bug#48118: 27.1; 28; Only first process receives output with multiple running processes

[Philipp]

> Am 02.05.2021 um 09:23 schrieb Lars Ingebrigtsen <larsi@gnus.org>:
> 
> Daniel Mendler <mail@daniel-mendler.de> writes:
> 
>> This is what we assumed. Emacs could check the second process the next
>> time. This way one may get a slightly more fair behavior.
> 
> Yes, more fairness in how Emacs handles process output would be nice,
> indeed.

An alternative approach would be to randomly shuffle the file descriptors 
before selecting on them.  At least that's what e.g. Go is doing (see the code 
starting from "generate permuted order" in 
https://golang.org/src/runtime/select.go).