Bruce Momjian wrote:
> Tom Lane wrote:
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > > In this way, no one ever has the rename file open while we are holding
> > > the locks, and we can loop without holding an exclusive lock on
> > > pg_shadow, and file writes remain in order.
> >
> > You're doing this where exactly, and are certain that you are holding no
> > locks why exactly? And if you aren't holding a lock, what prevents
> > concurrency bugs?
>
> Oh, for concurrency bugs, you make realfile.new while holding the
> exclusive lock, so someone could come in later and replace realfile.new
> while I am in the rename loop, but then I just install theirs instead.
>
> I could install someone who has just done the rename to realfile.new but
> not tried the rename from realfile.new to realfile, but that seems OK.
> They will just fine the file missing and fail on the rename, which is
> OK.
OK, here is a patch that I think handles rename. It does the rename to
a secondary file while holding the lock, then releases the lock and does
a rename to the active file. I enabled this for Win32 and Cygwin, which
has the same file system behavior.
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
Index: src/backend/commands/user.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/commands/user.c,v
retrieving revision 1.133
diff -c -c -r1.133 user.c
*** src/backend/commands/user.c 26 Jan 2004 22:35:32 -0000 1.133
--- src/backend/commands/user.c 27 Jan 2004 03:46:00 -0000
***************
*** 139,145 ****
bufsize = strlen(filename) + 12;
tempname = (char *) palloc(bufsize);
snprintf(tempname, bufsize, "%s.%d", filename, MyProcPid);
!
oumask = umask((mode_t) 077);
fp = AllocateFile(tempname, "w");
umask(oumask);
--- 139,149 ----
bufsize = strlen(filename) + 12;
tempname = (char *) palloc(bufsize);
snprintf(tempname, bufsize, "%s.%d", filename, MyProcPid);
! #if defined(WIN32) || defined(CYGWIN)
! filename = repalloc(filename, strlen(filename) + 1 + strlen(".new");
! strcat(filename, ".new");
! #endif
!
oumask = umask((mode_t) 077);
fp = AllocateFile(tempname, "w");
umask(oumask);
***************
*** 286,291 ****
--- 290,299 ----
bufsize = strlen(filename) + 12;
tempname = (char *) palloc(bufsize);
snprintf(tempname, bufsize, "%s.%d", filename, MyProcPid);
+ #if defined(WIN32) || defined(CYGWIN)
+ filename = repalloc(filename, strlen(filename) + 1 + strlen(".new");
+ strcat(filename, ".new");
+ #endif
oumask = umask((mode_t) 077);
fp = AllocateFile(tempname, "w");
***************
*** 457,462 ****
--- 465,482 ----
user_file_update_needed = false;
write_user_file(urel);
heap_close(urel, NoLock);
+ #if defined(WIN32) || defined(CYGWIN)
+ {
+ /* Rename active file while not holding an exclusive lock */
+ char *filename = user_getfilename(), *filename_new;
+
+ filename_new = palloc(strlen(filename) + 1 + strlen(".new")));
+ sprintf(filename_new, "%s.new", filename);
+ rename(filename_new, filename);
+ pfree(filename);
+ pfree(filename_new);
+ }
+ #endif
}
if (group_file_update_needed)
***************
*** 464,469 ****
--- 484,501 ----
group_file_update_needed = false;
write_group_file(grel);
heap_close(grel, NoLock);
+ #if defined(WIN32) || defined(CYGWIN)
+ {
+ /* Rename active file while not holding an exclusive lock */
+ char *filename = group_getfilename(), *filename_new;
+
+ filename_new = palloc(strlen(filename) + 1 + strlen(".new")));
+ sprintf(filename_new, "%s.new", filename);
+ rename(filename_new, filename);
+ pfree(filename);
+ pfree(filename_new);
+ }
+ #endif
}
/*
Index: src/backend/utils/cache/relcache.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/cache/relcache.c,v
retrieving revision 1.195
diff -c -c -r1.195 relcache.c
*** src/backend/utils/cache/relcache.c 26 Jan 2004 22:35:32 -0000 1.195
--- src/backend/utils/cache/relcache.c 27 Jan 2004 03:46:04 -0000
***************
*** 3358,3390 ****
/*
* OK, rename the temp file to its final name, deleting any
* previously-existing init file.
- *
- * Note: a failure here is possible under Cygwin, if some other
- * backend is holding open an unlinked-but-not-yet-gone init file.
