifier
  And call init_call_single_data before local_irq_enable() in
  start_kernel().

v0:
https://lkml.org/lkml/2011/3/23/417
- In generic_smp_call_function_single_interrupt(), check if
  call_single_queue was initialized or not, and just return if not
  initialized.

Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
---
 include/linux/smp.h |    5 ++++-
 init/main.c         |    1 +
 kernel/smp.c        |    5 +----
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 74243c8..4fb3eac 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
  * Generic and arch helpers
  */
 #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
+void __init call_function_init(void);
 void generic_smp_call_function_single_interrupt(void);
 void generic_smp_call_function_interrupt(void);
 void ipi_call_lock(void);
 void ipi_call_unlock(void);
 void ipi_call_lock_irq(void);
 void ipi_call_unlock_irq(void);
+#else
+static inline void call_function_init(void) { }
 #endif
 
 /*
@@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
 #define smp_prepare_boot_cpu()			do {} while (0)
 #define smp_call_function_many(mask, func, info, wait) \
 			(up_smp_call_function(func, info))
-static inline void init_call_single_data(void) { }
+static inline void call_function_init(void) { }
 
 static inline int
 smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
diff --git a/init/main.c b/init/main.c
index 4a9479e..12821d1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
 	timekeeping_init();
 	time_init();
 	profile_init();
+	call_function_init();
 	if (!irqs_disabled())
 		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
 				 "enabled early\n");
diff --git a/kernel/smp.c b/kernel/smp.c
index 73a1951..fb67dfa 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
 	.notifier_call		= hotplug_cfd,
 };
 
-static int __cpuinit init_call_single_data(void)
+void __init call_function_init(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
 	int i;
@@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
 
 	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
 	register_cpu_notifier(&hotplug_cfd_notifier);
-
-	return 0;
 }
-early_initcall(init_call_single_data);
 
 /*
  * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Américo Wang]

On Wed, Mar 30, 2011 at 12:35 AM, Takao Indoh
<indou.takao@jp.fujitsu.com> wrote:
> Hi all,
>
> This patch renames init_call_single_data() to call_function_init() and
> calls it in start_kernel() so that call_single_queue can be initialized
> before enabling interrupt.
>
> There is a problem that kdump(2nd kernel) sometimes hangs up due to
> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
> before call_single_queue is initialized. The details are as follows.
> (1) 2nd kernel boot up
> (2) A pending IPI from 1st kernel comes when irqs are first enabled
>    in start_kernel().
> (3) Kernel tries to handle the interrupt, but call_single_queue is not
>    initialized yet at this point. As a result, in the
>    generic_smp_call_function_single_interrupt(), NULL pointer
>    dereference occurs when list_replace_init() tries to access
>    &q->list.next.
> Therefore this patch changes the name of init_call_single_data() to
> call_function_init() and calls it before local_irq_enable() in
> start_kernel().
>
> v2:
> - Rename init_call_single_data() to call_function_init() and calls it in
>  start_kernel()
> - Change insert position in start_kernel().
> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
> - Rebased to Linus's latest tree
>

Looks good to my eyes,

Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>

Thanks.

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Neil Horman]

