@samitouri / QOSamiQemu
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1 /*
2 * SPDX-License-Identifier: GPL-2.0-or-later
3 *
4 * BlockAcctStats latency histogram locking regression test
5 *
6 * Copyright (c) 2026 Virtuozzo International GmbH.
7 *
8 * Regression test for missing stats->lock in
9 * block_latency_histogram_set()/block_latency_histograms_clear(),
10 * racing block_account_one_io() reading the same fields from an
11 * iothread. Aborts reliably before the fix, passes after it.
12 */
13
14 #include "qemu/osdep.h"
15 #include "block/block.h"
16 #include "block/accounting.h"
17 #include "system/block-backend.h"
18 #include "system/block-backend-io.h"
19 #include "qapi/error.h"
20 #include "qemu/main-loop.h"
21 #include "qemu/thread.h"
22
23 #define RACE_DURATION_MS 2000
24 #define NUM_READER_THREADS 8
25
26 static bool stop_workers;
27
28 /*
29 * Different bin counts, so the writer's g_free()/g_new() churn can be
30 * caught mid-update. Values are small enough (nanoseconds) that plain
31 * back-to-back start/done calls exercise every bin without sleeping.
32 */
33 static uint64List boundaries_a[] = {
34 { .next = &boundaries_a[1], .value = 1000 },
35 { .next = &boundaries_a[2], .value = 5000 },
36 { .next = NULL, .value = 50000 },
37 };
38
39 static uint64List boundaries_b[] = {
40 { .next = &boundaries_b[1], .value = 800 },
41 { .next = &boundaries_b[2], .value = 3000 },
42 { .next = &boundaries_b[3], .value = 20000 },
43 { .next = NULL, .value = 200000 },
44 };
45
46 static void *writer_thread(void *opaque)
47 {
48 BlockAcctStats *stats = opaque;
49
50 while (!qatomic_read(&stop_workers)) {
51 block_latency_histogram_set(stats, BLOCK_ACCT_READ, boundaries_a);
52 block_latency_histogram_set(stats, BLOCK_ACCT_READ, boundaries_b);
53 block_latency_histograms_clear(stats);
54 }
55
56 return NULL;
57 }
58
59 static void *reader_thread(void *opaque)
60 {
61 BlockAcctStats *stats = opaque;
62
63 while (!qatomic_read(&stop_workers)) {
64 BlockAcctCookie cookie;
65
66 block_acct_start(stats, &cookie, 4096, BLOCK_ACCT_READ);
67 block_acct_done(stats, &cookie);
68 }
69
70 return NULL;
71 }
72
73 static void test_latency_histogram_race(void)
74 {
75 BlockBackend *blk = blk_new(qemu_get_aio_context(),
76 BLK_PERM_ALL, BLK_PERM_ALL);
77 BlockAcctStats *stats = blk_get_stats(blk);
78 QemuThread writer, readers[NUM_READER_THREADS];
79 int i;
80
81 /* Histogram has to be enabled (bins != NULL) before racing it. */
82 g_assert(block_latency_histogram_set(stats, BLOCK_ACCT_READ,
83 boundaries_a) == 0);
84
85 stop_workers = false;
86 qemu_thread_create(&writer, "hist-writer", writer_thread, stats,
87 QEMU_THREAD_JOINABLE);
88 for (i = 0; i < NUM_READER_THREADS; i++) {
89 qemu_thread_create(&readers[i], "hist-reader", reader_thread, stats,
90 QEMU_THREAD_JOINABLE);
91 }
92
93 g_usleep(RACE_DURATION_MS * 1000);
94 qatomic_set(&stop_workers, true);
95
96 qemu_thread_join(&writer);
97 for (i = 0; i < NUM_READER_THREADS; i++) {
98 qemu_thread_join(&readers[i]);
99 }
100
101 blk_unref(blk);
102 }
103
104 int main(int argc, char **argv)
105 {
106 bdrv_init();
107 qemu_init_main_loop(&error_abort);
108
109 g_test_init(&argc, &argv, NULL);
110
111 g_test_add_func("/block-accounting/latency_histogram_race",
112 test_latency_histogram_race);
113
114 return g_test_run();
115 }