Refactor EXEC_BACKEND code so that postmaster child processes reattach

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

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
*

View File

@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.440 2004/11/17 08:30:09 neilc Exp $
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.441 2004/12/29 21:36:03 tgl Exp $
*
* NOTES
*
@ -1584,10 +1584,8 @@ processCancelRequest(Port *port, void *pkt)
int backendPID;
long cancelAuthCode;
Backend *bp;
#ifndef EXEC_BACKEND
Dlelem *curr;
#else
int i;
#endif
@ -3152,10 +3150,31 @@ SubPostmasterMain(int argc, char *argv[])
MyProcPid = getpid(); /* reset MyProcPid */
/* Read in file-based context */
/* In EXEC_BACKEND case we will not have inherited these settings */
IsPostmasterEnvironment = true;
whereToSendOutput = None;
/* Setup essential subsystems (to ensure elog() behaves sanely) */
MemoryContextInit();
InitializeGUCOptions();
/* Read in the variables file */
memset(&port, 0, sizeof(Port));
read_backend_variables(argv[2], &port);
/* Check we got appropriate args */
if (argc < 3)
elog(FATAL, "invalid subpostmaster invocation");
/*
* If appropriate, physically re-attach to shared memory segment.
* We want to do this before going any further to ensure that we
* can attach at the same address the postmaster used.
*/
if (strcmp(argv[1], "-forkbackend") == 0 ||
strcmp(argv[1], "-forkboot") == 0)
PGSharedMemoryReAttach();
/*
* Start our win32 signal implementation. This has to be done
* after we read the backend variables, because we need to pick
@ -3166,19 +3185,9 @@ SubPostmasterMain(int argc, char *argv[])
#endif
/* In EXEC_BACKEND case we will not have inherited these settings */
IsPostmasterEnvironment = true;
whereToSendOutput = None;
pqinitmask();
PG_SETMASK(&BlockSig);
/* Setup essential subsystems */
MemoryContextInit();
InitializeGUCOptions();
/* Check we got appropriate args */
if (argc < 3)
elog(FATAL, "invalid subpostmaster invocation");
/* Read in remaining GUC variables */
read_nondefault_variables();
@ -3187,7 +3196,7 @@ SubPostmasterMain(int argc, char *argv[])
{
/* BackendRun will close sockets */
/* Attach process to shared segments */
/* Attach process to shared data structures */
CreateSharedMemoryAndSemaphores(false, MaxBackends, 0);
#ifdef USE_SSL
@ -3208,7 +3217,7 @@ SubPostmasterMain(int argc, char *argv[])
/* Close the postmaster's sockets */
ClosePostmasterPorts(false);
/* Attach process to shared segments */
/* Attach process to shared data structures */
CreateSharedMemoryAndSemaphores(false, MaxBackends, 0);
BootstrapMain(argc - 2, argv + 2);
@ -3259,6 +3268,7 @@ SubPostmasterMain(int argc, char *argv[])
return 1; /* shouldn't get here */
}
#endif /* EXEC_BACKEND */
@ -3767,10 +3777,11 @@ read_inheritable_socket(SOCKET *dest, InheritableSocket *src)
static void
read_backend_variables(char *id, Port *port)
{
BackendParameters param;
#ifndef WIN32
/* Non-win32 implementation reads from file */
FILE *fp;
BackendParameters param;
/* Open file */
fp = AllocateFile(id, PG_BINARY_R);
@ -3796,25 +3807,23 @@ read_backend_variables(char *id, Port *port)
id, strerror(errno));
exit(1);
}
restore_backend_variables(&param, port);
#else
/* Win32 version uses mapped file */
HANDLE paramHandle;
BackendParameters *param;
BackendParameters *paramp;
paramHandle = (HANDLE)atol(id);
param = MapViewOfFile(paramHandle, FILE_MAP_READ, 0, 0, 0);
if (!param)
paramp = MapViewOfFile(paramHandle, FILE_MAP_READ, 0, 0, 0);
if (!paramp)
{
write_stderr("could not map view of backend variables: error code %d\n",
(int) GetLastError());
exit(1);
}
restore_backend_variables(param, port);
memcpy(&param, paramp, sizeof(BackendParameters));
if (!UnmapViewOfFile(param))
if (!UnmapViewOfFile(paramp))
{
write_stderr("could not unmap view of backend variables: error code %d\n",
(int) GetLastError());
@ -3828,6 +3837,8 @@ read_backend_variables(char *id, Port *port)
exit(1);
}
#endif
restore_backend_variables(&param, port);
}
/* Restore critical backend variables from the BackendParameters struct */
@ -3930,6 +3941,7 @@ ShmemBackendArrayRemove(pid_t pid)
(errmsg_internal("could not find backend entry with pid %d",
(int) pid)));
}
#endif /* EXEC_BACKEND */