On Tue, Mar 29, 2011 at 12:35:04PM -0400, Takao Indoh wrote:
> Hi all,
> 
> This patch renames init_call_single_data() to call_function_init() and
> calls it in start_kernel() so that call_single_queue can be initialized
> before enabling interrupt.
> 
> There is a problem that kdump(2nd kernel) sometimes hangs up due to
> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
> before call_single_queue is initialized. The details are as follows.
> (1) 2nd kernel boot up
> (2) A pending IPI from 1st kernel comes when irqs are first enabled
>     in start_kernel().
> (3) Kernel tries to handle the interrupt, but call_single_queue is not
>     initialized yet at this point. As a result, in the
>     generic_smp_call_function_single_interrupt(), NULL pointer
>     dereference occurs when list_replace_init() tries to access
>     &q->list.next.
> Therefore this patch changes the name of init_call_single_data() to
> call_function_init() and calls it before local_irq_enable() in
> start_kernel().
> 
> v2:
> - Rename init_call_single_data() to call_function_init() and calls it in
>   start_kernel()
> - Change insert position in start_kernel().
> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
> - Rebased to Linus's latest tree
> 
> v1:
> https://lkml.org/lkml/2011/3/25/317
> - Divide init_call_single_data() into two functions,
>    o init_call_single_data: initialize call_single_queue
>    o init_hotplug_cfd: initialize hotplug_cfd_notifier
>   And call init_call_single_data before local_irq_enable() in
>   start_kernel().
> 
> v0:
> https://lkml.org/lkml/2011/3/23/417
> - In generic_smp_call_function_single_interrupt(), check if
>   call_single_queue was initialized or not, and just return if not
>   initialized.
> 
> Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
> ---
>  include/linux/smp.h |    5 ++++-
>  init/main.c         |    1 +
>  kernel/smp.c        |    5 +----
>  3 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/smp.h b/include/linux/smp.h
> index 74243c8..4fb3eac 100644
> --- a/include/linux/smp.h
> +++ b/include/linux/smp.h
> @@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
>   * Generic and arch helpers
>   */
>  #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
> +void __init call_function_init(void);
>  void generic_smp_call_function_single_interrupt(void);
>  void generic_smp_call_function_interrupt(void);
>  void ipi_call_lock(void);
>  void ipi_call_unlock(void);
>  void ipi_call_lock_irq(void);
>  void ipi_call_unlock_irq(void);
> +#else
> +static inline void call_function_init(void) { }
>  #endif
>  
>  /*
> @@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
>  #define smp_prepare_boot_cpu()			do {} while (0)
>  #define smp_call_function_many(mask, func, info, wait) \
>  			(up_smp_call_function(func, info))
> -static inline void init_call_single_data(void) { }
> +static inline void call_function_init(void) { }
>  
>  static inline int
>  smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
> diff --git a/init/main.c b/init/main.c
> index 4a9479e..12821d1 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
>  	timekeeping_init();
>  	time_init();
>  	profile_init();
> +	call_function_init();
>  	if (!irqs_disabled())
>  		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
>  				 "enabled early\n");
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 73a1951..fb67dfa 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
>  	.notifier_call		= hotplug_cfd,
>  };
>  
> -static int __cpuinit init_call_single_data(void)
> +void __init call_function_init(void)
>  {
>  	void *cpu = (void *)(long)smp_processor_id();
>  	int i;
> @@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
>  
>  	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
>  	register_cpu_notifier(&hotplug_cfd_notifier);
> -
> -	return 0;
>  }
> -early_initcall(init_call_single_data);
>  
>  /*
>   * csd_lock/csd_unlock used to serialize access to per-cpu csd resources
> 
Acked-by: Neil Horman <nhorman@tuxdriver.com>

> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Vivek Goyal]

On Tue, Mar 29, 2011 at 12:35:04PM -0400, Takao Indoh wrote:
> Hi all,
> 
> This patch renames init_call_single_data() to call_function_init() and
> calls it in start_kernel() so that call_single_queue can be initialized
> before enabling interrupt.
> 
> There is a problem that kdump(2nd kernel) sometimes hangs up due to
> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
> before call_single_queue is initialized. The details are as follows.
> (1) 2nd kernel boot up
> (2) A pending IPI from 1st kernel comes when irqs are first enabled
>     in start_kernel().
> (3) Kernel tries to handle the interrupt, but call_single_queue is not
>     initialized yet at this point. As a result, in the
>     generic_smp_call_function_single_interrupt(), NULL pointer
>     dereference occurs when list_replace_init() tries to access
>     &q->list.next.
> Therefore this patch changes the name of init_call_single_data() to
> call_function_init() and calls it before local_irq_enable() in
> start_kernel().
> 
> v2:
> - Rename init_call_single_data() to call_function_init() and calls it in
>   start_kernel()
> - Change insert position in start_kernel().
> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
> - Rebased to Linus's latest tree
> 
> v1:
> https://lkml.org/lkml/2011/3/25/317
> - Divide init_call_single_data() into two functions,
>    o init_call_single_data: initialize call_single_queue
>    o init_hotplug_cfd: initialize hotplug_cfd_notifier
>   And call init_call_single_data before local_irq_enable() in
>   start_kernel().
> 
> v0:
> https://lkml.org/lkml/2011/3/23/417
> - In generic_smp_call_function_single_interrupt(), check if
>   call_single_queue was initialized or not, and just return if not
>   initialized.
> 
> Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
> ---
>  include/linux/smp.h |    5 ++++-
>  init/main.c         |    1 +
>  kernel/smp.c        |    5 +----
>  3 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/smp.h b/include/linux/smp.h
> index 74243c8..4fb3eac 100644
> --- a/include/linux/smp.h
> +++ b/include/linux/smp.h
> @@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
>   * Generic and arch helpers
>   */
>  #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
> +void __init call_function_init(void);
>  void generic_smp_call_function_single_interrupt(void);
>  void generic_smp_call_function_interrupt(void);
>  void ipi_call_lock(void);
>  void ipi_call_unlock(void);
>  void ipi_call_lock_irq(void);
>  void ipi_call_unlock_irq(void);
> +#else
> +static inline void call_function_init(void) { }
>  #endif
>  
>  /*
> @@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
>  #define smp_prepare_boot_cpu()			do {} while (0)
>  #define smp_call_function_many(mask, func, info, wait) \
>  			(up_smp_call_function(func, info))
> -static inline void init_call_single_data(void) { }
> +static inline void call_function_init(void) { }
>  
>  static inline int
>  smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
> diff --git a/init/main.c b/init/main.c
> index 4a9479e..12821d1 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
>  	timekeeping_init();
>  	time_init();
>  	profile_init();
> +	call_function_init();

Takao,

So by calling this function before we enable interrupts we have made
sure that per cpu call_single_queue has been initialized and q->list
also has been initiliazed and it is an empty list now.

