8a86df37ef
A 3-thread deadlock has been frequently observed when using innodb_change_buffering!=none and innodb_file_per_table=0: (1) ibuf_merge_or_delete_for_page() holding an exclusive latch on the block and waiting for an exclusive tablespace latch in fseg_page_is_allocated() (2) btr_free_but_not_root() in fseg_free_step() waiting for an exclusive tablespace latch (3) fsp_alloc_free_page() holding the exclusive tablespace latch and waiting for a latch on the block, which it is reallocating for something else While this was reproduced using innodb_file_per_table=0, this hang should be theoretically possible in .ibd files as well, when the recovery or cleanup of a failed DROP INDEX or ADD INDEX is executing concurrently with something that involves page allocation. ibuf_merge_or_delete_for_page(): Avoid invoking fseg_page_is_allocated() when block==nullptr. The call was redundant in this case, and it could cause deadlocks due to latching order violation. ibuf_read_merge_pages(): Acquire an exclusive tablespace latch before invoking buf_page_get_gen(), which may cause fseg_page_is_allocated() to be invoked in ibuf_merge_or_delete_for_page(). Note: This will not fix all latching order violations in this area! Deadlocks involving ibuf_merge_or_delete_for_page(block!=nullptr) are still possible if the caller is not acquiring an exclusive tablespace latch upfront. This would be the case in any read operation that involves a change buffer merge, such as SELECT, CHECK TABLE, or any DML operation that cannot be buffered in the change buffer.
Code status:
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MariaDB: The open source relational database
MariaDB was designed as a drop-in replacement of MySQL(R) with more features, new storage engines, fewer bugs, and better performance.
MariaDB is brought to you by the MariaDB Foundation and the MariaDB Corporation. Please read the CREDITS file for details about the MariaDB Foundation, and who is developing MariaDB.
MariaDB is developed by many of the original developers of MySQL who now work for the MariaDB Corporation, the MariaDB Foundation and by many people in the community.
MySQL, which is the base of MariaDB, is a product and trademark of Oracle Corporation, Inc. For a list of developers and other contributors, see the Credits appendix. You can also run 'SHOW authors' to get a list of active contributors.
A description of the MariaDB project and a manual can be found at:
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/
Help
More help is available from the Maria Discuss mailing list https://launchpad.net/~maria-discuss, MariaDB's Zulip instance, https://mariadb.zulipchat.com/
Live QA for beginner contributors
MariaDB has a dedicated time each week when we answer new contributor questions live on Zulip. From 8:00 to 10:00 UTC on Mondays, and 10:00 to 12:00 UTC on Thursdays, anyone can ask any questions they’d like, and a live developer will be available to assist.
New contributors can ask questions any time, but we will provide immediate feedback during that interval.
Licensing
NOTE:
MariaDB is specifically available only under version 2 of the GNU General Public License (GPLv2). (I.e. Without the "any later version" clause.) This is inherited from MySQL. Please see the README file in the MySQL distribution for more information.
License information can be found in the COPYING file. Third party license information can be found in the THIRDPARTY file.
Bug Reports
Bug and/or error reports regarding MariaDB should be submitted at: https://jira.mariadb.org
For reporting security vulnerabilities see: https://mariadb.org/about/security-policy/
The code for MariaDB, including all revision history, can be found at: https://github.com/MariaDB/server