Revert "Preserve select(2) semantics when the other end of the pipe is gone".

The logic to emulate the current poll/select behavior is better implemented
at the syscall layer and not in the kqueue backend.

Discussed with deraadt@, ok anton@

diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index fa85571..1317ea4 100644 (file)
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sys_pipe.c,v 1.127 2021/10/22 05:00:26 anton Exp $    */
+/*     $OpenBSD: sys_pipe.c,v 1.128 2021/10/22 15:16:50 mpi Exp $      */
 
 /*
  * Copyright (c) 1996 John S. Dyson
@@ -890,27 +890,16 @@ pipe_kqfilter(struct file *fp, struct knote *kn)
                kn->kn_hook = rpipe;
                klist_insert_locked(&rpipe->pipe_sel.si_note, kn);
                break;
-       case EVFILT_WRITE: {
-               struct pipe *kpipe = wpipe;
-
+       case EVFILT_WRITE:
                if (wpipe == NULL) {
                        /* other end of pipe has been closed */
-                       if (kn->kn_flags & __EV_POLL) {
-                               /*
-                                * select(2) semantics requires the pipe to
-                                * become ready only to deliver EPIPE.
-                                */
-                               kpipe = rpipe;
-                       } else {
-                               error = EPIPE;
-                               break;
-                       }
+                       error = EPIPE;
+                       break;
                }
                kn->kn_fop = &pipe_wfiltops;
-               kn->kn_hook = kpipe;
-               klist_insert_locked(&kpipe->pipe_sel.si_note, kn);
+               kn->kn_hook = wpipe;
+               klist_insert_locked(&wpipe->pipe_sel.si_note, kn);
                break;
-       }
        default:
                error = EINVAL;
        }