What is perimeter locking notably in the context of embedded systems?

Question

I keep hearing "perimeter locking" along with other topics such as "race conditions, IPC .." - what does "perimeter locking" mean? any pointers or links will be helpful too. I see it being referred to under "Job Requirements" such as " understanding concepts of DMA engines, interrupts, timers, memory virtualization, race conditions, and perimeter locking..." I recognize others but not "perimeter locking".
Thanks

Answer 1

Probably things like "do not leave a JTAG/ISP connector accessible". For a regular PC it would clearly also include the firewire port which can be (ab)used to do interesting things like accessing the PC's memory without running special software on it.

Answer 2

This is one instance where I'm aware of 'perimeter lock' usage in embedded systems software context.

Assume an embedded system software module which exposes multiple APIs. By design, the module require each of those API to be mutually exclusive in execution. This is generally achieved by using a 'mutex' to guard the entry-exit of the APIs. This mutex is referred as 'perimeter lock'.