database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-27 12:41:57 +03:00
Code Activity

Refactor EXEC_BACKEND code so that postmaster child processes reattach

Browse Source 
to shared memory as soon as possible, ie, right after read_backend_variables.
The effective difference from the original code is that this happens
before instead of after read_nondefault_variables(), which loads GUC
information and is apparently capable of expanding the backend's memory
allocation more than you'd think it should.  This should fix the
failure-to-attach-to-shared-memory reports we've been seeing on Windows.
Also clean up a few bits of unnecessarily grotty EXEC_BACKEND code.
This commit is contained in:
Tom Lane
2004-12-29 21:36:09 +00:00
parent e14018dc5e
commit eee5abce46
7 changed files with 179 additions and 124 deletions
Download Patch File Download Diff File Expand all files Collapse all files

75
src/backend/port/sysv_shmem.c
View File

@ -10,7 +10,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/port/sysv_shmem.c,v 1.40 2004/11/09 21:30:13 tgl Exp $
* $PostgreSQL: pgsql/src/backend/port/sysv_shmem.c,v 1.41 2004/12/29 21:35:58 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -142,11 +142,7 @@ InternalIpcMemoryCreate(IpcMemoryKey memKey, uint32 size)
on_shmem_exit(IpcMemoryDelete, Int32GetDatum(shmid));
/* OK, should be able to attach to the segment */
#ifdef EXEC_BACKEND
memAddress = shmat(shmid, UsedShmemSegAddr, PG_SHMAT_FLAGS);
#else
memAddress = shmat(shmid, NULL, PG_SHMAT_FLAGS);
#endif
if (memAddress == (void *) -1)
elog(FATAL, "shmat(id=%d) failed: %m", shmid);
@ -279,7 +275,7 @@ PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2)
*
* Create a shared memory segment of the given size and initialize its
* standard header. Also, register an on_shmem_exit callback to release
* the storage. For an exec'ed backend, it just attaches.
* the storage.
*
* Dead Postgres segments are recycled if found, but we do not fail upon
* collision with non-Postgres shmem segments. The idea here is to detect and
@ -303,30 +299,6 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
struct stat statbuf;
#endif
#ifdef EXEC_BACKEND
/* If Exec case, just attach and return the pointer */
if (UsedShmemSegAddr != NULL && !makePrivate && IsUnderPostmaster)
{
void *origUsedShmemSegAddr = UsedShmemSegAddr;
#ifdef __CYGWIN__
/* cygipc (currently) appears to not detach on exec. */
PGSharedMemoryDetach();
UsedShmemSegAddr = origUsedShmemSegAddr;
#endif
elog(DEBUG3, "Attaching to %p", UsedShmemSegAddr);
hdr = PGSharedMemoryAttach((IpcMemoryKey) UsedShmemSegID, &shmid);
if (hdr == NULL)
elog(FATAL, "could not attach to proper memory at fixed address: shmget(key=%d, addr=%p) failed: %m",
(int) UsedShmemSegID, UsedShmemSegAddr);
if (hdr != origUsedShmemSegAddr)
elog(FATAL, "attaching to shared mem returned unexpected address (got %p, expected %p)",
hdr, UsedShmemSegAddr);
UsedShmemSegAddr = hdr;
return hdr;
}
#endif
/* Room for a header? */
Assert(size > MAXALIGN(sizeof(PGShmemHeader)));
@ -424,6 +396,49 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port)
return hdr;
}
#ifdef EXEC_BACKEND
/*
* PGSharedMemoryReAttach
*
* Re-attach to an already existing shared memory segment. In the non
* EXEC_BACKEND case this is not used, because 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);
UsedShmemSegAddr = hdr; /* probably redundant */
}
#endif /* EXEC_BACKEND */
/*
* PGSharedMemoryDetach
*