On Wed, 2006-07-12 at 02:18 -0300, I wrote: > I am trying to create an initialisation function that is called using > the preload_libraries option. > > The purpose of this is to set up shared memory for Veil, independant > of postgres' own shared memory. Simple init functions work fine, but > as soon as I place calls to ShemAlloc, or LWLockAssign, the server > startup simply halts.
To answer my own question, yes I am being unreasonable. Shared memory has not been set up at the time that process_preload_libraries is called. Since lwlocks are allocated from postgres shared memory, I cannot assign an lwlock from Veil's initialisation code. Instead, I can make the allocation of the lwlock the responsibility of the first session that uses a Veil function but I need a lock to prevent a race. My current thinking is to simply subvert one of the existing lwlocks while I assign my own. A better solution from my point of view would be to simply move the call to process_preload_libraries to a point after shared memory has been set up. Is there some reason this could not be done? On a related note, I can see no way to release Veil's shared memory segment when postgres is shut down. Perhaps I should be thinking about making the management of such shared memory segments something that postgres does on behalf of its add-ins, though that seems presumptious. I'd appreciate any suggestions, pointers, random thoughts, etc. __ Marc
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