Structured concurrency as commonly understood requires children to not outlive parents, recursively. For example, if A spawns B spawns C, then B cancels for C w

Structured concurrency as commonly understood requires children to not outlive parents, recursively. For example, if A spawns B spawns C, then B cancels for C with timeout 30s, then 5s later A cancels B with timeout 5s, then the timeout for C must be effectively reduced by 20s[1]. But the issue here is more basic than timeouts. If we are to use process groups in the example, then B must be a process group leader for C and simultaneously belong to the process group led by A, which is impossible on Unix—that’s what TFA means by “[the] process group mechanism [is] one-level deep”. Close but no cigar. (On the other hand, no reason this can’t be an extension to—I would even say a rationalization of—the process group mechanism. It doesn’t exist right now, though.) [1] https://250bpm.com/blog:71/ https://250bpm.com/blog:71/