runtime: track time or counts goroutine entered runtime #6809
Description
For debugging goroutine leaks, it would be nice if the runtime could tell me how long each goroutine had been stuck in its current state. e.g. a goroutine blocked on a lock or channel send/recv for hours is probably busted. Could that timestamp be kept per-G? It's not much more memory. The time need not be perfectly accurate, either (if getting time every entry into runtime is viewed as too expensive), since the point I at least care about is just seeing very old things. Alternatively, all of this could be done in my own program (polling every ~30 seconds) if I had a per-G unique value that changed whenever the goroutine state changed. A per-G counter would be enough, incremented every entry to the runtime.