After enabling the interrupts, I am assuming we will call
generic_smp_call_function_single_interrupt().

this function does.

        raw_spin_lock(&q->lock);
        list_replace_init(&q->list, &list);
        raw_spin_unlock(&q->lock);

        while (!list_empty(&list)) {
                struct call_single_data *data;

                data = list_entry(list.next, struct call_single_data,
list);
                list_del(&data->list);

Looking at the code of list_replace_init(), I think we will have odd
results if q->list is empty. Looks like list->next will be pointing to
&q->list?

IIUC, q->list sould be empty when we get pending IPI from previous kernel
because any function scheduled for execution must have been inserted on
previous kernel's data structures and here we are building fresh data
structures.

If that is the case, I think above code should have weared interaction.
We should think that "list" is not empty and try to execute a data item
q->list which is actually not a data item.

What am I missing here. After your patch, have to debugged it and 
noticed how list_replace_init() does on empty lists and what's the
result of list_empty(list)?

Thanks
Vivek
 


>  	if (!irqs_disabled())
>  		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
>  				 "enabled early\n");
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 73a1951..fb67dfa 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
>  	.notifier_call		= hotplug_cfd,
>  };
>  
> -static int __cpuinit init_call_single_data(void)
> +void __init call_function_init(void)
>  {
>  	void *cpu = (void *)(long)smp_processor_id();
>  	int i;
> @@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
>  
>  	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
>  	register_cpu_notifier(&hotplug_cfd_notifier);
> -
> -	return 0;
>  }
> -early_initcall(init_call_single_data);
>  
>  /*
>   * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Takao Indoh]

On Wed, 6 Apr 2011 16:47:42 -0400, Vivek Goyal wrote:

>On Tue, Mar 29, 2011 at 12:35:04PM -0400, Takao Indoh wrote:
>> Hi all,
>> 
>> This patch renames init_call_single_data() to call_function_init() and
>> calls it in start_kernel() so that call_single_queue can be initialized
>> before enabling interrupt.
>> 
>> There is a problem that kdump(2nd kernel) sometimes hangs up due to
>> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
>> before call_single_queue is initialized. The details are as follows.
>> (1) 2nd kernel boot up
>> (2) A pending IPI from 1st kernel comes when irqs are first enabled
>>     in start_kernel().
>> (3) Kernel tries to handle the interrupt, but call_single_queue is not
>>     initialized yet at this point. As a result, in the
>>     generic_smp_call_function_single_interrupt(), NULL pointer
>>     dereference occurs when list_replace_init() tries to access
>>     &q->list.next.
>> Therefore this patch changes the name of init_call_single_data() to
>> call_function_init() and calls it before local_irq_enable() in
>> start_kernel().
>> 
>> v2:
>> - Rename init_call_single_data() to call_function_init() and calls it in
>>   start_kernel()
>> - Change insert position in start_kernel().
>> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
>> - Rebased to Linus's latest tree
>> 
>> v1:
>> https://lkml.org/lkml/2011/3/25/317
>> - Divide init_call_single_data() into two functions,
>>    o init_call_single_data: initialize call_single_queue
>>    o init_hotplug_cfd: initialize hotplug_cfd_notifier
>>   And call init_call_single_data before local_irq_enable() in
>>   start_kernel().
>> 
>> v0:
>> https://lkml.org/lkml/2011/3/23/417
>> - In generic_smp_call_function_single_interrupt(), check if
>>   call_single_queue was initialized or not, and just return if not
>>   initialized.
>> 
>> Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
>> ---
>>  include/linux/smp.h |    5 ++++-
>>  init/main.c         |    1 +
>>  kernel/smp.c        |    5 +----
>>  3 files changed, 6 insertions(+), 5 deletions(-)
>> 
>> diff --git a/include/linux/smp.h b/include/linux/smp.h
>> index 74243c8..4fb3eac 100644
>> --- a/include/linux/smp.h
>> +++ b/include/linux/smp.h
>> @@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
>>   * Generic and arch helpers
>>   */
>>  #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
>> +void __init call_function_init(void);
>>  void generic_smp_call_function_single_interrupt(void);
>>  void generic_smp_call_function_interrupt(void);
>>  void ipi_call_lock(void);
>>  void ipi_call_unlock(void);
>>  void ipi_call_lock_irq(void);
>>  void ipi_call_unlock_irq(void);
>> +#else
>> +static inline void call_function_init(void) { }
>>  #endif
>>  
>>  /*
>> @@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
>>  #define smp_prepare_boot_cpu()			do {} while (0)
>>  #define smp_call_function_many(mask, func, info, wait) \
>>  			(up_smp_call_function(func, info))
>> -static inline void init_call_single_data(void) { }
>> +static inline void call_function_init(void) { }
>>  
>>  static inline int
>>  smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
>> diff --git a/init/main.c b/init/main.c
>> index 4a9479e..12821d1 100644
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
>>  	timekeeping_init();
>>  	time_init();
>>  	profile_init();
>> +	call_function_init();
>
>Takao,
>
>So by calling this function before we enable interrupts we have made
>sure that per cpu call_single_queue has been initialized and q->list
>also has been initiliazed and it is an empty list now.
>
>After enabling the interrupts, I am assuming we will call
>generic_smp_call_function_single_interrupt().
>
>this function does.
>
>        raw_spin_lock(&q->lock);
>        list_replace_init(&q->list, &list);
>        raw_spin_unlock(&q->lock);
>
>        while (!list_empty(&list)) {
>                struct call_single_data *data;
>
>                data = list_entry(list.next, struct call_single_data,
>list);
>                list_del(&data->list);
>
>Looking at the code of list_replace_init(), I think we will have odd
>results if q->list is empty. Looks like list->next will be pointing to
>&q->list?
>
>IIUC, q->list sould be empty when we get pending IPI from previous kernel
>because any function scheduled for execution must have been inserted on
>previous kernel's data structures and here we are building fresh data
>structures.
>
>If that is the case, I think above code should have weared interaction.
>We should think that "list" is not empty and try to execute a data item
>q->list which is actually not a data item.
>
>What am I missing here. After your patch, have to debugged it and 
>noticed how list_replace_init() does on empty lists and what's the
>result of list_empty(list)?

