kern/60789: read on fifo without writer may block

["campbell+netbsd%mumble.net@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60789
>Category:       kern
>Synopsis:       read on fifo without writer may block
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Sep 25 15:05:00 +0000 2026
>Originator:     Taylor R Campbell
>Release:        current, 11, 10, ...
>Organization:
End-of-fifo Blocks and Pipes LLC
>Environment:
>Description:

	POSIX sez:

> When attempting to read from an empty pipe or FIFO:
> 
> - If no process has the pipe open for writing, read() shall return 0
>   to indicate end-of-file.

	And that sometimes happens.  But sometimes, on a named pipe,
	read() blocks instead.

>How-To-Repeat:

	barge into a GNU coreutils bug discussion certain that NetBSD
	is right _this_ time and walk away with tail between legs

>Fix:

	Yes, please!