[src/trunk]: src Fix reporting EOF via kevent and add a test case

[mgorny <mgorny%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/871476ea0a8f
branches:  trunk
changeset: 996970:871476ea0a8f
user:      mgorny <mgorny%NetBSD.org@localhost>
date:      Fri Feb 15 18:57:15 2019 +0000

description:
Fix reporting EOF via kevent and add a test case

Fix the kernel pty driver to report closed slave via master's kevent
EVFILT_READ.  This behavior matches the behavior for pipes, is
consistent with how FreeBSD implements it and is relied upon by LLDB's
main loop implementation.

Includes feedback by kre and kamil (from tech-kern), commit approved
by kamil.

diffstat:

 sys/kern/tty_pty.c                  |   8 ++++-
 tests/kernel/kqueue/read/t_ttypty.c |  47 +++++++++++++++++++++++++++++++++---
 2 files changed, 49 insertions(+), 6 deletions(-)

diffs (106 lines):

diff -r 22cfe48d7ce0 -r 871476ea0a8f sys/kern/tty_pty.c
--- a/sys/kern/tty_pty.c        Fri Feb 15 16:42:27 2019 +0000
+++ b/sys/kern/tty_pty.c        Fri Feb 15 18:57:15 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: tty_pty.c,v 1.144 2018/09/03 16:29:35 riastradh Exp $  */
+/*     $NetBSD: tty_pty.c,v 1.145 2019/02/15 18:57:15 mgorny Exp $     */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: tty_pty.c,v 1.144 2018/09/03 16:29:35 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: tty_pty.c,v 1.145 2019/02/15 18:57:15 mgorny Exp $");
 
 #include "opt_ptm.h"
 
@@ -938,6 +938,10 @@
                    ((pti->pt_flags & PF_UCNTL) && pti->pt_ucntl))
                        kn->kn_data++;
        }
+       if (!ISSET(tp->t_state, TS_CARR_ON)) {
+               kn->kn_flags |= EV_EOF;
+               canread = 1;
+       }
 
        if ((hint & NOTE_SUBMIT) == 0) {
                mutex_spin_exit(&tty_lock);
diff -r 22cfe48d7ce0 -r 871476ea0a8f tests/kernel/kqueue/read/t_ttypty.c
--- a/tests/kernel/kqueue/read/t_ttypty.c       Fri Feb 15 16:42:27 2019 +0000
+++ b/tests/kernel/kqueue/read/t_ttypty.c       Fri Feb 15 18:57:15 2019 +0000
@@ -1,7 +1,7 @@
-/* $NetBSD: t_ttypty.c,v 1.2 2017/01/13 21:30:41 christos Exp $ */
+/* $NetBSD: t_ttypty.c,v 1.3 2019/02/15 18:57:15 mgorny Exp $ */
 
 /*-
- * Copyright (c) 2002, 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2002, 2008, 2019 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -30,11 +30,12 @@
  */
 
 #include <sys/cdefs.h>
-__COPYRIGHT("@(#) Copyright (c) 2008\
+__COPYRIGHT("@(#) Copyright (c) 2008, 2019\
  The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: t_ttypty.c,v 1.2 2017/01/13 21:30:41 christos Exp $");
+__RCSID("$NetBSD: t_ttypty.c,v 1.3 2019/02/15 18:57:15 mgorny Exp $");
 
 #include <sys/event.h>
+#include <sys/time.h>
 #include <sys/wait.h>
 
 #include <poll.h>
@@ -135,10 +136,48 @@
        h_check(false);
 }
 
+ATF_TC(closed_slave);
+ATF_TC_HEAD(closed_slave, tc)
+{
+       atf_tc_set_md_var(tc, "descr",
+               "Checks EVFILT_READ reporting for slave tty being closed");
+}
+ATF_TC_BODY(closed_slave, tc)
+{
+       char slavetty[1024];
+       struct kevent event[1];
+       int amaster, aslave;
+       int kq, n;
+       struct timespec timeout = {5, 0};
+
+       RL(openpty(&amaster, &aslave, slavetty, NULL, NULL));
+
+       (void)printf("tty: openpty master %d slave %d tty '%s'\n",
+               amaster, aslave, slavetty);
+
+       RL(kq = kqueue());
+
+       EV_SET(&event[0], amaster, EVFILT_READ, EV_ADD|EV_ENABLE, 0, 0, 0);
+       RL(kevent(kq, event, 1, NULL, 0, NULL));
+
+       RL(close(aslave));
+
+       RL(n = kevent(kq, NULL, 0, event, 1, &timeout));
+
+       (void)printf("kevent num %d filt %d flags: %#x, fflags: %#x, "
+           "data: %" PRId64 "\n", n, event[0].filter, event[0].flags,
+           event[0].fflags, event[0].data);
+
+       ATF_REQUIRE_EQ(n, 1);
+       ATF_REQUIRE_EQ(event[0].filter, EVFILT_READ);
+       ATF_REQUIRE_EQ(event[0].flags & EV_EOF, EV_EOF);
+}
+
 ATF_TP_ADD_TCS(tp)
 {
        ATF_TP_ADD_TC(tp, master);
        ATF_TP_ADD_TC(tp, slave);
+       ATF_TP_ADD_TC(tp, closed_slave);
 
        return atf_no_error();
 }