tests: add test-fdmon-epoll

Test aio_disable_external(), which switches from fdmon-epoll back to
fdmon-poll. This resulted in an assertion failure that was fixed in the
previous patch.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200915120339.702938-3-stefanha@redhat.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/tests/test-fdmon-epoll.c b/tests/test-fdmon-epoll.c
new file mode 100644
index 0000000000..11fd8a2fa9
--- /dev/null
+++ b/tests/test-fdmon-epoll.c
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * fdmon-epoll tests
+ *
+ * Copyright (c) 2020 Red Hat, Inc.
+ */
+
+#include "qemu/osdep.h"
+#include "block/aio.h"
+#include "qapi/error.h"
+#include "qemu/main-loop.h"
+
+static AioContext *ctx;
+
+static void dummy_fd_handler(EventNotifier *notifier)
+{
+    event_notifier_test_and_clear(notifier);
+}
+
+static void add_event_notifiers(EventNotifier *notifiers, size_t n)
+{
+    for (size_t i = 0; i < n; i++) {
+        event_notifier_init(&notifiers[i], false);
+        aio_set_event_notifier(ctx, &notifiers[i], false,
+                               dummy_fd_handler, NULL);
+    }
+}
+
+static void remove_event_notifiers(EventNotifier *notifiers, size_t n)
+{
+    for (size_t i = 0; i < n; i++) {
+        aio_set_event_notifier(ctx, &notifiers[i], false, NULL, NULL);
+        event_notifier_cleanup(&notifiers[i]);
+    }
+}
+
+/* Check that fd handlers work when external clients are disabled */
+static void test_external_disabled(void)
+{
+    EventNotifier notifiers[100];
+
+    /* fdmon-epoll is only enabled when many fd handlers are registered */
+    add_event_notifiers(notifiers, G_N_ELEMENTS(notifiers));
+
+    event_notifier_set(&notifiers[0]);
+    assert(aio_poll(ctx, true));
+
+    aio_disable_external(ctx);
+    event_notifier_set(&notifiers[0]);
+    assert(aio_poll(ctx, true));
+    aio_enable_external(ctx);
+
+    remove_event_notifiers(notifiers, G_N_ELEMENTS(notifiers));
+}
+
+int main(int argc, char **argv)
+{
+    /*
+     * This code relies on the fact that fdmon-io_uring disables itself when
+     * the glib main loop is in use. The main loop uses fdmon-poll and upgrades
+     * to fdmon-epoll when the number of fds exceeds a threshold.
+     */
+    qemu_init_main_loop(&error_fatal);
+    ctx = qemu_get_aio_context();
+
+    while (g_main_context_iteration(NULL, false)) {
+        /* Do nothing */
+    }
+
+    g_test_init(&argc, &argv, NULL);
+    g_test_add_func("/fdmon-epoll/external-disabled", test_external_disabled);
+    return g_test_run();
+}