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c8bf923d5e
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Stefan Hajnoczi c8bf923d5e test-bdrv-drain: avoid race with BH in IOThread drain test 
This patch fixes a race condition in test-bdrv-drain that is difficult
to reproduce. test-bdrv-drain sometimes fails without an error message
on the block pull request sent by Kevin Wolf on Sep 4, 2023. I was able
to reproduce it locally and found that "block-backend: process I/O in
the current AioContext" (in this patch series) is the first commit where
it reproduces.

I do not know why "block-backend: process I/O in the current AioContext"
exposes this bug. It might be related to the fact that the test's preadv
request runs in the main thread instead of IOThread a after my commit.
That might simply change the timing of the test.

Now on to the race condition in test-bdrv-drain. The main thread
schedules a BH in IOThread a and then drains the BDS:

  aio_bh_schedule_oneshot(ctx_a, test_iothread_main_thread_bh, &data);

  /* The request is running on the IOThread a. Draining its block device
   * will make sure that it has completed as far as the BDS is concerned,
   * but the drain in this thread can continue immediately after
   * bdrv_dec_in_flight() and aio_ret might be assigned only slightly
   * later. */
  do_drain_begin(drain_type, bs);

If the BH completes before do_drain_begin() then there is nothing to
worry about.

If the BH invokes bdrv_flush() before do_drain_begin(), then
do_drain_begin() waits for it to complete.

The problematic case is when do_drain_begin() runs before the BH enters
bdrv_flush(). Then do_drain_begin() misses the BH and the drain
mechanism has failed in quiescing I/O.

Fix this by incrementing the in_flight counter so that do_drain_begin()
waits for test_iothread_main_thread_bh().

