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 "block/aio.h"
17 #include "qapi/error.h"
18
19 typedef struct {
20 AioContext *ctx;
21
22 /* This is the EventNotifier that drives the test */
23 EventNotifier poll_notifier;
24
25 /* This EventNotifier is only used to wake aio_poll() */
26 EventNotifier dummy_notifier;
27
28 bool nested;
29 } TestData;
30
io_read(EventNotifier * notifier)31 static void io_read(EventNotifier *notifier)
32 {
33 event_notifier_test_and_clear(notifier);
34 }
35
io_poll_true(void * opaque)36 static bool io_poll_true(void *opaque)
37 {
38 return true;
39 }
40
io_poll_false(void * opaque)41 static bool io_poll_false(void *opaque)
42 {
43 return false;
44 }
45
io_poll_ready(EventNotifier * notifier)46 static void io_poll_ready(EventNotifier *notifier)
47 {
48 TestData *td = container_of(notifier, TestData, poll_notifier);
49
50 g_assert(!td->nested);
51 td->nested = true;
52
53 /* Wake the following nested aio_poll() call */
54 event_notifier_set(&td->dummy_notifier);
55
56 /* This nested event loop must not call io_poll()/io_poll_ready() */
57 g_assert(aio_poll(td->ctx, true));
58
59 td->nested = false;
60 }
61
62 /* dummy_notifier never triggers */
io_poll_never_ready(EventNotifier * notifier)63 static void io_poll_never_ready(EventNotifier *notifier)
64 {
65 g_assert_not_reached();
66 }
67
test(void)68 static void test(void)
69 {
70 TestData td = {
71 .ctx = aio_context_new(&error_abort),
72 };
73
74 qemu_set_current_aio_context(td.ctx);
75
76 /* Enable polling */
77 aio_context_set_poll_params(td.ctx, 1000000, 2, 2, &error_abort);
78
79 /*
80 * The GSource is unused but this has the side-effect of changing the fdmon
81 * that AioContext uses.
82 */
83 aio_get_g_source(td.ctx);
84
85 /* Make the event notifier active (set) right away */
86 event_notifier_init(&td.poll_notifier, 1);
87 aio_set_event_notifier(td.ctx, &td.poll_notifier,
88 io_read, io_poll_true, io_poll_ready);
89
90 /* This event notifier will be used later */
91 event_notifier_init(&td.dummy_notifier, 0);
92 aio_set_event_notifier(td.ctx, &td.dummy_notifier,
93 io_read, io_poll_false, io_poll_never_ready);
94
95 /* Consume aio_notify() */
96 g_assert(!aio_poll(td.ctx, false));
97
98 /*
99 * Run the io_read() handler. This has the side-effect of activating
100 * polling in future aio_poll() calls.
101 */
102 g_assert(aio_poll(td.ctx, true));
103
104 /* The second time around the io_poll()/io_poll_ready() handler runs */
105 g_assert(aio_poll(td.ctx, true));
106
107 /* Run io_poll()/io_poll_ready() one more time to show it keeps working */
108 g_assert(aio_poll(td.ctx, true));
109
110 aio_set_event_notifier(td.ctx, &td.dummy_notifier, NULL, NULL, NULL);
111 aio_set_event_notifier(td.ctx, &td.poll_notifier, NULL, NULL, NULL);
112 event_notifier_cleanup(&td.dummy_notifier);
113 event_notifier_cleanup(&td.poll_notifier);
114 aio_context_unref(td.ctx);
115 }
116
main(int argc,char ** argv)117 int main(int argc, char **argv)
118 {
119 g_test_init(&argc, &argv, NULL);
120 g_test_add_func("/nested-aio-poll", test);
121 return g_test_run();
122 }
123