Bug #76953: Many IPv6-specific tests fail due to missing IPv6 support #13
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Fixed a number of IPv6-specific tests so that checks for IPv6 work as intended: skip test when IPv6 support is unavailable instead of failing with an error on server startup.
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bjornmu
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that referenced
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Apr 10, 2017
Patch #13: Fix -Wunused-parameter warnings in sql*, part 3.
surbhat1595
pushed a commit
that referenced
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Apr 25, 2019
…E TO A SERVER
Problem
========================================================================
Running the GCS tests with ASAN seldomly reports a user-after-free of
the server reference that the acceptor_learner_task uses.
Here is an excerpt of ASAN's output:
==43936==ERROR: AddressSanitizer: heap-use-after-free on address 0x63100021c840 at pc 0x000000530ff8 bp 0x7fc0427e8530 sp 0x7fc0427e8520
WRITE of size 8 at 0x63100021c840 thread T3
#0 0x530ff7 in server_detected /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:962
#1 0x533814 in buffered_read_bytes /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:1249
#2 0x5481af in buffered_read_msg /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:1399
#3 0x51e171 in acceptor_learner_task /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:4690
#4 0x562357 in task_loop /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/task.c:1140
#5 0x5003b2 in xcom_taskmain2 /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:1324
#6 0x6a278a in Gcs_xcom_proxy_impl::xcom_init(unsigned short, node_address*) /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_proxy.cc:164
#7 0x59b3c1 in xcom_taskmain_startup /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_control_interface.cc:107
#8 0x7fc04a2e4dd4 in start_thread (/lib64/libpthread.so.0+0x7dd4)
#9 0x7fc047ff2bfc in __clone (/lib64/libc.so.6+0xfebfc)
0x63100021c840 is located 64 bytes inside of 65688-byte region [0x63100021c800,0x63100022c898)
freed by thread T3 here:
#0 0x7fc04a5d7508 in __interceptor_free (/lib64/libasan.so.4+0xde508)
#1 0x52cf86 in freesrv /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:836
#2 0x52ea78 in srv_unref /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:868
#3 0x524c30 in reply_handler_task /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:4914
#4 0x562357 in task_loop /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/task.c:1140
#5 0x5003b2 in xcom_taskmain2 /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:1324
#6 0x6a278a in Gcs_xcom_proxy_impl::xcom_init(unsigned short, node_address*) /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_proxy.cc:164
#7 0x59b3c1 in xcom_taskmain_startup /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_control_interface.cc:107
#8 0x7fc04a2e4dd4 in start_thread (/lib64/libpthread.so.0+0x7dd4)
previously allocated by thread T3 here:
#0 0x7fc04a5d7a88 in __interceptor_calloc (/lib64/libasan.so.4+0xdea88)
#1 0x543604 in mksrv /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:721
#2 0x543b4c in addsrv /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:755
#3 0x54af61 in update_servers /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_transport.c:1747
#4 0x501082 in site_install_action /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:1572
#5 0x55447c in import_config /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/site_def.c:486
#6 0x506dfc in handle_x_snapshot /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:5257
#7 0x50c444 in xcom_fsm /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:5325
#8 0x516c36 in dispatch_op /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:4510
#9 0x521997 in acceptor_learner_task /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:4772
#10 0x562357 in task_loop /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/task.c:1140
#11 0x5003b2 in xcom_taskmain2 /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/xcom/xcom_base.c:1324
#12 0x6a278a in Gcs_xcom_proxy_impl::xcom_init(unsigned short, node_address*) /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_proxy.cc:164
#13 0x59b3c1 in xcom_taskmain_startup /home/tvale/mysql/plugin/group_replication/libmysqlgcs/src/bindings/xcom/gcs_xcom_control_interface.cc:107
#14 0x7fc04a2e4dd4 in start_thread (/lib64/libpthread.so.0+0x7dd4)
Analysis
========================================================================
The server structure is reference counted by the associated sender_task
and reply_handler_task.
When they finish, they unreference the server, which leads to its memory
being freed.
However, the acceptor_learner_task keeps a "naked" reference to the
server structure.
Under the right ordering of operations, i.e. the sender_task and
reply_handler_task terminating after the acceptor_learner_task acquires,
but before it uses, the reference to the server structure, leads to the
acceptor_learner_task accessing the server structure after it has been
freed.
Solution
========================================================================
Let the acceptor_learner_task also reference count the server structure
so it is not freed while still in use.
