Dynamically Linked Libraries

[wireties]

Originally Posted by AustinSchuh

We actually achieve the same thing through a different mechanism.

Our robot code is split up into a bunch of processes (each is a separate binary). There is 1 process which has WPILib built into it and interfaces to the hardware. The other processes have our control loops, joystick code, autonomous mode, etc. They all communicate via a shared memory mechanism we designed. The really cool part is that this lets us re-start the various modules and replace them without taking the rest of the code down or restart it. We've been able to do things like deploy new joystick code while the driver was driving.

Our code is structured in much the same way but is multi-threaded and uses pipes for communications (mostly because we ported from VxWorks message queues).

How did you implement the shared memory? We noticed that POSIX message queues are not in the kernel. Is the POSIX shared memory API supported? Or maybe SystemV style shared memory? Or did you do something custom?

TIA

[AustinSchuh]

Originally Posted by wireties

How did you implement the shared memory? We noticed that POSIX message queues are not in the kernel. Is the POSIX shared memory API supported? Or maybe SystemV style shared memory? Or did you do something custom?

Essentially SystemV shared memory, though we just use the mmap call directly to map a file from /dev/shm/ in. We then built up message queues with mutexes, condition variables, etc in that memory and use those. That lets you use priority inversion safe mutexes, which is good.

[Hsifeulbhsifder]

Just putting this out there, thank you all for all your help. I have successful dynamic loading of code and am able to make changes to the program while the robot is active.