Issue: ------ The actual order of acquisition of the IBUF pessimistic insert mutex (SYNC_IBUF_PESS_INSERT_MUTEX) and IBUF header page latch (SYNC_IBUF_HEADER) w.r.t space latch (SYNC_FSP) differs from the order defined in sync0types.h. It was not discovered earlier as the path to ibuf_remove_free_page was not covered by the mtr test. Ideal order and one defined in sync0types.h is as follows. SYNC_IBUF_HEADER -> SYNC_IBUF_PESS_INSERT_MUTEX -> SYNC_FSP In ibuf_remove_free_page, we acquire space latch earlier and we have the order as follows resulting in the assert with innodb_sync_debug=on. SYNC_FSP -> SYNC_IBUF_HEADER -> SYNC_IBUF_PESS_INSERT_MUTEX Fix: --- We do maintain this order in other places and there doesn't seem to be any real issue here. To reduce impact in GA versions, we avoid doing extensive changes in mutex ordering to match the current SYNC_IBUF_PESS_INSERT_MUTEX order. Instead we relax the ordering check for IBUF pessimistic insert mutex using SYNC_NO_ORDER_CHECK.
Code status:
MariaDB: The innovative open source database
MariaDB was designed as a drop-in replacement of MySQL(R) with more features, new storage engines, fewer bugs, and better performance.
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https://mariadb.com/kb/en/mariadb-vs-mysql-features/
https://mariadb.com/kb/en/mariadb-versus-mysql-compatibility/
https://mariadb.com/kb/en/new-and-old-releases/
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