Reviewed-by: André Negrão <[email protected]>
Reviewed-by: Venkatesh Venugopal <[email protected]>
RB: 21209
dveeden
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May 5, 2023
Create a compatibility layer that can allow application-level code in NDB to make unconditional use of the OpenSSL 3.0 API. Change-Id: Ic31e238c58b3fd5c9237c6d4364b2bca4d02cdd7
bjornmu
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Oct 25, 2023
As a prerequisite for MTR testing, add support for the --ndb-tls-search-path and --ndb-mgm-tls options in ndb_waiter. A new MTR test require_mgm_tls demonstrates that cluster can run with [MGM]RequireTls=1 and --ndb-mgm-tls=strict A new MTR test api_require_trp demonstrates that an API node (ndb_desc) fails to connect to cluster when it does not have a certificate, but some data node requires TLS. Change-Id: I50595a7d9d2bbb8bb3a47d7640017a4101c41a30
bjornmu
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Jan 16, 2024
Post push fix. Change printout 'Using TLS' to ' trying TLS' added to printout of 'Connecting to management server ...' line for ndb_waiter tool. Adjust test ndb.ndb_tools_result to ignore wheter TLS is tried or not to be able to run test suite ndb with or without TLS. Change-Id: I6fb98b20eda21871248f3b85586c8f2a4cce93eb
venkatesh-prasad-v
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Jan 26, 2024
…and a local
DDL executed
https://bugs.mysql.com/bug.php?id=113727
Problem
-------
In high concurrency scenarios, MySQL replica can enter into a deadlock due to a
race condition between the replica applier thread and the client thread
performing a binlog group commit.
Analysis
--------
It needs at least 3 threads for this deadlock to happen
1. One client thread
2. Two replica applier threads
How this deadlock happens?
--------------------------
0. Binlog is enabled on replica, but log_replica_updates is disabled.
1. Initially, both "Commit Order" and "Binlog Flush" queues are empty.
2. Replica applier thread 1 enters the group commit pipeline to register in the
"Commit Order" queue since `log-replica-updates` is disabled on the replica
node.
3. Since both "Commit Order" and "Binlog Flush" queues are empty, the applier
thread 1
3.1. Becomes leader (In Commit_stage_manager::enroll_for()).
3.2. Registers in the commit order queue.
3.3. Acquires the lock MYSQL_BIN_LOG::LOCK_log.
3.4. Commit Order queue is emptied, but the lock MYSQL_BIN_LOG::LOCK_log is
not yet released.
NOTE: SE commit for applier thread is already done by the time it reaches
here.
4. Replica applier thread 2 enters the group commit pipeline to register in the
"Commit Order" queue since `log-replica-updates` is disabled on the replica
node.
5. Since the "Commit Order" queue is empty (emptied by applier thread 1 in 3.4), the
applier thread 2
5.1. Becomes leader (In Commit_stage_manager::enroll_for())
5.2. Registers in the commit order queue.
5.3. Tries to acquire the lock MYSQL_BIN_LOG::LOCK_log. Since it is held by applier
thread 1 it will wait until the lock is released.
6. Client thread enters the group commit pipeline to register in the
"Binlog Flush" queue.
7. Since "Commit Order" queue is not empty (there is applier thread 2 in the
queue), it enters the conditional wait `m_stage_cond_leader` with an
intention to become the leader for both the "Binlog Flush" and
"Commit Order" queues.
8. Applier thread 1 releases the lock MYSQL_BIN_LOG::LOCK_log and proceeds to update
the GTID by calling gtid_state->update_commit_group() from
Commit_order_manager::flush_engine_and_signal_threads().
9. Applier thread 2 acquires the lock MYSQL_BIN_LOG::LOCK_log.
9.1. It checks if there is any thread waiting in the "Binlog Flush" queue
to become the leader. Here it finds the client thread waiting to be
the leader.
9.2. It releases the lock MYSQL_BIN_LOG::LOCK_log and signals on the
cond_var `m_stage_cond_leader` and enters a conditional wait until the
thread's `tx_commit_pending` is set to false by the client thread
(will be done in the
Commit_stage_manager::process_final_stage_for_ordered_commit_group()
called by client thread from fetch_and_process_flush_stage_queue()).
10. The client thread wakes up from the cond_var `m_stage_cond_leader`. The
thread has now become a leader and it is its responsibility to update GTID
of applier thread 2.
10.1. It acquires the lock MYSQL_BIN_LOG::LOCK_log.
10.2. Returns from `enroll_for()` and proceeds to process the
"Commit Order" and "Binlog Flush" queues.
10.3. Fetches the "Commit Order" and "Binlog Flush" queues.
10.4. Performs the storage engine flush by calling ha_flush_logs() from
fetch_and_process_flush_stage_queue().
