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###############################################################################
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# Bug#17283409 4-WAY DEADLOCK: ZOMBIES, PURGING BINLOGS, SHOW PROCESSLIST,
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# Problem: A deadlock was occuring when 4 threads were involved in acquiring
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# Thread 1: Dump thread ( Slave is reconnecting, so on Master, a new dump
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# thread is trying kill zombie dump threads. It acquired
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# thread's LOCK_thd_data and it is about to acquire
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# mysys_var->current_mutex ( which LOCK_log)
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# Thread 2: Application thread is executing show binlogs and acquired
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# LOCK_log and it is about to acquire LOCK_index.
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# Thread 3: Applicaiton thread is executing Purge binary logs and acquired
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# LOCK_index and it is about to acquire LOCK_thread_count.
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# Thread 4: Application thread is executing show processlist and acquired
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# LOCK_thread_count and it is about to acquire zombie dump
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# thread's LOCK_thd_data.
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# Deadlock : Thread 1 -> Thread 2 -> Thread 3-> Thread 4 -> Thread 1
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# The same above deadlock was observed when thread 4 is replaced with another
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# thread which is executing 'SELECT * FROM information_schema.processlist'
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# command and acquired LOCK_thread_count and it is about to acquire zombie
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# dump thread's LOCK_thd_data.
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# Fix: Introuced a new lock (Lock_thread_remove) which will guard the thread
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# deletion (exit process) and the same lock is used in show processlist
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# execution instead of LOCK_thread_count. i.e., After the patch, Server allows
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# new threads to join the system but it will not any threads to execute its
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# 'cleanup' process. Now the new lock order is: LOCK_thread_remove ->
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# LOCK_thd_data -> LOCK_log -> LOCK_index -> LOCK_thread_count Both the above
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# scenarios are tested with the below test code and it proves that there is no
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# deadlock after the fix.
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###############################################################################
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--source include/have_debug_sync.inc
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--source include/have_binlog_format_statement.inc
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--source include/master-slave.inc
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connect(master2,127.0.0.1,root,,test,$MASTER_MYPORT,);
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connect(master3,127.0.0.1,root,,test,$MASTER_MYPORT,);
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# Create atleast one binary log, otherwise purge logs command, show binary
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# logs command do not hit the DEBUG_SYNC points.
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SET @save_debug=@@global.debug;
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SET GLOBAL DEBUG='+d,before_dump_thread_acquires_current_mutex,processlist_acquiring_dump_threads_LOCK_thd_data';
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# Iteration 1 with "SHOW PROCESSLIST command"
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# Iteration 2 with "SELECT * FROM information_schema.processlist"
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--source include/stop_slave.inc
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--source include/start_slave.inc
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--echo "Wait_for dump_thread_signal"
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SET DEBUG_SYNC='now WAIT_FOR dump_thread_signal';
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SET DEBUG_SYNC='show_binlogs_after_lock_log_before_lock_index SIGNAL parked1 WAIT_FOR go';
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--send SHOW BINARY LOGS
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echo "Wait_for parked1";
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SET DEBUG_SYNC='now WAIT_FOR parked1';
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SET DEBUG_SYNC='purge_logs_after_lock_index_before_thread_count SIGNAL parked2 WAIT_FOR go';
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--send PURGE BINARY LOGS BEFORE '9999-12-31'
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echo "Wait_for parked2";
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SET DEBUG_SYNC='now WAIT_FOR parked2';
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SET DEBUG_SYNC='processlist_after_LOCK_thd_count_before_LOCK_thd_data SIGNAL parked3 WAIT_FOR go';
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--let $query=SHOW PROCESSLIST
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--let $query=SELECT * FROM information_schema.processlist
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echo "Wait_for parked3";
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SET DEBUG_SYNC='now WAIT_FOR parked3';
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SET DEBUG_SYNC='now SIGNAL go';
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# Output of each command vary depends on other tests ran in suite(output vary
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# in Pb2 runs), so lets ignore output. Anyways, we are interested in seeing
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# that there is no deadlock.
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SET DEBUG_SYNC='RESET';
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SET GLOBAL DEBUG=@save_debug;
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source include/rpl_end.inc;
added
removed
mysql-test/suite/rpl/t/rpl_4threads_deadlock.test
