Python documentation to Popen states:
Warning Use communicate() rather than .stdin.write, .stdout.read or .stderr.read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process.
Now, I'm trying to figure out how this deadlock can occur and why.
My mental model: subproccess produces something to stdout/err, which is buffered and after buffer is filled, it's flushed to stdout/err of subproccess, which is send through pipe to parent process.
From what documentation states, pipe has it's own buffer and when it's filled or subprocess terminates, it's flushed to to the parent process.
Either way (with pipe buffer or not), I'm not entirely sure how deadlock can occur. Only thing I can think of is some kind of "global" OS pipe buffer processes will be striving for, which sounds strange. Another is that more processes will share same pipe, which should not happen on it's own.
Can someone please explain this?