- * So treat this as a noncritical failure.
*/
! if (rename(tempfilename, finalfilename) < 0)
{
! ereport(WARNING,
! (errcode_for_file_access(),
! errmsg("could not rename relation-cache initialization file \"%s\" to \"%s\": %m",
! tempfilename, finalfilename),
! errdetail("Continuing anyway, but there's something wrong.")));
!
! /*
! * If we fail, try to clean up the useless temp file; don't
! * bother to complain if this fails too.
! */
! unlink(tempfilename);
}
}
else
{
/* Delete the already-obsolete temp file */
unlink(tempfilename);
}
-
- LWLockRelease(RelCacheInitLock);
}
/*
--- 3358,3385 ----
/*
* OK, rename the temp file to its final name, deleting any
* previously-existing init file.
*/
! #if defined(WIN32) || defined(CYGWIN)
! rename(tempfilename, finalfilename);
! LWLockRelease(RelCacheInitLock);
! #else
{
! char finalfilename_new[MAXPGPATH];
!
! snprintf(finalfilename_new, sizeof(finalfilename_new), "%s.new", finalfilename);
! rename(tempfilename, finalfilename_new);
! LWLockRelease(RelCacheInitLock);
! /* Rename to active file after lock is released */
! rename(finalfilename_new, finalfilename);
}
+ #endif
}
else
{
/* Delete the already-obsolete temp file */
unlink(tempfilename);
+ LWLockRelease(RelCacheInitLock);
}
}
/*
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/backend/utils/misc/guc.c,v
retrieving revision 1.181
diff -c -c -r1.181 guc.c
*** src/backend/utils/misc/guc.c 26 Jan 2004 22:35:32 -0000 1.181
--- src/backend/utils/misc/guc.c 27 Jan 2004 03:46:07 -0000
***************
*** 3981,3987 ****
return;
}
! /* Put new file in place, this could delay on Win32 */
rename(new_filename, filename);
free(new_filename);
free(filename);
--- 3981,3990 ----
return;
}
! /*
! * Put new file in place. This could delay on Win32, but we don't hold
! * any exclusive locks.
! */
rename(new_filename, filename);
free(new_filename);
free(filename);
Index: src/include/port.h
===================================================================
RCS file: /cvsroot/pgsql-server/src/include/port.h,v
retrieving revision 1.15
diff -c -c -r1.15 port.h
*** src/include/port.h 29 Nov 2003 22:40:53 -0000 1.15
--- src/include/port.h 27 Jan 2004 03:46:07 -0000
***************
*** 30,40 ****
extern off_t ftello(FILE *stream);
#endif
! #ifdef WIN32
/*
* Win32 doesn't have reliable rename/unlink during concurrent access
*/
- #ifndef FRONTEND
extern int pgrename(const char *from, const char *to);
extern int pgunlink(const char *path);
--- 30,39 ----
extern off_t ftello(FILE *stream);
#endif
! #if !defined(FRONTEND) && (defined(WIN32) || defined(CYGWIN))
/*
* Win32 doesn't have reliable rename/unlink during concurrent access
*/
extern int pgrename(const char *from, const char *to);
extern int pgunlink(const char *path);
***************
*** 42,47 ****
--- 41,47 ----
#define unlink(path) pgunlink(path)
#endif
+ #ifdef WIN32
extern int copydir(char *fromdir, char *todir);
/* Last parameter not used */
Index: src/port/dirmod.c
===================================================================
RCS file: /cvsroot/pgsql-server/src/port/dirmod.c,v
retrieving revision 1.8
diff -c -c -r1.8 dirmod.c
*** src/port/dirmod.c 29 Nov 2003 19:52:13 -0000 1.8
--- src/port/dirmod.c 27 Jan 2004 03:46:08 -0000
***************
*** 27,35 ****
--- 27,45 ----
{
int loops = 0;
+ #ifdef WIN32
while (!MoveFileEx(from, to, MOVEFILE_REPLACE_EXISTING))
+ #endif
+ #ifdef CYGWIN
+ while (rename(from, to) < 0)
+ #endif
{
+ #ifdef WIN32
if (GetLastError() != ERROR_ACCESS_DENIED)
+ #endif
+ #ifdef CYGWIN
+ if (errno != EACCES)
+ #endif
/* set errno? */
return -1;
Sleep(100); /* ms */
