max_blocking_threads documentation should perhaps indicate that Tokio internally uses those too

[krallin]

Version

1.25.0

Platform

Windows, any version

Description

As written, the documentation for max_blocking_threads suggests it's only used for

This probably warrants a small disclaimer that setting this low-ish may be a good idea. In particular, on Windows, reading a pipe is a blocking read and will take away a blocking thread forever.

If you set max_blocking_threads to a low value (e.g. in our case, in a test, we were setting it to 2), you can easily find yourself in a situation where spawn_blocking just hangs forever, because all your blocking threads are waiting on a pair of idle pipes (stdout and stderr of a child process, in our case), which might be rather unexpected!

[Darksonn]

Sure, adding that makes sense to me.