Andrei Elkin c7e38076f3 MDEV-9510 Segmentation fault in binlog thread causes crash ...

With combination of --log-bin and Galera the server may crash
reporting two characteristic stacks:

  /usr/sbin/mysqld(_ZN13MYSQL_BIN_LOG13mark_xid_doneEmb+0xc7)[0x7f182a8e2cb7]
  /usr/sbin/mysqld(binlog_background_thread+0x2b5)[0x7f182a8e3275]

or

  /usr/sbin/mysqld(_ZN13MYSQL_BIN_LOG21do_checkpoint_requestEm+0x9d)[0x7ff395b2dafd]
  /usr/sbin/mysqld(_ZN13MYSQL_BIN_LOG20checkpoint_and_purgeEm+0x11)[0x7ff395b2db91]
  /usr/sbin/mysqld(_ZN13MYSQL_BIN_LOG16rotate_and_purgeEb+0xc2)[0x7ff395b300b2]

The reason of the failure appears to be non-matching decrements for
  `xid_count_per_binlog::xid_count`
which can occur when a transaction is executed having its connection issued
`SET @@sql_log_bin=0`. In such case the xid count is not incremented but
its decrements still runs to turn `binlog_xid_count_list` into improper state
which the following FLUSH BINARY LOGS exposes through the crash.

*Note_1*: the regression test reuses an existing galera.sql_log_bin
which does not run stably (even in its base form) by mtr with --log-bin.

*Note_2*: 10.0-galera branch is free of this issue having missed MDEV-7205
fixes.

2017-11-15 22:26:32 +02:00

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