10.5. Proceeds to update the GTID of threads in "Commit Order" queue by
calling gtid_state->update_commit_group() from
Commit_stage_manager::process_final_stage_for_ordered_commit_group().
11. At this point, we will have
- Client thread performing GTID update on behalf if applier thread 2 (from step 10.5), and
- Applier thread 1 performing GTID update for itself (from step 8).
Due to the lack of proper synchronization between the above two threads,
there exists a time window where both threads can call
gtid_state->update_commit_group() concurrently.
In subsequent steps, both threads simultaneously try to modify the contents
of the array `commit_group_sidnos` which is used to track the lock status of
sidnos. This concurrent access to `update_commit_group()` can cause a
lock-leak resulting in one thread acquiring the sidno lock and not
releasing at all.
-----------------------------------------------------------------------------------------------------------
Client thread Applier Thread 1
-----------------------------------------------------------------------------------------------------------
update_commit_group() => global_sid_lock->rdlock(); update_commit_group() => global_sid_lock->rdlock();
calls update_gtids_impl_lock_sidnos() calls update_gtids_impl_lock_sidnos()
set commit_group_sidno[2] = true set commit_group_sidno[2] = true
lock_sidno(2) -> successful
lock_sidno(2) -> waits
update_gtids_impl_own_gtid() -> Add the thd->owned_gtid in `executed_gtids()`
if (commit_group_sidnos[2]) {
unlock_sidno(2);
commit_group_sidnos[2] = false;
}
Applier thread continues..
lock_sidno(2) -> successful
update_gtids_impl_own_gtid() -> Add the thd->owned_gtid in `executed_gtids()`
if (commit_group_sidnos[2]) { <=== this check fails and lock is not released.
unlock_sidno(2);
commit_group_sidnos[2] = false;
}
Client thread continues without releasing the lock
-----------------------------------------------------------------------------------------------------------
12. As the above lock-leak can also happen the other way i.e, the applier
thread fails to unlock, there can be different consequences hereafter.
13. If the client thread continues without releasing the lock, then at a later
stage, it can enter into a deadlock with the applier thread performing a
GTID update with stack trace.
Client_thread
-------------
mysql#1 __GI___lll_lock_wait
mysql#2 ___pthread_mutex_lock
mysql#3 native_mutex_lock <= waits for commit lock while holding sidno lock
mysql#4 Commit_stage_manager::enroll_for
mysql#5 MYSQL_BIN_LOG::change_stage
mysql#6 MYSQL_BIN_LOG::ordered_commit
mysql#7 MYSQL_BIN_LOG::commit
mysql#8 ha_commit_trans
mysql#9 trans_commit_implicit
mysql#10 mysql_create_like_table
mysql#11 Sql_cmd_create_table::execute
mysql#12 mysql_execute_command
mysql#13 dispatch_sql_command
Applier thread
--------------
mysql#1 ___pthread_mutex_lock
mysql#2 native_mutex_lock
mysql#3 safe_mutex_lock
mysql#4 Gtid_state::update_gtids_impl_lock_sidnos <= waits for sidno lock
mysql#5 Gtid_state::update_commit_group
mysql#6 Commit_order_manager::flush_engine_and_signal_threads <= acquires commit lock here
mysql#7 Commit_order_manager::finish
mysql#8 Commit_order_manager::wait_and_finish
mysql#9 ha_commit_low
mysql#10 trx_coordinator::commit_in_engines
mysql#11 MYSQL_BIN_LOG::commit
mysql#12 ha_commit_trans
mysql#13 trans_commit
mysql#14 Xid_log_event::do_commit
mysql#15 Xid_apply_log_event::do_apply_event_worker
mysql#16 Slave_worker::slave_worker_exec_event
mysql#17 slave_worker_exec_job_group
mysql#18 handle_slave_worker
14. If the applier thread continues without releasing the lock, then at a later
stage, it can perform recursive locking while setting the GTID for the next
transaction (in set_gtid_next()).
In debug builds the above case hits the assertion
`safe_mutex_assert_not_owner()` meaning the lock is already acquired by the
replica applier thread when it tries to re-acquire the lock.
Solution
--------
In the above problematic example, when seen from each thread
individually, we can conclude that there is no problem in the order of lock
acquisition, thus there is no need to change the lock order.
However, the root cause for this problem is that multiple threads can
concurrently access to the array `Gtid_state::commit_group_sidnos`.
In its initial implementation, it was expected that threads should
hold the `MYSQL_BIN_LOG::LOCK_commit` before modifying its contents. But it
was not considered when upstream implemented WL#7846 (MTS:
slave-preserve-commit-order when log-slave-updates/binlog is disabled).
