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Commita7e5878

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Reserve the shared memory region during backend startup on Windows, so
that memory allocated by starting third party DLLs doesn't end upconflicting with it.Hopefully this solves the long-time issue with "could not reattachto shared memory" errors on Win32.Patch from Tsutomu Yamada and me, based on idea from Trevor Talbot.
1 parent5e22994 commita7e5878

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3 files changed

+85
-4
lines changed

3 files changed

+85
-4
lines changed

‎src/backend/port/win32_shmem.c

Lines changed: 60 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
77
*
88
* IDENTIFICATION
9-
* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.11 2009/06/11 14:49:00 momjian Exp $
9+
* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.12 2009/07/24 20:12:42 mha Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -18,6 +18,7 @@
1818

1919
unsigned longUsedShmemSegID=0;
2020
void*UsedShmemSegAddr=NULL;
21+
staticSizeUsedShmemSegSize=0;
2122

2223
staticvoidpgwin32_SharedMemoryDelete(intstatus,DatumshmId);
2324

@@ -233,6 +234,7 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port)
233234

234235
/* Save info for possible future use */
235236
UsedShmemSegAddr=memAddress;
237+
UsedShmemSegSize=size;
236238
UsedShmemSegID= (unsigned long)hmap2;
237239

238240
returnhdr;
@@ -257,6 +259,13 @@ PGSharedMemoryReAttach(void)
257259
Assert(UsedShmemSegAddr!=NULL);
258260
Assert(IsUnderPostmaster);
259261

262+
/*
263+
* Release memory region reservation that was made by the postmaster
264+
*/
265+
if (VirtualFree(UsedShmemSegAddr,0,MEM_RELEASE)==0)
266+
elog(FATAL,"failed to release reserved memory region (addr=%p): %lu",
267+
UsedShmemSegAddr,GetLastError());
268+
260269
hdr= (PGShmemHeader*)MapViewOfFileEx((HANDLE)UsedShmemSegID,FILE_MAP_READ |FILE_MAP_WRITE,0,0,0,UsedShmemSegAddr);
261270
if (!hdr)
262271
elog(FATAL,"could not reattach to shared memory (key=%d, addr=%p): %lu",
@@ -302,3 +311,53 @@ pgwin32_SharedMemoryDelete(int status, Datum shmId)
302311
if (!CloseHandle((HANDLE)DatumGetInt32(shmId)))
303312
elog(LOG,"could not close handle to shared memory: %lu",GetLastError());
304313
}
314+
315+
/*
316+
* pgwin32_ReserveSharedMemoryRegion(hChild)
317+
*
318+
* Reserve the memory region that will be used for shared memory in a child
319+
* process. It is called before the child process starts, to make sure the
320+
* memory is available.
321+
*
322+
* Once the child starts, DLLs loading in different order or threads getting
323+
* scheduled differently may allocate memory which can conflict with the
324+
* address space we need for our shared memory. By reserving the shared
325+
* memory region before the child starts, and freeing it only just before we
326+
* attempt to get access to the shared memory forces these allocations to
327+
* be given different address ranges that don't conflict.
328+
*
329+
* NOTE! This function executes in the postmaster, and should for this
330+
* reason not use elog(FATAL) since that would take down the postmaster.
331+
*/
332+
int
333+
pgwin32_ReserveSharedMemoryRegion(HANDLEhChild)
334+
{
335+
void*address;
336+
337+
Assert(UsedShmemSegAddr!=NULL);
338+
Assert(UsedShmemSegSize!=0);
339+
340+
address=VirtualAllocEx(hChild,UsedShmemSegAddr,UsedShmemSegSize,
341+
MEM_RESERVE,PAGE_READWRITE);
342+
if (address==NULL) {
343+
/* Don't use FATAL since we're running in the postmaster */
344+
elog(LOG,"could not reserve shared memory region (addr=%p) for child %lu: %lu",
345+
UsedShmemSegAddr,hChild,GetLastError());
346+
return false;
347+
}
348+
if (address!=UsedShmemSegAddr)
349+
{
350+
/*
351+
* Should never happen - in theory if allocation granularity causes strange
352+
* effects it could, so check just in case.
353+
*
354+
* Don't use FATAL since we're running in the postmaster.
355+
*/
356+
elog(LOG,"reserved shared memory region got incorrect address %p, expected %p",
357+
address,UsedShmemSegAddr);
358+
VirtualFreeEx(hChild,address,0,MEM_RELEASE);
359+
return false;
360+
}
361+
362+
return true;
363+
}

‎src/backend/postmaster/postmaster.c

Lines changed: 21 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,7 @@
3737
*
3838
*
3939
* IDENTIFICATION
40-
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.584 2009/07/08 18:55:35 tgl Exp $
40+
* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.585 2009/07/24 20:12:42 mha Exp $
4141
*
4242
* NOTES
4343
*
@@ -3635,14 +3635,33 @@ internal_forkexec(int argc, char *argv[], Port *port)
36353635
return-1;/* log made by save_backend_variables */
36363636
}
36373637

3638-
/* Drop the shared memory that is now inherited to the backend */
3638+
/* Drop theparametershared memory that is now inherited to the backend */
36393639
if (!UnmapViewOfFile(param))
36403640
elog(LOG,"could not unmap view of backend parameter file: error code %d",
36413641
(int)GetLastError());
36423642
if (!CloseHandle(paramHandle))
36433643
elog(LOG,"could not close handle to backend parameter file: error code %d",
36443644
(int)GetLastError());
36453645

3646+
/*
3647+
* Reserve the memory region used by our main shared memory segment before we
3648+
* resume the child process.
3649+
*/
3650+
if (!pgwin32_ReserveSharedMemoryRegion(pi.hProcess))
3651+
{
3652+
/*
3653+
* Failed to reserve the memory, so terminate the newly created
3654+
* process and give up.
3655+
*/
3656+
if (!TerminateProcess(pi.hProcess,255))
3657+
ereport(ERROR,
3658+
(errmsg_internal("could not terminate process that failed to reserve memory: error code %d",
3659+
(int)GetLastError())));
3660+
CloseHandle(pi.hProcess);
3661+
CloseHandle(pi.hThread);
3662+
return-1;/* logging done made by pgwin32_ReserveSharedMemoryRegion() */
3663+
}
3664+
36463665
/*
36473666
* Now that the backend variables are written out, we start the child
36483667
* thread so it can start initializing while we set up the rest of the

‎src/include/port/win32.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.88 2009/06/11 14:49:12 momjian Exp $ */
1+
/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.89 2009/07/24 20:12:42 mha Exp $ */
22

33
#if defined(_MSC_VER)|| defined(__BORLANDC__)
44
#defineWIN32_ONLY_COMPILER
@@ -288,6 +288,9 @@ extern intpgwin32_is_admin(void);
288288
externintpgwin32_is_service(void);
289289
#endif
290290

291+
/* in backend/port/win32_shmem.c */
292+
externintpgwin32_ReserveSharedMemoryRegion(HANDLE);
293+
291294
/* in port/win32error.c */
292295
externvoid_dosmaperr(unsigned long);
293296

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