[Linux-cluster] suitability for embedded applications

[Patrick Caulfield]

Christopher Friedt wrote:
> Hi,
> 
> I'm currently writing my own light-weight DLM and my manager says that
> its taking too long and I should look at using something already out there.
> 
> I need to lock a shared resource in a building with nodes on the same
> LAN - specifically I'm locking a radio frequency (truly a shared
> resource, in every sense of the word).
> 
> Network latency can be assumed to be very small.
> 
> Only one node is allowed to transmit / receive on the radio frequency at
> one time.
> 
> The article on KernelTrap[1] pointed me here, and I just wanted to ask a
> few questions.
> 
> - is DLM suitable for embedded systems ?
> - what are the major changes / additions, etc to the linux kernel ?
> - does it patch to the latest linux kernel?
> - does it patch to the 2.4 kernels?
> - are any user-space tools necessary?

You'll need libdlm, which is included in the cluster suite CVS or
tarballs at http://sourceware.org/cluster/

It uses a device node interface to communication with the DLM in the kernel.

> - how does an application interface to DLM ? (device node? etc)

There is a VMS-Style call interface that provides full access to all of
the facilities. there's also a simpler on for basic lock/unlock
requests. That is provided by libdlm.

Documentation here:
http://people.redhat.com/pcaulfie/docs/rhdlmbook.pdf


> - to the best of your knowlege, would DLM be suitable for the scenario I
> described above?

Hard to tell to be perfectly honest. The major user of the DLM is GFS, a
cluster filesystem though it is designed to be a generic DLM.

Patrick