With this patch, we now ensure that `MYSQL_BIN_LOG::LOCK_commit` is acquired
when the client thread (binlog flush leader) when it tries to perform GTID
update on behalf of threads waiting in "Commit Order" queue, thus providing a
guarantee that `Gtid_state::commit_group_sidnos` array is never accessed
without the protection of `MYSQL_BIN_LOG::LOCK_commit`.
bjornmu
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Apr 30, 2024
When built with ASAN, a use-after-free is reported for the TcpPortPool.
AddressSanitizer: heap-use-after-free on address 0x60200019f190 at pc
0x00000076a18d bp 0x7fff51e7d1d0 sp 0x7fff51e7d1c0
#4 0x770b73 in UniqueId::ProcessUniqueIds::erase(unsigned int)
../router/tests/helpers/tcp_port_pool.h:112
#5 0x770c48 in UniqueId::~UniqueId()
../router/tests/helpers/tcp_port_pool.cc:234
...
#12 0x82faa3 in testing::UnitTest::~UnitTest()
../extra/googletest/googletest-release-1.12.0/googletest/src/gtest.cc:5496
#13 0x7f5fe085ace8 in __run_exit_handlers (/lib64/libc.so.6+0x39ce8)
0x60200019f190 is located 0 bytes inside of 16-byte region
[0x60200019f190,0x60200019f1a0)
freed by thread T0 here:
#0 0x7f5fe3cbd10f in operator delete(void*, unsigned long)
(/lib64/libasan.so.6+0xb710f)
#1 0x7f5fe085ace8 in __run_exit_handlers (/lib64/libc.so.6+0x39ce8)
Background
==========
__run_exit_handlers destroys "static" and "global" variables in reverse
order of their creation.
googletest's unit-tests are a static, and the TcpPortPool also has
ProcessUniqueId's which contains the process-wide unique-ids.
At construct: unittest -> tcp-port-pool -> proces-unique-ids
At destruct : process-unique-ids -> tcp-port-pool -> 💥
The use-after-free happens as the process-unique-ids static is
destructed before the tcp-port-pool which tries to its Ids from the
process-unique-ids.
Change
======
- extend the lifetime of the process-unique-ids to after the last use of
the tcp-port-pool via a std::shared_ptr<>
Change-Id: I75b8b781e1d240f18ca72f2c86182639a7699f06
bjornmu
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that referenced
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Jul 1, 2024
… for connection xxx'.
The new iterator based explains are not impacted.
The issue here is a race condition. More than one thread is using the
query term iterator at the same time (whoch is neithe threas safe nor
reantrant), and part of its state is in the query terms being visited
which leads to interference/race conditions.
a) the explain thread
uses an iterator here:
Sql_cmd_explain_other_thread::execute
is inspecting the Query_expression of the running query
calling master_query_expression()->find_blocks_query_term which uses
an iterator over the query terms in the query expression:
for (auto qt : query_terms<>()) {
if (qt->query_block() == qb) {
return qt;
}
}
the above search fails to find qb due to the interference of the
thread b), see below, and then tries to access a nullpointer:
* thread #36, name = ‘connection’, stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
frame #0: 0x000000010bb3cf0d mysqld`Query_block::type(this=0x00007f8f82719088) const at sql_lex.cc:4441:11
frame #1: 0x000000010b83763e mysqld`(anonymous namespace)::Explain::explain_select_type(this=0x00007000020611b8) at opt_explain.cc:792:50
frame #2: 0x000000010b83cc4d mysqld`(anonymous namespace)::Explain_join::explain_select_type(this=0x00007000020611b8) at opt_explain.cc:1487:21
frame #3: 0x000000010b837c34 mysqld`(anonymous namespace)::Explain::prepare_columns(this=0x00007000020611b8) at opt_explain.cc:744:26
frame #4: 0x000000010b83ea0e mysqld`(anonymous namespace)::Explain_join::explain_qep_tab(this=0x00007000020611b8, tabnum=0) at opt_explain.cc:1415:32
frame #5: 0x000000010b83ca0a mysqld`(anonymous namespace)::Explain_join::shallow_explain(this=0x00007000020611b8) at opt_explain.cc:1364:9
frame #6: 0x000000010b83379b mysqld`(anonymous namespace)::Explain::send(this=0x00007000020611b8) at opt_explain.cc:770:14
frame #7: 0x000000010b834147 mysqld`explain_query_specification(explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00, query_term=0x00007f8f82719088, ctx=CTX_JOIN) at opt_explain.cc:2088:20
