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Simplify Windows implementation of latches. There's no need to keep a

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dynamic pool of event handles, we can permanently assign one for each
shared latch. Thanks to that, we no longer need a separate shared memory
block for latches, and we don't need to know in advance how many shared
latches there is, so you no longer need to remember to update
NumSharedLatches when you introduce a new latch to the system.
This commit is contained in:
Heikki Linnakangas
2010-09-15 10:06:21 +00:00
parent 1eab7a560d
commit 236b6bc29e
4 changed files with 39 additions and 153 deletions
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31
src/backend/port/unix_latch.c
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@ -77,7 +77,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/port/unix_latch.c,v 1.3 2010/09/13 18:01:20 heikki Exp $
* $PostgreSQL: pgsql/src/backend/port/unix_latch.c,v 1.4 2010/09/15 10:06:21 heikki Exp $
*
*-------------------------------------------------------------------------
*/
@ -129,8 +129,10 @@ InitLatch(volatile Latch *latch)
* is initially owned by no-one, use OwnLatch to associate it with the
* current process.
*
* NB: When you introduce a new shared latch, you must increase the shared
* latch count in NumSharedLatches in win32_latch.c!
* InitSharedLatch needs to be called in postmaster before forking child
* processes, usually right after allocating the shared memory block
* containing the latch with ShmemInitStruct. The Unix implementation
* doesn't actually require that, but the Windows one does.
*/
void
InitSharedLatch(volatile Latch *latch)
@ -322,29 +324,6 @@ ResetLatch(volatile Latch *latch)
latch->is_set = false;
}
/*
* LatchShmemSize
* Compute space needed for latch's shared memory
*
* Not needed for Unix implementation.
*/
Size
LatchShmemSize(void)
{
return 0;
}
/*
* LatchShmemInit
* Allocate and initialize shared memory needed for latches
*
* Not needed for Unix implementation.
*/
void
LatchShmemInit(void)
{
}
/*
* SetLatch uses SIGUSR1 to wake up the process waiting on the latch. Wake
* up WaitLatch.