- Waiting for global read lock：由于flush table with read lock调用函数lock_global_read_lock导致DML操作堵塞。
- Waiting for commit lock ：由于flush table with read lock 调用函数make_global_read_lock_block_commit导致事务不能提交
现象
堵塞COMMIT和DML
mysql> show processlist;
+----+-----------------+-----------+---------+---------+------+------------------------------+----------------------------+-----------+---------------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined |
+----+-----------------+-----------+---------+---------+------+------------------------------+----------------------------+-----------+---------------+
| 1 | event_scheduler | localhost | NULL | Daemon | 268 | Waiting on empty queue | NULL | 0 | 0 |
| 5 | root | localhost | NULL | Query | 0 | starting | show processlist | 0 | 0 |
| 6 | root | localhost | testmts | Query | 61 | Waiting for commit lock | commit | 0 | 0 |
| 7 | root | localhost | testmts | Query | 6 | Waiting for global read lock | delete from testcp limit 1 | 0 | 0 |
+----+-----------------+-----------+---------+---------+------+------------------------------+----------------------------+-----------+---------------+相关栈帧
Waiting for commit lock
#0 0x00007ffff7bd3a5e in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x000000000192027b in native_cond_timedwait (cond=0x7ffee0000d08, mutex=0x7ffee0000cc0, abstime=0x7fffec5ec950)
at /mysqldata/percona-server-locks-detail-5.7.22/include/thr_cond.h:129
#2 0x00000000019205ea in safe_cond_timedwait (cond=0x7ffee0000d08, mp=0x7ffee0000c98, abstime=0x7fffec5ec950,
file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", line=1899) at /mysqldata/percona-server-locks-detail-5.7.22/mysys/thr_cond.c:88
#3 0x00000000014b9f21 in my_cond_timedwait (cond=0x7ffee0000d08, mp=0x7ffee0000c98, abstime=0x7fffec5ec950,
file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", line=1899) at /mysqldata/percona-server-locks-detail-5.7.22/include/thr_cond.h:180
#4 0x00000000014ba484 in inline_mysql_cond_timedwait (that=0x7ffee0000d08, mutex=0x7ffee0000c98, abstime=0x7fffec5ec950,
src_file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", src_line=1899)
at /mysqldata/percona-server-locks-detail-5.7.22/include/mysql/psi/mysql_thread.h:1229
#5 0x00000000014bb702 in MDL_wait::timed_wait (this=0x7ffee0000c98, owner=0x7ffee0000c00, abs_timeout=0x7fffec5ec950, set_status_on_timeout=true,
wait_state_name=0x2d93240) at /mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc:1899
#6 0x00000000014bd7ac in MDL_context::acquire_lock (this=0x7ffee0000c98, mdl_request=0x7fffec5ec9c0, lock_wait_timeout=31536000)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc:3746
#7 0x0000000000f7ffe4 in ha_commit_trans (thd=0x7ffee0000c00, all=true, ignore_global_read_lock=false)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/handler.cc:1795
#8 0x00000000016dcd2f in trans_commit (thd=0x7ffee0000c00) at /mysqldata/percona-server-locks-detail-5.7.22/sql/transaction.cc:239
#9 0x00000000015cf466 in mysql_execute_command (thd=0x7ffee0000c00, first_level=true) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:4526
#10 0x00000000015d2fde in mysql_parse (thd=0x7ffee0000c00, parser_state=0x7fffec5ee600) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:5901
#11 0x00000000015c6b72 in dispatch_command (thd=0x7ffee0000c00, com_data=0x7fffec5eed70, command=COM_QUERY)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:1490
#12 0x00000000015c58ff in do_command (thd=0x7ffee0000c00) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:1021
#13 0x000000000170e578 in handle_connection (arg=0x67bf490) at /mysqldata/percona-server-locks-detail-5.7.22/sql/conn_handler/connection_handler_per_thread.cc:312
#14 0x0000000001945538 in pfs_spawn_thread (arg=0x66ff4f0) at /mysqldata/percona-server-locks-detail-5.7.22/storage/perfschema/pfs.cc:2190
