Reserve the shared memory region during backend startup on Windows, so
that memory allocated by starting third party DLLs doesn't end up conflicting with it. Hopefully this solves the long-time issue with "could not reattach to shared memory" errors on Win32. Patch from Tsutomu Yamada and me, based on idea from Trevor Talbot.
This commit is contained in:
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5e22994127
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a7e587863c
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@ -6,7 +6,7 @@
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* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.11 2009/06/11 14:49:00 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.12 2009/07/24 20:12:42 mha Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -18,6 +18,7 @@
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unsigned long UsedShmemSegID = 0;
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void *UsedShmemSegAddr = NULL;
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static Size UsedShmemSegSize = 0;
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static void pgwin32_SharedMemoryDelete(int status, Datum shmId);
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@ -233,6 +234,7 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port)
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/* Save info for possible future use */
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UsedShmemSegAddr = memAddress;
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UsedShmemSegSize = size;
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UsedShmemSegID = (unsigned long) hmap2;
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return hdr;
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@ -257,6 +259,13 @@ PGSharedMemoryReAttach(void)
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Assert(UsedShmemSegAddr != NULL);
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Assert(IsUnderPostmaster);
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/*
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* Release memory region reservation that was made by the postmaster
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*/
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if (VirtualFree(UsedShmemSegAddr, 0, MEM_RELEASE) == 0)
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elog(FATAL, "failed to release reserved memory region (addr=%p): %lu",
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UsedShmemSegAddr, GetLastError());
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hdr = (PGShmemHeader *) MapViewOfFileEx((HANDLE) UsedShmemSegID, FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, 0, UsedShmemSegAddr);
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if (!hdr)
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elog(FATAL, "could not reattach to shared memory (key=%d, addr=%p): %lu",
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@ -302,3 +311,53 @@ pgwin32_SharedMemoryDelete(int status, Datum shmId)
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if (!CloseHandle((HANDLE) DatumGetInt32(shmId)))
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elog(LOG, "could not close handle to shared memory: %lu", GetLastError());
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}
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/*
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* pgwin32_ReserveSharedMemoryRegion(hChild)
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*
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* Reserve the memory region that will be used for shared memory in a child
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* process. It is called before the child process starts, to make sure the
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* memory is available.
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*
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* Once the child starts, DLLs loading in different order or threads getting
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* scheduled differently may allocate memory which can conflict with the
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* address space we need for our shared memory. By reserving the shared
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* memory region before the child starts, and freeing it only just before we
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* attempt to get access to the shared memory forces these allocations to
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* be given different address ranges that don't conflict.
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*
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* NOTE! This function executes in the postmaster, and should for this
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* reason not use elog(FATAL) since that would take down the postmaster.
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*/
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int
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pgwin32_ReserveSharedMemoryRegion(HANDLE hChild)
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{
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void *address;
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Assert(UsedShmemSegAddr != NULL);
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Assert(UsedShmemSegSize != 0);
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address = VirtualAllocEx(hChild, UsedShmemSegAddr, UsedShmemSegSize,
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MEM_RESERVE, PAGE_READWRITE);
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if (address == NULL) {
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/* Don't use FATAL since we're running in the postmaster */
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elog(LOG, "could not reserve shared memory region (addr=%p) for child %lu: %lu",
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UsedShmemSegAddr, hChild, GetLastError());
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return false;
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}
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if (address != UsedShmemSegAddr)
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{
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/*
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* Should never happen - in theory if allocation granularity causes strange
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* effects it could, so check just in case.
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*
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* Don't use FATAL since we're running in the postmaster.
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*/
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elog(LOG, "reserved shared memory region got incorrect address %p, expected %p",
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address, UsedShmemSegAddr);
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VirtualFreeEx(hChild, address, 0, MEM_RELEASE);
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return false;
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}
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return true;
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}
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@ -37,7 +37,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.584 2009/07/08 18:55:35 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.585 2009/07/24 20:12:42 mha Exp $
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*
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* NOTES
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*
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@ -3635,7 +3635,7 @@ internal_forkexec(int argc, char *argv[], Port *port)
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return -1; /* log made by save_backend_variables */
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}
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/* Drop the shared memory that is now inherited to the backend */
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/* Drop the parameter shared memory that is now inherited to the backend */
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if (!UnmapViewOfFile(param))
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elog(LOG, "could not unmap view of backend parameter file: error code %d",
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(int) GetLastError());
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elog(LOG, "could not close handle to backend parameter file: error code %d",
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(int) GetLastError());
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/*
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* Reserve the memory region used by our main shared memory segment before we
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* resume the child process.
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*/
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if (!pgwin32_ReserveSharedMemoryRegion(pi.hProcess))
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{
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/*
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* Failed to reserve the memory, so terminate the newly created
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* process and give up.
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*/
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if (!TerminateProcess(pi.hProcess, 255))
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ereport(ERROR,
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(errmsg_internal("could not terminate process that failed to reserve memory: error code %d",
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(int) GetLastError())));
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CloseHandle(pi.hProcess);
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CloseHandle(pi.hThread);
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return -1; /* logging done made by pgwin32_ReserveSharedMemoryRegion() */
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}
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/*
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* Now that the backend variables are written out, we start the child
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* thread so it can start initializing while we set up the rest of the
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@ -1,4 +1,4 @@
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/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.88 2009/06/11 14:49:12 momjian Exp $ */
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/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.89 2009/07/24 20:12:42 mha Exp $ */
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#if defined(_MSC_VER) || defined(__BORLANDC__)
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#define WIN32_ONLY_COMPILER
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@ -288,6 +288,9 @@ extern int pgwin32_is_admin(void);
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extern int pgwin32_is_service(void);
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#endif
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/* in backend/port/win32_shmem.c */
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extern int pgwin32_ReserveSharedMemoryRegion(HANDLE);
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/* in port/win32error.c */
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extern void _dosmaperr(unsigned long);
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