Imagine 1000 pipes, each of which has a goroutine calling write() and another calling read(). If you schedule all of the writers and none of the readers (or vice versa) you'll get a deadlock.
AFAIK when a goroutine "calls write" (on a channel or on a socket, stream, mutex etc).. and the write "is blocked" it yields the execution and the scheduler can activate something else.. which can be a reader goroutine (after all the writers are blocked for example). So there's no deadlock as long as you have at least one reader for any writer.
That requires the underlying syscall to support an async or non blocking mode though. Disk io or stat doesn't on linux for example. The usual alternative is some sort of background pool for blocking tasks (which adds non trivial overhead), or, where supported by the OS, scheduler activation.
Sorry, I also expected those things that can be translated into non-blocking calls with select-ish apis for readiness to be translated as well -- because it's the right thing to do in this type of environment.
To be more specific, most socket calls should be async + selectish, but file system calls would likely be done as synchronous, because async doesn't generally work for that -- anyway limiting the number of outstanding file I/O requests tends to help throughput.
stat() cannot (on platforms I am familiar with) be performed in a selectish/nonblocking way. That call can block forever. Local filesystem access in general is still not async-capable in very important ways.
Yes, filesystem calls are going to block -- but putting that into a limited threadpool shouldn't deadlock your system -- you can't do a blocking read on a file, waiting for it to be filled by another thread (unless/until you start playing with FUSE, I guess.
