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1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3 * Test that poll handlers are not re-entrant in nested aio_poll()
4 *
5 * Copyright Red Hat
6 *
7 * Poll handlers are usually level-triggered. That means they continue firing
8 * until the condition is reset (e.g. a virtqueue becomes empty). If a poll
9 * handler calls nested aio_poll() before the condition is reset, then infinite
10 * recursion occurs.
11 *
12 * aio_poll() is supposed to prevent this by disabling poll handlers in nested
13 * aio_poll() calls. This test case checks that this is indeed what happens.
14 */
15 #include "qemu/osdep.h"
16 #include "qemu/aio.h"
17 #include "qapi/error.h"
18 #include "util/aio-posix.h"
19
20 typedef struct {
21 AioContext *ctx;
22
23 /* This is the EventNotifier that drives the test */
24 EventNotifier poll_notifier;
25
26 /* This EventNotifier is only used to wake aio_poll() */
27 EventNotifier dummy_notifier;
28
29 bool nested;
30 } TestData;
31
32 static void io_read(EventNotifier *notifier)
33 {
34 event_notifier_test_and_clear(notifier);
35 }
36
37 static bool io_poll_true(void *opaque)
38 {
39 return true;
40 }
41
42 static bool io_poll_false(void *opaque)
43 {
44 return false;
45 }
46
47 static void io_poll_ready(EventNotifier *notifier)
48 {
49 TestData *td = container_of(notifier, TestData, poll_notifier);
50
51 g_assert(!td->nested);
52 td->nested = true;
53
54 /* Wake the following nested aio_poll() call */
55 event_notifier_set(&td->dummy_notifier);
56
57 /* This nested event loop must not call io_poll()/io_poll_ready() */
58 g_assert(aio_poll(td->ctx, true));
59
60 td->nested = false;
61 }
62
63 /* dummy_notifier never triggers */
64 static void io_poll_never_ready(EventNotifier *notifier)
65 {
66 g_assert_not_reached();
67 }
68
69 static void test(void)
70 {
71 TestData td = {
72 .ctx = aio_context_new(&error_abort),
73 };
74
75 if (td.ctx->fdmon_ops != &fdmon_poll_ops) {
76 /* This test is tied to fdmon-poll.c */
77 g_test_skip("fdmon_poll_ops not in use");
78 return;
79 }
80
81 qemu_set_current_aio_context(td.ctx);
82
83 /* Enable polling */
84 aio_context_set_poll_params(td.ctx, 1000000, 2, 2, 3, &error_abort);
85
86 /* Make the event notifier active (set) right away */
87 event_notifier_init(&td.poll_notifier, 1);
88 aio_set_event_notifier(td.ctx, &td.poll_notifier,
89 io_read, io_poll_true, io_poll_ready);
90
91 /* This event notifier will be used later */
92 event_notifier_init(&td.dummy_notifier, 0);
93 aio_set_event_notifier(td.ctx, &td.dummy_notifier,
94 io_read, io_poll_false, io_poll_never_ready);
95
96 /* Consume aio_notify() */
97 g_assert(!aio_poll(td.ctx, false));
98
99 /*
100 * Run the io_read() handler. This has the side-effect of activating
101 * polling in future aio_poll() calls.
102 */
103 g_assert(aio_poll(td.ctx, true));
104
105 /* The second time around the io_poll()/io_poll_ready() handler runs */
106 g_assert(aio_poll(td.ctx, true));
107
108 /* Run io_poll()/io_poll_ready() one more time to show it keeps working */
109 g_assert(aio_poll(td.ctx, true));
110
111 aio_set_event_notifier(td.ctx, &td.dummy_notifier, NULL, NULL, NULL);
112 aio_set_event_notifier(td.ctx, &td.poll_notifier, NULL, NULL, NULL);
113 event_notifier_cleanup(&td.dummy_notifier);
114 event_notifier_cleanup(&td.poll_notifier);
115 aio_context_unref(td.ctx);
116 }
117
118 int main(int argc, char **argv)
119 {
120 g_test_init(&argc, &argv, NULL);
121 g_test_add_func("/nested-aio-poll", test);
122 return g_test_run();
123 }