-----Original Message-----
From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-
owner@vger.kernel.org] On Behalf Of Sebastian Andrzej Siewior
Sent: Monday, March 18, 2019 19:40
To: Liu, Yongxin
Cc: linux-kernel@vger.kernel.org; linux-rt-users@vger.kernel.org;
tglx@linutronix.de; rostedt@goodmis.org; dan.j.williams@intel.com;
pagupta@redhat.com; Gortmaker, Paul; linux-nvdimm@lists.01.org
Subject: Re: [PATCH RT] nvdimm: make lane acquirement RT aware

On 2019-03-18 01:41:10 [+0000], Liu, Yongxin wrote:

quoted

Consider the recursive call to nd_region_acquire_lane() in the

following situation.

quoted

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?

Not easily. I don't have test case for recursive call. 
For now, just code analysis.


Yongxin

quoted

Thanks,
Yognxin

Sebastian