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

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