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WaitLSNWakeup() removes each selected waiter from its heap and clears its inHeap flag before setting its latch. When such a waiter later calls deleteLSNWaiter(), it acquires WaitLSNLock exclusively only to discover that there is nothing left to remove. Waking many waiters can therefore make them serialize on the lock for no useful work. Check inHeap before acquiring WaitLSNLock. A lockless false value is conclusive because only the owning backend can change inHeap from false to true. A concurrent waker can only clear it. A stale true value falls through to the existing recheck under the lock. WaitLSNCleanup() performed the same lockless check before calling deleteLSNWaiter(). Drop it there, as it is now redundant. Author: Xuneng Zhou <xunengzhou@gmail.com> Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com> Discussion: https://postgr.es/m/CABPTF7UtW_cAa%3DQh4RDfKiUqu3pJJE22ai9tbWJVERbeRyssLw%40mail.gmail.com Backpatch-through: 19
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.