When list_replace_init(&q->list, &list) is called,
they are changed as followed.

/* list_replace */
(A) &list->next = &q->list->next;
(B) &list->next->prev = &list;
(C) &list->prev = &q->list->prev;
(D) &list->prev->next = &list;

/* INIT_LIST_HEAD */
(E) &q->list->next = &q->list;
(F) &q->list->prev = &q->list;

So, if q->list is empty, each list is changed like this.

(Initial state)
list.next ==> &list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &q->list

(A)
list.next ==> &q->list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &q->list

(B)
list.next ==> &q->list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &list

(C)
list.next ==> &q->list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &list

(D)
list.next ==> &list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &list

(E)
list.next ==> &list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &list

(F)
list.next ==> &list
list.prev ==> &list
q->list.next ==> &q->list
q->list.prev ==> &q->list


So, list_empty(list)? is always false, if I am not missing something.

Thanks,
Takao Indoh

>
>Thanks
>Vivek
> 
>
>
>>  	if (!irqs_disabled())
>>  		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
>>  				 "enabled early\n");
>> diff --git a/kernel/smp.c b/kernel/smp.c
>> index 73a1951..fb67dfa 100644
>> --- a/kernel/smp.c
>> +++ b/kernel/smp.c
>> @@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata 
>> hotplug_cfd_notifier = {
>>  	.notifier_call		= hotplug_cfd,
>>  };
>>  
>> -static int __cpuinit init_call_single_data(void)
>> +void __init call_function_init(void)
>>  {
>>  	void *cpu = (void *)(long)smp_processor_id();
>>  	int i;
>> @@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
>>  
>>  	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
>>  	register_cpu_notifier(&hotplug_cfd_notifier);
>> -
>> -	return 0;
>>  }
>> -early_initcall(init_call_single_data);
>>  
>>  /*
>>   * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Takao Indoh]

On Wed, 06 Apr 2011 18:47:36 -0400, Takao Indoh wrote:

>On Wed, 6 Apr 2011 16:47:42 -0400, Vivek Goyal wrote:
>
>>On Tue, Mar 29, 2011 at 12:35:04PM -0400, Takao Indoh wrote:
>>> Hi all,
>>> 
>>> This patch renames init_call_single_data() to call_function_init() and
>>> calls it in start_kernel() so that call_single_queue can be initialized
>>> before enabling interrupt.
>>> 
>>> There is a problem that kdump(2nd kernel) sometimes hangs up due to
>>> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
>>> before call_single_queue is initialized. The details are as follows.
>>> (1) 2nd kernel boot up
>>> (2) A pending IPI from 1st kernel comes when irqs are first enabled
>>>     in start_kernel().
>>> (3) Kernel tries to handle the interrupt, but call_single_queue is not
>>>     initialized yet at this point. As a result, in the
>>>     generic_smp_call_function_single_interrupt(), NULL pointer
>>>     dereference occurs when list_replace_init() tries to access
>>>     &q->list.next.
>>> Therefore this patch changes the name of init_call_single_data() to
>>> call_function_init() and calls it before local_irq_enable() in
>>> start_kernel().
>>> 
>>> v2:
>>> - Rename init_call_single_data() to call_function_init() and calls it in
>>>   start_kernel()
>>> - Change insert position in start_kernel().
>>> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
>>> - Rebased to Linus's latest tree
>>> 
>>> v1:
>>> https://lkml.org/lkml/2011/3/25/317
>>> - Divide init_call_single_data() into two functions,
>>>    o init_call_single_data: initialize call_single_queue
>>>    o init_hotplug_cfd: initialize hotplug_cfd_notifier
>>>   And call init_call_single_data before local_irq_enable() in
>>>   start_kernel().
>>> 
>>> v0:
>>> https://lkml.org/lkml/2011/3/23/417
>>> - In generic_smp_call_function_single_interrupt(), check if
>>>   call_single_queue was initialized or not, and just return if not
>>>   initialized.
>>> 
>>> Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
>>> ---
>>>  include/linux/smp.h |    5 ++++-
>>>  init/main.c         |    1 +
>>>  kernel/smp.c        |    5 +----
>>>  3 files changed, 6 insertions(+), 5 deletions(-)
>>> 
>>> diff --git a/include/linux/smp.h b/include/linux/smp.h
>>> index 74243c8..4fb3eac 100644
>>> --- a/include/linux/smp.h
>>> +++ b/include/linux/smp.h
>>> @@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
>>>   * Generic and arch helpers
>>>   */
>>>  #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
>>> +void __init call_function_init(void);
>>>  void generic_smp_call_function_single_interrupt(void);
>>>  void generic_smp_call_function_interrupt(void);
>>>  void ipi_call_lock(void);
>>>  void ipi_call_unlock(void);
>>>  void ipi_call_lock_irq(void);
>>>  void ipi_call_unlock_irq(void);
>>> +#else
>>> +static inline void call_function_init(void) { }
>>>  #endif
>>>  
>>>  /*
>>> @@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
>>>  #define smp_prepare_boot_cpu()			do {} while (0)
>>>  #define smp_call_function_many(mask, func, info, wait) \
>>>  			(up_smp_call_function(func, info))
>>> -static inline void init_call_single_data(void) { }
>>> +static inline void call_function_init(void) { }
>>>  
>>>  static inline int
>>>  smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
>>> diff --git a/init/main.c b/init/main.c
>>> index 4a9479e..12821d1 100644
>>> --- a/init/main.c
>>> +++ b/init/main.c
>>> @@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
>>>  	timekeeping_init();
>>>  	time_init();
>>>  	profile_init();
>>> +	call_function_init();
>>
>>Takao,
>>
>>So by calling this function before we enable interrupts we have made
>>sure that per cpu call_single_queue has been initialized and q->list
>>also has been initiliazed and it is an empty list now.
>>
>>After enabling the interrupts, I am assuming we will call
>>generic_smp_call_function_single_interrupt().
>>
>>this function does.
>>
>>        raw_spin_lock(&q->lock);
>>        list_replace_init(&q->list, &list);
>>        raw_spin_unlock(&q->lock);
>>
>>        while (!list_empty(&list)) {
>>                struct call_single_data *data;
>>
>>                data = list_entry(list.next, struct call_single_data,
>>list);
>>                list_del(&data->list);
>>
>>Looking at the code of list_replace_init(), I think we will have odd
>>results if q->list is empty. Looks like list->next will be pointing to
>>&q->list?
>>
>>IIUC, q->list sould be empty when we get pending IPI from previous kernel
>>because any function scheduled for execution must have been inserted on
>>previous kernel's data structures and here we are building fresh data
>>structures.
>>
>>If that is the case, I think above code should have weared interaction.
>>We should think that "list" is not empty and try to execute a data item
>>q->list which is actually not a data item.
>>
>>What am I missing here. After your patch, have to debugged it and 
>>noticed how list_replace_init() does on empty lists and what's the
>>result of list_empty(list)?
>
>When list_replace_init(&q->list, &list) is called,
>they are changed as followed.
>
>/* list_replace */
>(A) &list->next = &q->list->next;
>(B) &list->next->prev = &list;
>(C) &list->prev = &q->list->prev;
>(D) &list->prev->next = &list;
>
>/* INIT_LIST_HEAD */
>(E) &q->list->next = &q->list;
>(F) &q->list->prev = &q->list;
>
>So, if q->list is empty, each list is changed like this.
>
>(Initial state)
>list.next ==> &list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &q->list
>
>(A)
>list.next ==> &q->list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &q->list
>
>(B)
>list.next ==> &q->list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &list
>
>(C)
>list.next ==> &q->list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &list
>
>(D)
>list.next ==> &list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &list
>
>(E)
>list.next ==> &list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &list
>
>(F)
>list.next ==> &list
>list.prev ==> &list
>q->list.next ==> &q->list
>q->list.prev ==> &q->list
>
>
>So, list_empty(list)? is always false, if I am not missing something.

