The attached patch provides add-ins with the means to register for
shared memory and LWLocks. This greatly improves the ease with which
shared memory may be used from add-ins, while keeping the accounting and
management for that shared memory separate.
Specifically it adds named add-in shared memory contexts. From these,
memory can be allocated without affecting the memory available in other
contexts.
Usage is as follows:
from add-in functions called from preload_libraries, you may call
RegisterAddinContext(const * name, size_t size)
to register a new (logical) shared memory segment.
and
RegisterAddinLWLock(LWLockid *lock_ptr);
to request that a LWLock be allocated, placed into *lock_ptr.
The actual creation of the shared memory segment and lwlocks is
performed later as part of shared memory initialisation.
To allocate shared memory from a named context you would use
ShmemAllocFromContext(size_t size, const char *name);
To reset a shared memory context back to its original unused state (from
which new allocations may be performed), you may use
ShmemResetContext(const char *name);
This works for me (for Veil) and make check runs fine.
I have not included any documentation updates in the patch as I'm not
sure where such API changes should be documented.
All comments, questions and suggestions are welcomed.
__
Marc
