Add a test for https://reviews.freebsd.org/D31858 (PR 258310)

This test (based on https://github.com/jiixyj/epoll-shim/pull/32#issuecomment-891276654)
fails reproducibly on QEMU with KVM and `-smp 2` prior to D31858 (committed
as 98168a6e6c12dab8f608f6b5f5b0b175d2b87ef0) and passes with the patch applied.

Reviewed By:	kib, imp
Differential Revision: https://reviews.freebsd.org/D31862

2 files changed, 108 insertions, 0 deletions

diff --git a/tests/sys/kqueue/Makefile b/tests/sys/kqueue/Makefile
index 40f892d36fbd..1bf13772f0f2 100644
--- a/tests/sys/kqueue/Makefile
+++ b/tests/sys/kqueue/Makefile
@@ -5,6 +5,8 @@ TESTSRC=	${SRCTOP}/contrib/netbsd-tests/kernel/kqueue
 TESTSDIR=	${TESTSBASE}/sys/kqueue
 BINDIR=		${TESTSDIR}
 
+ATF_TESTS_C+=	kqueue_peek_signal
+
 NETBSD_ATF_TESTS_C=	proc1_test
 # XXX: fails `ke.fflags & NOTE_TRACKERR` invariant
 #NETBSD_ATF_TESTS_C+=	proc2_test
diff --git a/tests/sys/kqueue/kqueue_peek_signal.c b/tests/sys/kqueue/kqueue_peek_signal.c
new file mode 100644
index 000000000000..16dbce68a57c
--- /dev/null
+++ b/tests/sys/kqueue/kqueue_peek_signal.c
@@ -0,0 +1,106 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2021 Jan Kokemüller
+ * Copyright 2021 Alex Richardson <arichardson@FreeBSD.org>
+ *
+ * This work was supported by Innovate UK project 105694, "Digital Security by
+ * Design (DSbD) Technology Platform Prototype".
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <sys/cdefs.h>
+#include <sys/event.h>
+
+#include <atf-c.h>
+#include <errno.h>
+#include <signal.h>
+
+ATF_TC_WITHOUT_HEAD(main);
+
+ATF_TC_BODY(main, tc)
+{
+	int rv;
+
+	sigset_t set;
+	rv = sigemptyset(&set);
+	ATF_REQUIRE_EQ(0, rv);
+	rv = sigaddset(&set, SIGUSR1);
+	ATF_REQUIRE_EQ(0, rv);
+	rv = sigprocmask(SIG_BLOCK, &set, NULL);
+	ATF_REQUIRE_EQ(0, rv);
+
+	int skq = kqueue();
+	ATF_REQUIRE(skq >= 0);
+
+	struct kevent kev;
+	EV_SET(&kev, SIGUSR1, EVFILT_SIGNAL, EV_ADD, 0, 0, 0);
+	rv = kevent(skq, &kev, 1, NULL, 0, NULL);
+	ATF_REQUIRE_EQ(0, rv);
+
+	int kq = kqueue();
+	ATF_REQUIRE(kq >= 0);
+
+	EV_SET(&kev, skq, EVFILT_READ, EV_ADD | EV_CLEAR, 0, 0, 0);
+	rv = kevent(kq, &kev, 1, NULL, 0, NULL);
+	ATF_REQUIRE_EQ(0, rv);
+
+	/*
+	 * It was previously not guaranteed that sending a signal to self would
+	 * be immediately visible in the nested kqueue activation with a zero
+	 * timeout. As of https://reviews.freebsd.org/D31858, the kqueue task
+	 * queue will be processed in this case, so we are guaranteed to see the
+	 * SIGUSR1 here even with a zero timeout. We run the code below in a
+	 * loop to make it more likely that older kernels without the fix fail
+	 * this test.
+	 */
+	for (int i = 0; i < 100; i++) {
+		rv = kill(getpid(), SIGUSR1);
+		ATF_REQUIRE_EQ(0, rv);
+
+		rv = kevent(kq, NULL, 0, &kev, 1, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_EQ_MSG(1, rv,
+		    "Unexpected result %d from kevent() after %d iterations",
+		    rv, i);
+		rv = kevent(kq, NULL, 0, &kev, 1, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_EQ(0, rv);
+
+		rv = kevent(skq, NULL, 0, &kev, 1, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_EQ(1, rv);
+		rv = kevent(skq, NULL, 0, &kev, 1, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_EQ(0, rv);
+
+		siginfo_t siginfo;
+		rv = sigtimedwait(&set, &siginfo, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_EQ(SIGUSR1, rv);
+
+		rv = sigtimedwait(&set, &siginfo, &(struct timespec) { 0, 0 });
+		ATF_REQUIRE_ERRNO(EAGAIN, rv < 0);
+	}
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, main);
+
+	return (atf_no_error());
+}