PR/59578 CVS commit: src/tests/lib/libc/sys

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

The following reply was made to PR kern/59578; it has been noted by GNATS.

From: "Taylor R Campbell" <riastradh%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/59578 CVS commit: src/tests/lib/libc/sys
Date: Tue, 22 Sep 2026 13:32:24 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Tue Sep 22 13:32:24 UTC 2026
 
 Modified Files:
 	src/tests/lib/libc/sys: t_mkfifo.c
 
 Log Message:
 t_mkfifo: Add test for PR kern/59578.
 
 The problem is:
 
 thread A                        thread B
 --------                        --------
 enter open("fifo", O_WRONLY)
 -> fi_writers++
 -> sleep since fi_readers == 0
                                 enter open("fifo", O_RDONLY)
                                 -> fi_readers++
                                 -> return since fi_writers > 0
                                 open succeeds with fd
                                 enter close(fd)
                                 -> fi_readers--
                                 close succeeds
 *SIGALRM*
 -> fi_writers--
 open fails with EINTR
 
 At this point, a reader open() has succeeded with no corresponding
 writer open() success, and if the writer retries, it will hang
 because fi_readers is back to zero.  Instead, when the reader open()
 succeeds, it should cause the writer open() to succeed as well (and
 handle the signal afterward).
 
 Same problem occurs in with the reader/writer roles reversed.
 
 PR kern/59578: open() hangs indefinitely on FIFO with frequent signal
 interruption
 
 Related bugs:
 
 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=203162
 https://bugs.python.org/issue25122
 https://github.com/python/cpython/issues/137397
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.4 -r1.5 src/tests/lib/libc/sys/t_mkfifo.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.