Re: [PATCH] mips: irq: add statckoverflow detection

[David Daney <ddaney@caviumnetworks.com>]

On 08/25/2010 06:12 PM, Adam Jiang wrote:
> 2010/8/26 David Daney<ddaney@caviumnetworks.com>:
>> It looks like this patch only checks when processing an interrupt, which
>> doesn't seem like it would give much coverage.
>
> Yes, it is. This is only for detection on the situation which may be
> caused by nested interruption. No more coverage to any other cases.
> Because to do that is much difficult and unpredicted.
>

Well, since the default is to run interrupt handlers with interrupts 
disabled, it seems like it is of little use as you will almost never see 
nested interrupts.

A solution that shows overflow in all situations would be of more use. 
Something that could use GCC's -stack-check or related machinery might 
be interesting.

David Daney


> I will revise the bad code style Sergei blamed.
>
> /Adam
>
>>
>> Am I missing something?
>>
>> David Daney
>>
>>
>> On 08/20/2010 11:31 PM, jiang.adam@gmail.com wrote:
>>>
>>> From: Adam Jiang<jiang.adam@gmail.com>
>>>
>>> Add stackoverflow detection to mips arch
>>>
>>> Signed-off-by: Adam Jiang<jiang.adam@gmail.com>
>>> ---
>>>   arch/mips/Kconfig.debug |    7 +++++++
>>>   arch/mips/kernel/irq.c  |   19 +++++++++++++++++++
>>>   2 files changed, 26 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
>>> index 43dc279..f1a00a2 100644
>>> --- a/arch/mips/Kconfig.debug
>>> +++ b/arch/mips/Kconfig.debug
>>> @@ -67,6 +67,13 @@ config CMDLINE_OVERRIDE
>>>
>>>           Normally, you will choose 'N' here.
>>>
>>> +config DEBUG_STACKOVERFLOW
>>> +       bool "Check for stack overflows"
>>> +       depends on DEBUG_KERNEL
>>> +       help
>>> +         This option will cause messages to be printed if free stack
>>> space
>>> +         drops below a certain limit.
>>> +
>>>   config DEBUG_STACK_USAGE
>>>         bool "Enable stack utilization instrumentation"
>>>         depends on DEBUG_KERNEL
>>> diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
>>> index c6345f5..6334037 100644
>>> --- a/arch/mips/kernel/irq.c
>>> +++ b/arch/mips/kernel/irq.c
>>> @@ -151,6 +151,22 @@ void __init init_IRQ(void)
>>>   #endif
>>>   }
>>>
>>> +static inline void check_stack_overflow(void)
>>> +{
>>> +#ifdef CONFIG_DEBUG_STACKOVERFLOW
>>> +       long sp;
>>> +
>>> +       asm volatile("move %0, $sp" : "=r" (sp));
>>> +       sp = sp&    (THREAD_SIZE-1);
>>> +
>>> +       /* check for stack overflow: is there less then 2KB free? */
>>> +       if (unlikely(sp<    (sizeof(struct thread_info) + 2048))) {
>>> +               printk("do_IRQ: stack overflow: %ld\n",
>>> +                      sp - sizeof(struct thread_info));
>>> +               dump_stack();
>>> +       }
>>> +#endif
>>> +}
>>>   /*
>>>    * do_IRQ handles all normal device IRQ's (the special
>>>    * SMP cross-CPU interrupts have their own specific
>>> @@ -159,6 +175,9 @@ void __init init_IRQ(void)
>>>   void __irq_entry do_IRQ(unsigned int irq)
>>>   {
>>>         irq_enter();
>>> +
>>> +       check_stack_overflow();
>>> +
>>>         __DO_IRQ_SMTC_HOOK(irq);
>>>         generic_handle_irq(irq);
>>>         irq_exit();
>>
>>