View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.113 2004/09/16 16:58:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/file/fd.c,v 1.114 2004/12/29 21:36:05 tgl Exp $
*
* NOTES:
*
@ -228,6 +228,7 @@ static File fileNameOpenFile(FileName fileName, int fileFlags, int fileMode);
static char *filepath(const char *filename);
static void AtProcExit_Files(int code, Datum arg);
static void CleanupTempFiles(bool isProcExit);
static void RemovePgTempFilesInDir(const char *tmpdirname);
/*
@ -1482,59 +1483,83 @@ RemovePgTempFiles(void)
{
char db_path[MAXPGPATH];
char temp_path[MAXPGPATH];
char rm_path[MAXPGPATH];
DIR *db_dir;
DIR *temp_dir;
struct dirent *db_de;
struct dirent *temp_de;
/*
* Cycle through pg_tempfiles for all databases and remove old temp
* files.
* Cycle through pgsql_tmp directories for all databases and remove old
* temp files.
*/
snprintf(db_path, sizeof(db_path), "%s/base", DataDir);
if ((db_dir = AllocateDir(db_path)) != NULL)
db_dir = AllocateDir(db_path);
if (db_dir == NULL)
{
while ((db_de = readdir(db_dir)) != NULL)
{
if (strcmp(db_de->d_name, ".") == 0
#ifndef EXEC_BACKEND
/* no PG_TEMP_FILES_DIR in DataDir in non EXEC_BACKEND case */
|| strcmp(db_de->d_name, "..") == 0
#endif
)
continue;
snprintf(temp_path, sizeof(temp_path),
"%s/%s/%s",
db_path, db_de->d_name,
PG_TEMP_FILES_DIR);
if ((temp_dir = AllocateDir(temp_path)) != NULL)
{
while ((temp_de = readdir(temp_dir)) != NULL)
{
if (strcmp(temp_de->d_name, ".") == 0 ||
strcmp(temp_de->d_name, "..") == 0)
continue;
snprintf(rm_path, sizeof(temp_path),
"%s/%s/%s/%s",
db_path, db_de->d_name,
PG_TEMP_FILES_DIR,
temp_de->d_name);
if (strncmp(temp_de->d_name,
PG_TEMP_FILE_PREFIX,
strlen(PG_TEMP_FILE_PREFIX)) == 0)
unlink(rm_path);
else
elog(LOG,
"unexpected file found in temporary-files directory: \"%s\"",
rm_path);
}
FreeDir(temp_dir);
}
}
FreeDir(db_dir);
/* this really should not happen */
elog(LOG, "could not open directory \"%s\": %m", db_path);
return;
}
while ((db_de = readdir(db_dir)) != NULL)
{
if (strcmp(db_de->d_name, ".") == 0 ||
strcmp(db_de->d_name, "..") == 0)
continue;
snprintf(temp_path, sizeof(temp_path), "%s/%s/%s",
db_path, db_de->d_name, PG_TEMP_FILES_DIR);
RemovePgTempFilesInDir(temp_path);
}
FreeDir(db_dir);
/*
* In EXEC_BACKEND case there is a pgsql_tmp directory at the top
* level of DataDir as well.
*/
#ifdef EXEC_BACKEND
snprintf(temp_path, sizeof(temp_path), "%s/%s",
DataDir, PG_TEMP_FILES_DIR);
RemovePgTempFilesInDir(temp_path);
#endif
}
/* Process one pgsql_tmp directory for RemovePgTempFiles */
static void
RemovePgTempFilesInDir(const char *tmpdirname)
{
DIR *temp_dir;
struct dirent *temp_de;
char rm_path[MAXPGPATH];
temp_dir = AllocateDir(tmpdirname);
if (temp_dir == NULL)
{
/* anything except ENOENT is fishy */
if (errno != ENOENT)
elog(LOG,
"could not open temporary-files directory \"%s\": %m",
tmpdirname);
return;
}
while ((temp_de = readdir(temp_dir)) != NULL)
{
if (strcmp(temp_de->d_name, ".") == 0 ||
strcmp(temp_de->d_name, "..") == 0)
continue;
snprintf(rm_path, sizeof(rm_path), "%s/%s",
tmpdirname, temp_de->d_name);
if (strncmp(temp_de->d_name,
PG_TEMP_FILE_PREFIX,
strlen(PG_TEMP_FILE_PREFIX)) == 0)
unlink(rm_path); /* note we ignore any error */
else
elog(LOG,
"unexpected file found in temporary-files directory: \"%s\"",
rm_path);
}
FreeDir(temp_dir);
}

