For starters, it doesn’t run on the channel subsystem, but uses the CPU for it. Also, channel programs (the IBM ones) can do a lot of stuff - IBM’s ISAM uses self-modifying channel programs. These channels can’t be that flexible because they run within the kernel and being too flexible would be a security risk.
> For starters, it doesn’t run on the channel subsystem, but uses the CPU for it.
Low/mid range mainframes don't really make sense anymore, but channel programs did run on the main CPU on quite a few low/mid range mainframe systems.
> Also, channel programs (the IBM ones) can do a lot of stuff - IBM’s ISAM uses self-modifying channel programs. These channels can’t be that flexible because they run within the kernel and being too flexible would be a security risk.
There's no reason this couldn't do that either as long as it's run in a preemptable context (which I'm pretty sure is the case from looking at the example program). Schemes like eBPF mainly control code flow in pursuit of the goal of running in non preemptable contexts like interrupts.