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230912231037.826804-3-stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-09-20 17:46:01 +02:00
..
check-block-qdict.c tests: unit: add NULL-pointer check 2022-09-18 09:17:41 +02:00
check-qdict.c
check-qjson.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
check-qlist.c
check-qlit.c
check-qnull.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
check-qnum.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
check-qobject.c tests: remove block/qdict checks from check-qobject.c 2022-04-21 17:03:51 +04:00
check-qom-interface.c
check-qom-proplist.c include: add qemu/keyval.h 2022-04-21 17:03:51 +04:00
check-qstring.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
crypto-tls-psk-helpers.c tests: avoid DOS line endings in PSK file 2022-10-27 11:55:41 +01:00
crypto-tls-psk-helpers.h tests: add migration tests of TLS with PSK credentials 2022-05-16 11:46:04 +01:00
crypto-tls-x509-helpers.c tests: fix encoding of IP addresses in x509 certs 2022-05-16 11:46:04 +01:00
crypto-tls-x509-helpers.h tests: add more helper macros for creating TLS x509 certs 2022-05-16 11:46:04 +01:00
io-channel-helpers.c tests/channel-helper: set blocking in main thread 2022-10-12 19:22:01 +04:00
io-channel-helpers.h
iothread.c async: the main AioContext is only "current" if under the BQL 2021-06-18 10:59:52 -05:00
iothread.h
meson.build configure, meson: remove target OS symbols from config-host.mak 2023-09-07 13:32:37 +02:00
pkix_asn1_tab.c tests: remove QCRYPTO_HAVE_TLS_TEST_SUPPORT 2021-06-25 10:53:46 +02:00
ptimer-test-stubs.c async: Add an optional reentrancy guard to the BH API 2023-04-28 11:31:07 +02:00
ptimer-test.c tests/unit: Replace g_memdup() by g_memdup2() 2022-07-18 20:24:36 +02:00
ptimer-test.h
rcutorture.c Updated the FSF address to <https://www.gnu.org/licenses/> 2023-02-27 09:15:39 +01:00
socket-helpers.c win32: replace closesocket() with close() wrapper 2023-03-13 15:39:31 +04:00
socket-helpers.h tests/unit: Update test-io-channel-socket.c for Windows 2022-09-02 15:54:47 +04:00
test-aio-multithread.c atomics: eliminate mb_read/mb_set 2023-06-06 09:42:14 +02:00
test-aio.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-authz-list.c
test-authz-listfile.c
test-authz-pam.c
test-authz-simple.c
test-base64.c
test-bdrv-drain.c test-bdrv-drain: avoid race with BH in IOThread drain test 2023-09-20 17:46:01 +02:00
test-bdrv-graph-mod.c block: Mark bdrv_parent_perms_conflict() and callers GRAPH_RDLOCK 2023-09-20 17:46:01 +02:00
test-bitcnt.c
test-bitmap.c
test-bitops.c
test-block-backend.c
test-block-iothread.c block: Take AioContext lock for bdrv_append() more consistently 2023-09-20 17:46:00 +02:00
test-blockjob-txn.c jobs: use job locks also in the unit tests 2022-10-07 12:11:41 +02:00
test-blockjob.c tests/unit/test-blockjob: Disable complete_in_standby test 2023-03-20 12:43:50 +01:00
test-bufferiszero.c
test-char.c qapi chardev: Elide redundant has_FOO in generated C 2022-12-14 20:04:47 +01:00
test-clone-visitor.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
test-coroutine.c coroutine: Clean up superfluous inclusion of qemu/lockable.h 2023-01-19 10:18:28 +01:00
test-crypto-afsplit.c
test-crypto-akcipher.c tests/crypto: Add test suite for RSA keys 2022-05-26 11:41:56 +01:00
test-crypto-block.c qapi crypto: Elide redundant has_FOO in generated C 2022-12-14 20:04:47 +01:00
test-crypto-cipher.c crypto: replace 'des-rfb' cipher with 'des' 2021-07-14 14:15:52 +01:00
test-crypto-der.c crypto: Support DER encodings 2022-11-02 06:56:32 -04:00
test-crypto-hash.c crypto: use &error_fatal in crypto tests 2021-07-14 14:15:52 +01:00
test-crypto-hmac.c crypto: use &error_fatal in crypto tests 2021-07-14 14:15:52 +01:00
test-crypto-ivgen.c crypto: skip essiv ivgen tests if AES+ECB isn't available 2021-07-14 14:15:52 +01:00
test-crypto-pbkdf.c crypto: remove obsolete crypto test condition 2021-07-14 14:15:52 +01:00
test-crypto-secret.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-crypto-tlscredsx509.c tests: Use g_mkdir_with_parents() 2022-08-25 15:24:09 +02:00
test-crypto-tlssession.c Call qemu_socketpair() instead of socketpair() when possible 2023-01-16 17:42:17 +01:00
test-crypto-xts.c
test-cutils.c cutils: Improve qemu_strtosz handling of fractions 2023-06-02 12:29:27 -05:00
test-div128.c host-utils: add unit tests for divu128/divs128 2021-10-27 17:10:00 -07:00
test-error-report.c error: add global &error_warn destination 2023-03-13 15:23:37 +04:00
test-forward-visitor.c include: add qemu/keyval.h 2022-04-21 17:03:51 +04:00
test-hbitmap.c Use g_new() & friends where that makes obvious sense 2022-03-21 15:44:44 +01:00
test-image-locking.c tests/unit/test-image-locking: Fix handling of temporary files 2022-10-12 12:48:53 +02:00
test-int128.c qemu/int128: add int128_urshift 2022-04-20 18:00:30 -03:00
test-interval-tree.c util: Add interval-tree.c 2022-12-20 17:09:41 -08:00
test-io-channel-buffer.c
test-io-channel-command.c tests: fix path separator, use g_build_filename() 2023-03-13 15:39:31 +04:00
test-io-channel-file.c tests: replace pipe() with g_unix_open_pipe(CLOEXEC) 2022-05-03 15:46:08 +04:00
test-io-channel-null.c io: add a QIOChannelNull equivalent to /dev/null 2022-06-22 18:11:21 +01:00
test-io-channel-socket.c io: Add support for MSG_PEEK for socket channel 2023-02-06 19:22:56 +01:00
test-io-channel-tls.c Call qemu_socketpair() instead of socketpair() when possible 2023-01-16 17:42:17 +01:00
test-io-task.c
test-iov.c tests/unit: Replace g_memdup() by g_memdup2() 2022-07-18 20:24:36 +02:00
test-keyval.c include: add qemu/keyval.h 2022-04-21 17:03:51 +04:00
test-logging.c util/log: Remove qemu_log_close 2022-04-20 10:51:11 -07:00
test-mul64.c
test-nested-aio-poll.c aio: remove aio_disable_external() API 2023-05-30 17:37:26 +02:00
test-opts-visitor.c
test-qapi-util.c
test-qdev-global-props.c
test-qdist.c
test-qemu-opts.c qemu-option: remove now-dead code 2021-07-06 08:33:51 +02:00
test-qga.c qga: Add tests for --allow-rpcs option 2023-07-10 15:54:40 +03:00
test-qgraph.c tests: Remove uses of deprecated raspi2/raspi3 machine names 2021-09-01 11:08:15 +01:00
test-qht.c
test-qmp-cmds.c tests: add G_GNUC_PRINTF for various functions 2023-01-11 10:44:34 +01:00
test-qmp-event.c qapi tests: Elide redundant has_FOO in generated C 2022-12-13 18:31:37 +01:00
test-qobject-input-visitor.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-qobject-output-visitor.c qapi: allow unions to contain further unions 2023-04-26 07:52:45 +02:00
test-qtree.c util: import GTree as QTree 2023-03-28 15:23:10 -07:00
test-rcu-list.c replace TABs with spaces 2023-03-20 12:43:50 +01:00
test-rcu-simpleq.c
test-rcu-slist.c
test-rcu-tailq.c
test-replication.c replication: move include out of root directory 2021-05-26 14:49:46 +02:00
test-seccomp.c Don't include headers already included by qemu/osdep.h 2023-02-08 07:28:05 +01:00
test-shift128.c
test-smp-parse.c tests/unit/test-smp-parse: Keep default MIN/MAX CPUs in machine_base_class_init 2021-12-31 13:42:48 +01:00
test-string-input-visitor.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
test-string-output-visitor.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
test-thread-pool.c tests: mark more coroutine_fns 2023-04-25 13:17:28 +02:00
test-throttle.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-timed-average.c
test-util-filemonitor.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-util-sockets.c Remove qemu-common.h include from most units 2022-04-06 14:31:55 +02:00
test-uuid.c
test-visitor-serialization.c qapi tests: Elide redundant has_FOO in generated C 2022-12-13 18:31:37 +01:00
test-vmstate.c test-vmstate: fix bad GTree usage, use-after-free 2023-03-02 17:06:27 +01:00
test-write-threshold.c write-threshold: deal with includes 2021-05-14 16:14:10 +02:00
test-x86-cpuid.c
test-xbzrle.c migration/xbzrle: Use i386 host/cpuinfo.h 2023-05-23 16:51:18 -07:00
test-xs-node.c tests/: spelling fixes 2023-09-08 13:08:52 +03:00
test-yank.c qapi: Convert simple union SocketAddressLegacy to flat one 2021-09-27 08:23:25 +02:00