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  1. MariaDB Server
  2. MDEV-15135

'show global status' can cause lock contention on LOCK_thread_count

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      calc_sum_of_all_status() holds the LOCK_thread_count mutex for the whole duration of its calculations, which can take a while when having many active connections, so blocking other threads waiting on the same mutex.

      In MySQL 5.7 this is fixed by taking copies of relevant THD object data first (while holding the LOCK_thread_count), and only then doing the actual calculations after releasing the mutex again.

      See MySQL bug #42930 and changeset 034c40f4baeff1a1d2dd637f6a1f2c2720a4d26f

      https://bugs.mysql.com/bug.php?id=42930

      https://github.com/mysql/mysql-server/commit/034c40f4baeff1a1d2dd637f6a1f2c2720a4d26f

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          blocks

          Bug - A problem which impairs or prevents the functions of the product. MDEV-13983 Mariadb becomes unresponsive

          • Major - Major loss of function.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-17251 SHOW STATUS unnecessary calls calc_sum_of_all_status

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-13983 Mariadb becomes unresponsive

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-20547 mysqld crashes: Semaphore wait has lasted > 60 seconds

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

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              wlad Vladislav Vaintroub
              hholzgra Hartmut Holzgraefe
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