No, list_empty(list)? is always *true*.

Thanks,
Takao Indoh



>>
>>Thanks
>>Vivek
>> 
>>
>>
>>>  	if (!irqs_disabled())
>>>  		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
>>>  				 "enabled early\n");
>>> diff --git a/kernel/smp.c b/kernel/smp.c
>>> index 73a1951..fb67dfa 100644
>>> --- a/kernel/smp.c
>>> +++ b/kernel/smp.c
>>> @@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata 
>>> hotplug_cfd_notifier = {
>>>  	.notifier_call		= hotplug_cfd,
>>>  };
>>>  
>>> -static int __cpuinit init_call_single_data(void)
>>> +void __init call_function_init(void)
>>>  {
>>>  	void *cpu = (void *)(long)smp_processor_id();
>>>  	int i;
>>> @@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
>>>  
>>>  	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
>>>  	register_cpu_notifier(&hotplug_cfd_notifier);
>>> -
>>> -	return 0;
>>>  }
>>> -early_initcall(init_call_single_data);
>>>  
>>>  /*
>>>   * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Vivek Goyal]

On Wed, Apr 06, 2011 at 06:52:27PM -0400, Takao Indoh wrote:
> On Wed, 06 Apr 2011 18:47:36 -0400, Takao Indoh wrote:
> 
> >On Wed, 6 Apr 2011 16:47:42 -0400, Vivek Goyal wrote:
> >
> >>On Tue, Mar 29, 2011 at 12:35:04PM -0400, Takao Indoh wrote:
> >>> Hi all,
> >>> 
> >>> This patch renames init_call_single_data() to call_function_init() and
> >>> calls it in start_kernel() so that call_single_queue can be initialized
> >>> before enabling interrupt.
> >>> 
> >>> There is a problem that kdump(2nd kernel) sometimes hangs up due to
> >>> pending IPI from 1st kernel. Kernel panic occurs because IPI comes
> >>> before call_single_queue is initialized. The details are as follows.
> >>> (1) 2nd kernel boot up
> >>> (2) A pending IPI from 1st kernel comes when irqs are first enabled
> >>>     in start_kernel().
> >>> (3) Kernel tries to handle the interrupt, but call_single_queue is not
> >>>     initialized yet at this point. As a result, in the
> >>>     generic_smp_call_function_single_interrupt(), NULL pointer
> >>>     dereference occurs when list_replace_init() tries to access
> >>>     &q->list.next.
> >>> Therefore this patch changes the name of init_call_single_data() to
> >>> call_function_init() and calls it before local_irq_enable() in
> >>> start_kernel().
> >>> 
> >>> v2:
> >>> - Rename init_call_single_data() to call_function_init() and calls it in
> >>>   start_kernel()
> >>> - Change insert position in start_kernel().
> >>> - Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
> >>> - Rebased to Linus's latest tree
> >>> 
> >>> v1:
> >>> https://lkml.org/lkml/2011/3/25/317
> >>> - Divide init_call_single_data() into two functions,
> >>>    o init_call_single_data: initialize call_single_queue
> >>>    o init_hotplug_cfd: initialize hotplug_cfd_notifier
> >>>   And call init_call_single_data before local_irq_enable() in
> >>>   start_kernel().
> >>> 
> >>> v0:
> >>> https://lkml.org/lkml/2011/3/23/417
> >>> - In generic_smp_call_function_single_interrupt(), check if
> >>>   call_single_queue was initialized or not, and just return if not
> >>>   initialized.
> >>> 
> >>> Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>

[..]
> >So, list_empty(list)? is always false, if I am not missing something.
> 
> No, list_empty(list)? is always *true*.
> 

ok, I got it. So list_replace_init() is fine even if q->list is empty. So
when a pending IPI from previous kernel comes, q->list will be empty
and we will simply do nothing. Sounds reaosnable to me.

Acked-by: Vivek Goyal <vgoyal@redhat.com>

Thanks
Vivek

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Takao Indoh]

Just a reminder...

Thanks for acks, but I'm still waiting for inclusion.
I tested 3.0.0-rc3 and kdump still failed due to pending IPI
from 1st kernel. Need this patch to fix it.

