use named pipe when creating new jobserver

[NobodyXu]

Thanks, my proposed solution is to change rust-lang/jobserver to use a named pipe instead of an annoymous one.

The named pipe is passed down by its path in filesystem and opening it using O_NONBLOCK doesn't affect others.

We can also retain backwards compatibility by keeping the jobserver fds inheritable and keeping them in the environment variable.

E.g. MAKEFLAGS='--jobserver-auth=fifo:/path/to/fifo --jobserver-fds=3,5'

Originally posted by @NobodyXu in #13476 (comment)

[NobodyXu]

cc @weihanglo since you also interacted with the issue in cargo.

[weihanglo]

Thanks for the report.

This is somehow blocked on rust-lang/jobserver-rs#47 or something need to be done there I feel like. How can Cargo help the situation, or is this just a tracking issue of that?

[NobodyXu]

This is somehow blocked on rust-lang/jobserver-rs#47 or something need to be done there I feel like.

Hmmm is that for previous cargo release which uses an old jobserver version?

I thought that latest version of jobserver can handle it just well?

How can Cargo help the situation, or is this just a tracking issue of that?

I will open a PR in next few days, and hopefully we can cut a new patch release of cargo to use the latest jobserver release.

[weihanglo]

I thought that latest version of jobserver can handle it just well?

🤔… Unless I missed something important, there seems no way for Cargo to create a fifo jobserver via jobserver crate.

[NobodyXu]

Unless I missed something important, there seems no way for Cargo to create a fifo jobserver via jobserver crate.

That's what I'm proposing: change jobserver::Client::new to create a fifo instead of pipe by default and retain backwards compatibility by making it inheritable with env MAKEFLAGS='--jobserver-auth=fifo:/path/to/fifo --jobserver-fds=3,5'.

AFAIK --jobserver-auth is introduced when fifo is first supported in make.

[NobodyXu]

I was meant to create this on rust-lang/iobserver 😂

[NobodyXu]

Unfortunately, --jobserver-auth is introduced in 4.2, but fifo jobserver and --jobserver-style is introduced in make 4.4

This means that if we use fifo we would break backwards compatibility, so closing this for now.