3c0fd64fec
Split ProcSleep into two functions: JoinWaitQueue and ProcSleep. JoinWaitQueue is called while holding the partition lock, and inserts the current process to the wait queue, while ProcSleep() does the actual sleeping. ProcSleep() is now called without holding the partition lock, and it no longer re-acquires the partition lock before returning. That makes the wakeup a little cheaper. Once upon a time, re-acquiring the partition lock was needed to prevent a signal handler from longjmping out at a bad time, but these days our signal handlers just set flags, and longjmping can only happen at points where we explicitly run CHECK_FOR_INTERRUPTS(). If JoinWaitQueue detects an "early deadlock" before even joining the wait queue, it returns without changing the shared lock entry, leaving the cleanup of the shared lock entry to the caller. This makes the handling of an early deadlock the same as the dontWait=true case. One small user-visible side-effect of this refactoring is that we now only set the 'ps' title to say "waiting" when we actually enter the sleep, not when the lock is skipped because dontWait=true, or when a deadlock is detected early before entering the sleep. This eliminates the 'lockAwaited' global variable in proc.c, which was largely redundant with 'awaitedLock' in lock.c Note: Updating the local lock table is now the caller's responsibility. JoinWaitQueue and ProcSleep are now only responsible for modifying the shared state. Seems a little nicer that way. Based on Thomas Munro's earlier patch and observation that ProcSleep doesn't really need to re-acquire the partition lock. Reviewed-by: Maxim Orlov Discussion: https://www.postgresql.org/message-id/7c2090cd-a72a-4e34-afaa-6dd2ef31440e@iki.fi
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/.