Re: WARNING: at kernel/smp.c:385 smp_call_function_many

[Sasha Levin <sasha.levin@oracle.com>]

On 04/18/2013 08:29 PM, Sasha Levin wrote:
> Hi Liu,
> 
> On 04/18/2013 08:10 PM, Liu, Chuansheng wrote:
>>> It seems that with commit "smp: Give WARN()ing when calling
>>>> smp_call_function_many()/single() in serving irq" I'm getting a bunch of these:
>> This patch gives the warning even when the smp_call_function_many() is called in softirq context,
>> because it will bring the possible deadlock cases, the example is below:
>> CPUA                            CPUB
>>                                 spin_lock(&spinlock)
>>                                 Any irq coming, call the irq handler
>>                                 irq_exit()
>> spin_lock_irq(&spinlock)
>> <== Blocking here due to
>> CPUB hold it
>>                                   __do_softirq()
>>                                     run_timer_softirq()
>>                                       timer_cb()
>>                                         call smp_call_function_many()
>>                                           send IPI interrupt to CPUA
>>                                             wait_csd()
>>
>> Then both CPUA and CPUB will be deadlocked here.
> 
> Right.
> 
> So commit f55a6faa3 ("hrtimer: Provide clock_was_set_delayed()") followed by one
> of the commits that used clock_was_set_delayed() may trigger the deadlock you've
> described. (cc John Stultz...)

Ping?


Thanks,
Sasha