[llvm] [LLVM] Remove the requirement for named pipe in jobserver (PR #169154)

[Yaxun Liu via llvm-commits]

yxsamliu wrote:

This change looks good functionally, but I think it leaves some confusing naming and comments behind.

Previously, JobserverConfig::PosixFifo was tightly coupled to a real POSIX FIFO (we enforced S_ISFIFO), so the fifo naming and comments in this code matched the actual kernel object. Now that we intentionally accept any endpoint that implements the jobserver token protocol (including FUSE files or CUSE character devices), the FIFO terminology becomes misleading: it's really 'FIFO-compatible endpoint as described by fifo: in MAKEFLAGS', not necessarily a kernel FIFO.

It would be clearer to future readers if we adjusted the naming/comments in a follow-up:

- In Unix/Jobserver.inc:
  - The constructor comment around L40-L44 ("For FIFO-based jobservers, it opens the named pipe") and the comment on release() ("For FIFO-based jobservers, the write FD might not be open yet") should be reworded to something like 'FIFO-style' or 'path-based jobservers'.
  - The member FifoPath and related debug messages ("opening FIFO", "Opened FIFO as new WriteFD") could be renamed to something like EndpointPath or JobserverPath.

- In Jobserver.cpp:
  - The FifoPath local and JobserverConfig::FifoPath member share the same assumption and may deserve a more generic name or an updated comment explaining that fifo: is a protocol tag, not a strict type guarantee.


https://github.com/llvm/llvm-project/pull/169154