frame #8: 0x000000010bd36b91 mysqld`Query_expression::explain_query_term(this=0x00007f8f7a090360, explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00, qt=0x00007f8f82719088) at sql_union.cc:1519:11
frame #9: 0x000000010bd36c68 mysqld`Query_expression::explain_query_term(this=0x00007f8f7a090360, explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00, qt=0x00007f8f8271d748) at sql_union.cc:1526:13
frame #10: 0x000000010bd373f7 mysqld`Query_expression::explain(this=0x00007f8f7a090360, explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00) at sql_union.cc:1591:7
frame #11: 0x000000010b835820 mysqld`mysql_explain_query_expression(explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00, unit=0x00007f8f7a090360) at opt_explain.cc:2392:17
frame #12: 0x000000010b835400 mysqld`explain_query(explain_thd=0x00007f8fbb111e00, query_thd=0x00007f8fbb919c00, unit=0x00007f8f7a090360) at opt_explain.cc:2353:13
* frame #13: 0x000000010b8363e4 mysqld`Sql_cmd_explain_other_thread::execute(this=0x00007f8fba585b68, thd=0x00007f8fbb111e00) at opt_explain.cc:2531:11
frame #14: 0x000000010bba7d8b mysqld`mysql_execute_command(thd=0x00007f8fbb111e00, first_level=true) at sql_parse.cc:4648:29
frame #15: 0x000000010bb9e230 mysqld`dispatch_sql_command(thd=0x00007f8fbb111e00, parser_state=0x0000700002065de8) at sql_parse.cc:5303:19
frame #16: 0x000000010bb9a4cb mysqld`dispatch_command(thd=0x00007f8fbb111e00, com_data=0x0000700002066e38, command=COM_QUERY) at sql_parse.cc:2135:7
frame #17: 0x000000010bb9c846 mysqld`do_command(thd=0x00007f8fbb111e00) at sql_parse.cc:1464:18
frame #18: 0x000000010b2f2574 mysqld`handle_connection(arg=0x0000600000e34200) at connection_handler_per_thread.cc:304:13
frame #19: 0x000000010e072fc4 mysqld`pfs_spawn_thread(arg=0x00007f8fba8160b0) at pfs.cc:3051:3
frame #20: 0x00007ff806c2b202 libsystem_pthread.dylib`_pthread_start + 99
frame #21: 0x00007ff806c26bab libsystem_pthread.dylib`thread_start + 15
b) the query thread being explained is itself performing LEX::cleanup
and as part of the iterates over the query terms, but still allows
EXPLAIN of the query plan since
thd->query_plan.set_query_plan(SQLCOM_END, ...)
hasn't been called yet.
20:frame: Query_terms<(Visit_order)1, (Visit_leaves)0>::Query_term_iterator::operator++() (in mysqld) (query_term.h:613)
21:frame: Query_expression::cleanup(bool) (in mysqld) (sql_union.cc:1861)
22:frame: LEX::cleanup(bool) (in mysqld) (sql_lex.h:4286)
30:frame: Sql_cmd_dml::execute(THD*) (in mysqld) (sql_select.cc:799)
31:frame: mysql_execute_command(THD*, bool) (in mysqld) (sql_parse.cc:4648)
32:frame: dispatch_sql_command(THD*, Parser_state*) (in mysqld) (sql_parse.cc:5303)
33:frame: dispatch_command(THD*, COM_DATA const*, enum_server_command) (in mysqld) (sql_parse.cc:2135)
34:frame: do_command(THD*) (in mysqld) (sql_parse.cc:1464)
57:frame: handle_connection(void*) (in mysqld) (connection_handler_per_thread.cc:304)
58:frame: pfs_spawn_thread(void*) (in mysqld) (pfs.cc:3053)
65:frame: _pthread_start (in libsystem_pthread.dylib) + 99
66:frame: thread_start (in libsystem_pthread.dylib) + 15
Solution:
This patch solves the issue by removing iterator state from
Query_term, making the query_term iterators thread safe. This solution
labels every child query_term with its index in its parent's
m_children vector. The iterator can therefore easily compute the next
child to visit based on Query_term::m_sibling_idx.
A unit test case is added to check reentrancy.
One can also manually verify that we have no remaining race condition
by running two client connections files (with \. <file>) with a big
number of copies of the repro query in one connection and a big number
of EXPLAIN format=json FOR <connection>, e.g.
EXPLAIN FORMAT=json FOR CONNECTION 8\G
in the other. The actual connection number would need to verified
in connection one, of course.
Change-Id: Ie7d56610914738ccbbecf399ccc4f465f7d26ea7
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Fixed a number of IPv6-specific tests so that checks for IPv6 work as
intended: skip test when IPv6 support is unavailable instead of failing
with an error on server startup.