View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.72 2004/09/29 15:15:55 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/ipci.c,v 1.73 2004/12/29 21:36:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -19,6 +19,7 @@
#include "access/xlog.h"
#include "miscadmin.h"
#include "postmaster/bgwriter.h"
#include "postmaster/postmaster.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/ipc.h"
@ -37,14 +38,15 @@
* Creates and initializes shared memory and semaphores.
*
* This is called by the postmaster or by a standalone backend.
* It is also called by a backend forked from the postmaster under
* the EXEC_BACKEND case. (In the non EXEC_BACKEND case, backends
* start life already attached to shared memory.) The initialization
* functions are set up to simply "attach" to pre-existing shared memory
* structures in the latter case. We have to do that in order to
* initialize pointers in local memory that reference the shared structures.
* (In the non EXEC_BACKEND case, these pointer values are inherited via
* fork() from the postmaster.)
* It is also called by a backend forked from the postmaster in the
* EXEC_BACKEND case. In the latter case, the shared memory segment
* already exists and has been physically attached to, but we have to
* initialize pointers in local memory that reference the shared structures,
* because we didn't inherit the correct pointer values from the postmaster
* as we do in the fork() scenario. The easiest way to do that is to run
* through the same code as before. (Note that the called routines mostly
* check IsUnderPostmaster, rather than EXEC_BACKEND, to detect this case.
* This is a bit code-wasteful and could be cleaned up.)
*
* If "makePrivate" is true then we only need private memory, not shared
* memory. This is true for a standalone backend, false for a postmaster.
@ -101,14 +103,16 @@ CreateSharedMemoryAndSemaphores(bool makePrivate,
else
{
/*
* Attach to the shmem segment. (this should only ever be reached
* by EXEC_BACKEND code, and only then with makePrivate == false)
* We are reattaching to an existing shared memory segment.
* This should only be reached in the EXEC_BACKEND case, and
* even then only with makePrivate == false.
*/
#ifdef EXEC_BACKEND
Assert(!makePrivate);
seghdr = PGSharedMemoryCreate(-1, makePrivate, 0);
Assert(UsedShmemSegAddr != NULL);
seghdr = UsedShmemSegAddr;
#else
Assert(false);
elog(PANIC, "should be attached to shared memory already");
#endif
}

View File

@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/postmaster/postmaster.h,v 1.7 2004/08/29 05:06:58 momjian Exp $
* $PostgreSQL: pgsql/src/include/postmaster/postmaster.h,v 1.8 2004/12/29 21:36:08 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -41,6 +41,9 @@ extern void ClosePostmasterPorts(bool am_syslogger);
#ifdef EXEC_BACKEND
extern pid_t postmaster_forkexec(int argc, char *argv[]);
extern int SubPostmasterMain(int argc, char *argv[]);
extern size_t ShmemBackendArraySize(void);
extern void ShmemBackendArrayAllocation(void);
#endif
#endif /* _POSTMASTER_H */

View File

@ -11,7 +11,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/ipc.h,v 1.68 2004/08/29 05:06:58 momjian Exp $
* $PostgreSQL: pgsql/src/include/storage/ipc.h,v 1.69 2004/12/29 21:36:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -33,10 +33,4 @@ extern void CreateSharedMemoryAndSemaphores(bool makePrivate,
int maxBackends,
int port);
#ifdef EXEC_BACKEND
/* postmaster.c */
extern size_t ShmemBackendArraySize(void);
extern void ShmemBackendArrayAllocation(void);
#endif
#endif /* IPC_H */

View File

@ -17,7 +17,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/pg_shmem.h,v 1.12 2004/11/09 21:30:18 tgl Exp $
* $PostgreSQL: pgsql/src/include/storage/pg_shmem.h,v 1.13 2004/12/29 21:36:09 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -41,6 +41,8 @@ typedef struct PGShmemHeader /* standard header for all Postgres shmem */
#ifdef EXEC_BACKEND
extern unsigned long UsedShmemSegID;
extern void *UsedShmemSegAddr;
extern void PGSharedMemoryReAttach(void);
#endif
extern PGShmemHeader *PGSharedMemoryCreate(uint32 size, bool makePrivate,