Re: [PATCH RT] nvdimm: make lane acquirement RT aware

[Sebastian Andrzej Siewior]

On 2019-03-18 01:41:10 [+0000], Liu, Yongxin wrote:
> 
> Consider the recursive call to nd_region_acquire_lane() in the following situation.
> Will there be a dead lock?
> 
> 
>     Thread A                    Thread B
>        |                           |
>        |                           |
>      CPU 1                       CPU 2
>        |                           |
>        |                           |
>  get lock for Lane 1         get lock for Lane 2
>        |                           |
>        |                           |
>  migrate to CPU 2            migrate to CPU 1
>        |                           |
>        |                           |
>  wait lock for Lane 2        wait lock for Lane 1 
>        |                           |
>        |                           |
>        _____________________________
>                    |
>                 dead lock ?

Bummer. That would dead lock indeed.
Is it easily possible to recognize the recursive case? 

> 
> Thanks,
> Yognxin

Sebastian