diff options
Diffstat (limited to 'src/backend/port/sysv_shmem.c')
| -rw-r--r-- | src/backend/port/sysv_shmem.c | 89 |
1 files changed, 55 insertions, 34 deletions
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c index c98aff5231..9454c3e92c 100644 --- a/src/backend/port/sysv_shmem.c +++ b/src/backend/port/sysv_shmem.c @@ -10,7 +10,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.8 2003/05/06 23:34:55 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/port/sysv_shmem.c,v 1.9 2003/05/08 14:49:03 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -39,9 +39,8 @@ typedef int IpcMemoryId; /* shared memory ID returned by shmget(2) */ #define IPCProtection (0600) /* access/modify by user only */ -#ifdef EXEC_BACKEND IpcMemoryKey UsedShmemSegID = 0; -#endif +void *UsedShmemSegAddr = NULL; static void *InternalIpcMemoryCreate(IpcMemoryKey memKey, uint32 size); static void IpcMemoryDetach(int status, Datum shmaddr); @@ -282,7 +281,7 @@ PrivateMemoryDelete(int status, Datum memaddr) * * 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. + * the storage. For an exec'ed backend, it just attaches. * * 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 @@ -302,11 +301,9 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port) /* Room for a header? */ Assert(size > MAXALIGN(sizeof(PGShmemHeader))); -#ifdef EXEC_BACKEND - if (UsedShmemSegID != 0) + if (ExecBackend && UsedShmemSegID != 0) NextShmemSegID = UsedShmemSegID; else -#endif NextShmemSegID = port * 1000 + 1; for (;;NextShmemSegID++) @@ -320,25 +317,39 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port) break; } - /* Try to create new segment */ - memAddress = InternalIpcMemoryCreate(NextShmemSegID, size); - if (memAddress) - break; /* successful create and attach */ + /* If attach to fixed address, only try once */ + if (ExecBackend && UsedShmemSegAddr != NULL && NextShmemSegID != UsedShmemSegID) + { + fprintf(stderr, "Unable to attach to memory at fixed address: shmget(key=%d, addr=%p) failed: %s\n", + (int) UsedShmemSegID, UsedShmemSegAddr, strerror(errno)); + proc_exit(1); + } + + if (!ExecBackend || UsedShmemSegAddr == NULL) + { + /* Try to create new segment */ + memAddress = InternalIpcMemoryCreate(NextShmemSegID, size); + if (memAddress) + break; /* successful create and attach */ + } /* See if it looks to be leftover from a dead Postgres process */ shmid = shmget(NextShmemSegID, sizeof(PGShmemHeader), 0); if (shmid < 0) continue; /* failed: must be some other app's */ -#if defined(solaris) && defined(__sparc__) /* use intimate shared memory on SPARC Solaris */ - memAddress = shmat(shmid, 0, SHM_SHARE_MMU); + memAddress = shmat(shmid, UsedShmemSegAddr, +#if defined(solaris) && defined(__sparc__) + SHM_SHARE_MMU #else - memAddress = shmat(shmid, 0, 0); + 0 #endif + ); if (memAddress == (void *) -1) continue; /* failed: must be some other app's */ + hdr = (PGShmemHeader *) memAddress; if (hdr->magic != PGShmemMagic) { @@ -346,14 +357,19 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port) continue; /* segment belongs to a non-Postgres app */ } + /* Successfully attached to shared memory, which is all we wanted */ + if (ExecBackend && UsedShmemSegAddr != NULL) + break; + + /* Check shared memory and possibly remove and recreate */ + /* - * If the creator PID is my own PID or does not belong to any - * extant process, it's safe to zap it. + * If I am not the creator and it belongs to an extant process, + * continue. */ if (hdr->creatorPID != getpid()) { - if (kill(hdr->creatorPID, 0) == 0 || - errno != ESRCH) + if (kill(hdr->creatorPID, 0) == 0 || errno != ESRCH) { shmdt(memAddress); continue; /* segment belongs to a live process */ @@ -385,26 +401,31 @@ PGSharedMemoryCreate(uint32 size, bool makePrivate, int port) */ } - /* - * OK, we created a new segment. Mark it as created by this process. - * The order of assignments here is critical so that another Postgres - * process can't see the header as valid but belonging to an invalid - * PID! - */ hdr = (PGShmemHeader *) memAddress; - hdr->creatorPID = getpid(); - hdr->magic = PGShmemMagic; - /* - * Initialize space allocation status for segment. - */ - hdr->totalsize = size; - hdr->freeoffset = MAXALIGN(sizeof(PGShmemHeader)); + if (!ExecBackend || makePrivate || UsedShmemSegAddr == NULL) + { + /* + * OK, we created a new segment. Mark it as created by this process. + * The order of assignments here is critical so that another Postgres + * process can't see the header as valid but belonging to an invalid + * PID! + */ + hdr->creatorPID = getpid(); + hdr->magic = PGShmemMagic; + + /* + * Initialize space allocation status for segment. + */ + hdr->totalsize = size; + hdr->freeoffset = MAXALIGN(sizeof(PGShmemHeader)); + } -#ifdef EXEC_BACKEND - if (!makePrivate && UsedShmemSegID == 0) + if (ExecBackend && !makePrivate && UsedShmemSegAddr == NULL) + { + UsedShmemSegAddr = memAddress; UsedShmemSegID = NextShmemSegID; -#endif + } return hdr; } |