Details
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Bug
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Status: Closed (View Workflow)
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Blocker
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Resolution: Fixed
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N/A
Description
In MDEV-27774, the log_sys.mutex and log_sys.flush_order_mutex were replaced with a shared log_sys.latch. This means that concurrently executing mtr_t::commit() may insert records to the buf_pool.flush_list roughly concurrently. Each insertion is still protected by buf_pool.flush_list_mutex.
In buf_pool_t::insert_into_flush_list() we attempted to compensate for this by not unconditionally inserting blocks first in buf_pool.flush_list but by searching for an appropriate insert position. This compensation does not appear to be working at all times. With the following command, I was able to reproduce a crash on my system:
./mtr --parallel=auto --repeat=100 encryption.innodb_encryption_filekeys{,,,,}{,,,}
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10.8 8251a9fb93075a72074bd7fd10faee5165014b7f |
encryption.innodb_encryption_filekeys 'cbc,innodb' w1 [ 26 fail ]
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Test ended at 2022-02-17 10:28:31
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CURRENT_TEST: encryption.innodb_encryption_filekeys
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Server [mysqld.1 - pid: 488142, winpid: 488142, exit: 256] failed during test run
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Server log from this test:
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----------SERVER LOG START-----------
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2022-02-17 10:28:30 104 [Note] InnoDB: Creating #1 encryption thread id 140526397404736 total threads 4.
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2022-02-17 10:28:30 104 [Note] InnoDB: Creating #2 encryption thread id 140526389012032 total threads 4.
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2022-02-17 10:28:30 104 [Note] InnoDB: Creating #3 encryption thread id 140526405797440 total threads 4.
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2022-02-17 10:28:30 104 [Note] InnoDB: Creating #4 encryption thread id 140526414190144 total threads 4.
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mariadbd: /mariadb/10.8/storage/innobase/buf/buf0flu.cc:2538: void buf_flush_validate_low(): Assertion `om == 1 || !bpage || __builtin_expect(recv_sys.recovery_on, (0)) || om >= bpage->oldest_modification()' failed.
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The assertion reports that buf_pool.flush_list is not ordered by buf_page_t::oldest_modification(), like it must be.
The impact of this bug is that log checkpoints and thus crash recovery and backup may work incorrectly.
Attachments
Issue Links
- causes
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- Closed
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- is caused by
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- Closed
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- relates to
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MDEV-25113 Reduce effect of parallel background flush on select workload
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- Closed
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