Thanks,
Takao Indoh

On Tue, 29 Mar 2011 12:35:04 -0400, Takao Indoh wrote:

>Hi all,
>
>This patch renames init_call_single_data() to call_function_init() and
>calls it in start_kernel() so that call_single_queue can be initialized
>before enabling interrupt.
>
>There is a problem that kdump(2nd kernel) sometimes hangs up due to
>pending IPI from 1st kernel. Kernel panic occurs because IPI comes
>before call_single_queue is initialized. The details are as follows.
>(1) 2nd kernel boot up
>(2) A pending IPI from 1st kernel comes when irqs are first enabled
>    in start_kernel().
>(3) Kernel tries to handle the interrupt, but call_single_queue is not
>    initialized yet at this point. As a result, in the
>    generic_smp_call_function_single_interrupt(), NULL pointer
>    dereference occurs when list_replace_init() tries to access
>    &q->list.next.
>Therefore this patch changes the name of init_call_single_data() to
>call_function_init() and calls it before local_irq_enable() in
>start_kernel().
>
>v2:
>- Rename init_call_single_data() to call_function_init() and calls it in
>  start_kernel()
>- Change insert position in start_kernel().
>- Adjust for CONFIG_SMP/CONFIG_USE_GENERIC_SMP_HELPERS options
>- Rebased to Linus's latest tree
>
>v1:
>https://lkml.org/lkml/2011/3/25/317
>- Divide init_call_single_data() into two functions,
>   o init_call_single_data: initialize call_single_queue
>   o init_hotplug_cfd: initialize hotplug_cfd_notifier
>  And call init_call_single_data before local_irq_enable() in
>  start_kernel().
>
>v0:
>https://lkml.org/lkml/2011/3/23/417
>- In generic_smp_call_function_single_interrupt(), check if
>  call_single_queue was initialized or not, and just return if not
>  initialized.
>
>Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
>---
> include/linux/smp.h |    5 ++++-
> init/main.c         |    1 +
> kernel/smp.c        |    5 +----
> 3 files changed, 6 insertions(+), 5 deletions(-)
>
>diff --git a/include/linux/smp.h b/include/linux/smp.h
>index 74243c8..4fb3eac 100644
>--- a/include/linux/smp.h
>+++ b/include/linux/smp.h
>@@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
>  * Generic and arch helpers
>  */
> #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
>+void __init call_function_init(void);
> void generic_smp_call_function_single_interrupt(void);
> void generic_smp_call_function_interrupt(void);
> void ipi_call_lock(void);
> void ipi_call_unlock(void);
> void ipi_call_lock_irq(void);
> void ipi_call_unlock_irq(void);
>+#else
>+static inline void call_function_init(void) { }
> #endif
> 
> /*
>@@ -144,7 +147,7 @@ static inline void smp_send_reschedule(int cpu) { }
> #define smp_prepare_boot_cpu()			do {} while (0)
> #define smp_call_function_many(mask, func, info, wait) \
> 			(up_smp_call_function(func, info))
>-static inline void init_call_single_data(void) { }
>+static inline void call_function_init(void) { }
> 
> static inline int
> smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
>diff --git a/init/main.c b/init/main.c
>index 4a9479e..12821d1 100644
>--- a/init/main.c
>+++ b/init/main.c
>@@ -539,6 +539,7 @@ asmlinkage void __init start_kernel(void)
> 	timekeeping_init();
> 	time_init();
> 	profile_init();
>+	call_function_init();
> 	if (!irqs_disabled())
> 		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
> 				 "enabled early\n");
>diff --git a/kernel/smp.c b/kernel/smp.c
>index 73a1951..fb67dfa 100644
>--- a/kernel/smp.c
>+++ b/kernel/smp.c
>@@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata 
>hotplug_cfd_notifier = {
> 	.notifier_call		= hotplug_cfd,
> };
> 
>-static int __cpuinit init_call_single_data(void)
>+void __init call_function_init(void)
> {
> 	void *cpu = (void *)(long)smp_processor_id();
> 	int i;
>@@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
> 
> 	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
> 	register_cpu_notifier(&hotplug_cfd_notifier);
>-
>-	return 0;
> }
>-early_initcall(init_call_single_data);
> 
> /*
>  * csd_lock/csd_unlock used to serialize access to per-cpu csd resources

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Ingo Molnar]

* Takao Indoh <indou.takao@jp.fujitsu.com> wrote:

> Just a reminder...
> 
> Thanks for acks, but I'm still waiting for inclusion.
> I tested 3.0.0-rc3 and kdump still failed due to pending IPI
> from 1st kernel. Need this patch to fix it.

For any future patch that has a review discussion (like this one) 
please collect Acks and resend the patch with the acks included once 
the discussion results in a final patch, otherwise maintainers might 
skip the patch as "still being reviewed".

I've collected the acks here and started testing your patch.

