/*
* PGSharedMemoryReAttach
*
* This is called during startup of a postmaster child process to re-attach to
* an already existing shared memory segment. This is needed only in the
* EXEC_BACKEND case; otherwise postmaster children inherit the shared memory
* segment attachment via fork().
*
* UsedShmemSegID and UsedShmemSegAddr are implicit parameters to this
* routine. The caller must have already restored them to the postmaster's
* values.
*/
void
PGSharedMemoryReAttach(void)
{
IpcMemoryId shmid;
void *hdr;
void *origUsedShmemSegAddr = UsedShmemSegAddr;
Assert(UsedShmemSegAddr != NULL);
Assert(IsUnderPostmaster);
#ifdef __CYGWIN__
/* cygipc (currently) appears to not detach on exec. */
PGSharedMemoryDetach();
UsedShmemSegAddr = origUsedShmemSegAddr;
#endif
elog(DEBUG3, "attaching to %p", UsedShmemSegAddr);
hdr = (void *) PGSharedMemoryAttach((IpcMemoryKey) UsedShmemSegID, &shmid);
if (hdr == NULL)
elog(FATAL, "could not reattach to shared memory (key=%d, addr=%p): %m",
(int) UsedShmemSegID, UsedShmemSegAddr);
if (hdr != origUsedShmemSegAddr)
elog(FATAL, "reattaching to shared memory returned unexpected address (got %p, expected %p)",
hdr, origUsedShmemSegAddr);
dsm_set_control_handle(((PGShmemHeader *) hdr)->dsm_control);
UsedShmemSegAddr = hdr; /* probably redundant */
}
/*
* PGSharedMemoryReAttach
*
* This is called during startup of a postmaster child process to re-attach to
* an already existing shared memory segment, using the handle inherited from
* the postmaster.
*
* UsedShmemSegID and UsedShmemSegAddr are implicit parameters to this
* routine. The caller must have already restored them to the postmaster's
* values.
*/
void
PGSharedMemoryReAttach(void)
{
PGShmemHeader *hdr;
void *origUsedShmemSegAddr = UsedShmemSegAddr;
Assert(UsedShmemSegAddr != NULL);
Assert(IsUnderPostmaster);
/*
* Release memory region reservation that was made by the postmaster
*/
if (VirtualFree(UsedShmemSegAddr, 0, MEM_RELEASE) == 0)
elog(FATAL, "failed to release reserved memory region (addr=%p): error code %lu",
UsedShmemSegAddr, GetLastError());
hdr = (PGShmemHeader *) MapViewOfFileEx(UsedShmemSegID, FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, 0, UsedShmemSegAddr);
if (!hdr)
elog(FATAL, "could not reattach to shared memory (key=%p, addr=%p): error code %lu",
UsedShmemSegID, UsedShmemSegAddr, GetLastError());
if (hdr != origUsedShmemSegAddr)
elog(FATAL, "reattaching to shared memory returned unexpected address (got %p, expected %p)",
hdr, origUsedShmemSegAddr);
if (hdr->magic != PGShmemMagic)
elog(FATAL, "reattaching to shared memory returned non-PostgreSQL memory");
dsm_set_control_handle(hdr->dsm_control);
UsedShmemSegAddr = hdr; /* probably redundant */
}