#15 0x00007ffff7bcfaa1 in start_thread () from /lib64/libpthread.so.0
#16 0x00007ffff6b37c4d in clone () from /lib64/libc.so.6Waiting for global read lock
#0 0x00007ffff7bd3a5e in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x000000000192027b in native_cond_timedwait (cond=0x7ffee4000c98, mutex=0x7ffee4000c50, abstime=0x7fffec58a0e0)
at /mysqldata/percona-server-locks-detail-5.7.22/include/thr_cond.h:129
#2 0x00000000019205ea in safe_cond_timedwait (cond=0x7ffee4000c98, mp=0x7ffee4000c28, abstime=0x7fffec58a0e0,
file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", line=1899) at /mysqldata/percona-server-locks-detail-5.7.22/mysys/thr_cond.c:88
#3 0x00000000014b9f21 in my_cond_timedwait (cond=0x7ffee4000c98, mp=0x7ffee4000c28, abstime=0x7fffec58a0e0,
file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", line=1899) at /mysqldata/percona-server-locks-detail-5.7.22/include/thr_cond.h:180
#4 0x00000000014ba484 in inline_mysql_cond_timedwait (that=0x7ffee4000c98, mutex=0x7ffee4000c28, abstime=0x7fffec58a0e0,
src_file=0x204cdd0 "/mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc", src_line=1899)
at /mysqldata/percona-server-locks-detail-5.7.22/include/mysql/psi/mysql_thread.h:1229
#5 0x00000000014bb702 in MDL_wait::timed_wait (this=0x7ffee4000c28, owner=0x7ffee4000b90, abs_timeout=0x7fffec58a0e0, set_status_on_timeout=true,
wait_state_name=0x2d93180) at /mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc:1899
#6 0x00000000014bd7ac in MDL_context::acquire_lock (this=0x7ffee4000c28, mdl_request=0x7fffec58a160, lock_wait_timeout=31536000)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/mdl.cc:3746
#7 0x000000000153bed8 in open_table (thd=0x7ffee4000b90, table_list=0x7ffee40066e0, ot_ctx=0x7fffec58a5a0)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_base.cc:3233
#8 0x000000000153f904 in open_and_process_table (thd=0x7ffee4000b90, lex=0x7ffee40031c0, tables=0x7ffee40066e0, counter=0x7ffee4003280, flags=0,
prelocking_strategy=0x7fffec58a6d0, has_prelocking_list=false, ot_ctx=0x7fffec58a5a0) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_base.cc:5213
#9 0x0000000001540a58 in open_tables (thd=0x7ffee4000b90, start=0x7fffec58a690, counter=0x7ffee4003280, flags=0, prelocking_strategy=0x7fffec58a6d0)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_base.cc:5831
#10 0x0000000001541e93 in open_tables_for_query (thd=0x7ffee4000b90, tables=0x7ffee40066e0, flags=0)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_base.cc:6606
#11 0x00000000017f2b53 in Sql_cmd_delete::mysql_delete (this=0x7ffee4006c80, thd=0x7ffee4000b90, limit=1)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_delete.cc:76
#12 0x00000000017f7098 in Sql_cmd_delete::execute (this=0x7ffee4006c80, thd=0x7ffee4000b90) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_delete.cc:1386
#13 0x00000000015cc801 in mysql_execute_command (thd=0x7ffee4000b90, first_level=true) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:3756
#14 0x00000000015d2fde in mysql_parse (thd=0x7ffee4000b90, parser_state=0x7fffec58c600) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:5901
#15 0x00000000015c6b72 in dispatch_command (thd=0x7ffee4000b90, com_data=0x7fffec58cd70, command=COM_QUERY)
at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:1490
#16 0x00000000015c58ff in do_command (thd=0x7ffee4000b90) at /mysqldata/percona-server-locks-detail-5.7.22/sql/sql_parse.cc:1021
#17 0x000000000170e578 in handle_connection (arg=0x67182c0) at /mysqldata/percona-server-locks-detail-5.7.22/sql/conn_handler/connection_handler_per_thread.cc:312
#18 0x0000000001945538 in pfs_spawn_thread (arg=0x671aca0) at /mysqldata/percona-server-locks-detail-5.7.22/storage/perfschema/pfs.cc:2190
#19 0x00007ffff7bcfaa1 in start_thread () from /lib64/libpthread.so.0
#20 0x00007ffff6b37c4d in clone () from /lib64/libc.so.6