Thanks,

	Ingo

Re: [PATCH v2] generic-ipi: Initialize call_single_queue before enabling interrupt

[Takao Indoh]

On Fri, 17 Jun 2011 10:19:11 +0200, Ingo Molnar wrote:

>
>* Takao Indoh <indou.takao@jp.fujitsu.com> wrote:
>
>> Just a reminder...
>> 
>> Thanks for acks, but I'm still waiting for inclusion.
>> I tested 3.0.0-rc3 and kdump still failed due to pending IPI
>> from 1st kernel. Need this patch to fix it.
>
>For any future patch that has a review discussion (like this one) 
>please collect Acks and resend the patch with the acks included once 
>the discussion results in a final patch, otherwise maintainers might 
>skip the patch as "still being reviewed".
>
>I've collected the acks here and started testing your patch.

Ok, understood. Thanks for your advice.

Thanks,
Takao Indoh


>
>Thanks,
>
>	Ingo

[tip:sched/urgent] generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts

[tip-bot for Takao Indoh]

Commit-ID:  d8ad7d1123a960cc9f276bd499f9325c6f5e1bd1
Gitweb:     http://git.kernel.org/tip/d8ad7d1123a960cc9f276bd499f9325c6f5e1bd1
Author:     Takao Indoh <indou.takao@jp.fujitsu.com>
AuthorDate: Tue, 29 Mar 2011 12:35:04 -0400
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 17 Jun 2011 10:17:12 +0200

generic-ipi: Fix kexec boot crash by initializing call_single_queue before enabling interrupts

There is a problem that kdump(2nd kernel) sometimes hangs up due
to a pending IPI from 1st kernel. Kernel panic occurs because IPI
comes before call_single_queue is initialized.

To fix the crash, rename init_call_single_data() to call_function_init()
and call it in start_kernel() so that call_single_queue can be
initialized before enabling interrupts.

The details of the crash are:

 (1) 2nd kernel boots up

 (2) A pending IPI from 1st kernel comes when irqs are first enabled
     in start_kernel().

 (3) Kernel tries to handle the interrupt, but call_single_queue
     is not initialized yet at this point. As a result, in the
     generic_smp_call_function_single_interrupt(), NULL pointer
     dereference occurs when list_replace_init() tries to access
     &q->list.next.

Therefore this patch changes the name of init_call_single_data()
to call_function_init() and calls it before local_irq_enable()
in start_kernel().

Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Milton Miller <miltonm@bga.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/D6CBEE2F420741indou.takao@jp.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 include/linux/smp.h |    5 ++++-
 init/main.c         |    1 +
 kernel/smp.c        |    5 +----
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 7ad824d..8cc38d3 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -85,12 +85,15 @@ int smp_call_function_any(const struct cpumask *mask,
  * Generic and arch helpers
  */
 #ifdef CONFIG_USE_GENERIC_SMP_HELPERS
+void __init call_function_init(void);
 void generic_smp_call_function_single_interrupt(void);
 void generic_smp_call_function_interrupt(void);
 void ipi_call_lock(void);
 void ipi_call_unlock(void);
 void ipi_call_lock_irq(void);
 void ipi_call_unlock_irq(void);
+#else
+static inline void call_function_init(void) { }
 #endif
 
 /*
@@ -134,7 +137,7 @@ static inline void smp_send_reschedule(int cpu) { }
 #define smp_prepare_boot_cpu()			do {} while (0)
 #define smp_call_function_many(mask, func, info, wait) \
 			(up_smp_call_function(func, info))
-static inline void init_call_single_data(void) { }
+static inline void call_function_init(void) { }
 
 static inline int
 smp_call_function_any(const struct cpumask *mask, smp_call_func_t func,
diff --git a/init/main.c b/init/main.c
index cafba67..d7211fa 100644
--- a/init/main.c
+++ b/init/main.c
@@ -542,6 +542,7 @@ asmlinkage void __init start_kernel(void)
 	timekeeping_init();
 	time_init();
 	profile_init();
+	call_function_init();
 	if (!irqs_disabled())
 		printk(KERN_CRIT "start_kernel(): bug: interrupts were "
 				 "enabled early\n");
diff --git a/kernel/smp.c b/kernel/smp.c
index 73a1951..fb67dfa 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -74,7 +74,7 @@ static struct notifier_block __cpuinitdata hotplug_cfd_notifier = {
 	.notifier_call		= hotplug_cfd,
 };
 
-static int __cpuinit init_call_single_data(void)
+void __init call_function_init(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
 	int i;
@@ -88,10 +88,7 @@ static int __cpuinit init_call_single_data(void)
 
 	hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
 	register_cpu_notifier(&hotplug_cfd_notifier);
-
-	return 0;
 }
-early_initcall(init_call_single_data);
 
 /*
  * csd_lock/csd_unlock used to serialize access to per-cpu csd resources