CVS commit: src

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

Module Name:    src
Committed By:   riastradh
Date:           Sat Oct  3 16:26:51 UTC 2026

Modified Files:
        src/sys/kern: sys_pipe.c
        src/tests/lib/libc/sys: t_poll.c t_sigio.c

Log Message:
pipe(2): Restructure select/poll/kqueue records.

1. When a thread is waiting on an endpoint of a pipe, have it wait on
   _that endpoint_ (i.e., cv_wait or selrecord), not on the other
   endpoint sometimes depending on the direction of the I/O.

2. Make poll(2) on the writer side of a pipe wake with POLLERR when
   the reader side is closed, because write would return immediately,
   and fail with EPIPE/SIGPIPE.  See also:

   https://mail-index.NetBSD.org/tech-kern/2026/09/21/msg031255.html

   (In contrast, for the other way around, when the writer side of a
   pipe is closed, poll(2) on the reader is already defined to wake
   with POLLHUP, and while read would return immediately, it will not
   _fail_; it will simply report EOF, so there is no justification
   for POLLERR in that direction.)

3. For EVFILT_READ, require the reader side of a pipe; likewise, for
   EVFILT_WRITE, require the writer side of a pipe.  That this wasn't
   enforced before was an accident, as far as I can tell, and made
   the kevent paths very confusing about which side of the pipe is
   which.

PR kern/59056: poll POLLHUP bugs


To generate a diff of this commit:
cvs rdiff -u -r1.173 -r1.174 src/sys/kern/sys_pipe.c
cvs rdiff -u -r1.18 -r1.19 src/tests/lib/libc/sys/t_poll.c
cvs rdiff -u -r1.6 -r1.7 src/tests/lib/libc/sys/t_sigio.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.