diff --git a/src/backend/port/win32_shmem.c b/src/backend/port/win32_shmem.c
index 4e819d0c65bc53c37dd863db75f0a53546c44469..9a17b86a9b1267941f8e4502baf3c501288b88d0 100644
--- a/src/backend/port/win32_shmem.c
+++ b/src/backend/port/win32_shmem.c
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.11 2009/06/11 14:49:00 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.12 2009/07/24 20:12:42 mha Exp $
*
*-------------------------------------------------------------------------
*/
@@ -18,6 +18,7 @@
unsigned long UsedShmemSegID = 0;
void *UsedShmemSegAddr = NULL;
+static Size UsedShmemSegSize = 0;
static void pgwin32_SharedMemoryDelete(int status, Datum shmId);
@@ -233,6 +234,7 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port)
/* Save info for possible future use */
UsedShmemSegAddr = memAddress;
+ UsedShmemSegSize = size;
UsedShmemSegID = (unsigned long) hmap2;
return hdr;
@@ -257,6 +259,13 @@ PGSharedMemoryReAttach(void)
Assert(UsedShmemSegAddr != NULL);
Assert(IsUnderPostmaster);
+ /*
+ * Release memory region reservation that was made by the postmaster
+ */
+ if (VirtualFree(UsedShmemSegAddr, 0, MEM_RELEASE) == 0)
+ elog(FATAL, "failed to release reserved memory region (addr=%p): %lu",
+ UsedShmemSegAddr, GetLastError());
+
hdr = (PGShmemHeader *) MapViewOfFileEx((HANDLE) UsedShmemSegID, FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, 0, UsedShmemSegAddr);
if (!hdr)
elog(FATAL, "could not reattach to shared memory (key=%d, addr=%p): %lu",
@@ -302,3 +311,53 @@ pgwin32_SharedMemoryDelete(int status, Datum shmId)
if (!CloseHandle((HANDLE) DatumGetInt32(shmId)))
elog(LOG, "could not close handle to shared memory: %lu", GetLastError());
}
+
+/*
+ * pgwin32_ReserveSharedMemoryRegion(hChild)
+ *
+ * Reserve the memory region that will be used for shared memory in a child
+ * process. It is called before the child process starts, to make sure the
+ * memory is available.
+ *
+ * Once the child starts, DLLs loading in different order or threads getting
+ * scheduled differently may allocate memory which can conflict with the
+ * address space we need for our shared memory. By reserving the shared
+ * memory region before the child starts, and freeing it only just before we
+ * attempt to get access to the shared memory forces these allocations to
+ * be given different address ranges that don't conflict.
+ *
+ * NOTE! This function executes in the postmaster, and should for this
+ * reason not use elog(FATAL) since that would take down the postmaster.
+ */
+int
+pgwin32_ReserveSharedMemoryRegion(HANDLE hChild)
+{
+ void *address;
+
+ Assert(UsedShmemSegAddr != NULL);
+ Assert(UsedShmemSegSize != 0);
+
+ address = VirtualAllocEx(hChild, UsedShmemSegAddr, UsedShmemSegSize,
+ MEM_RESERVE, PAGE_READWRITE);
+ if (address == NULL) {
+ /* Don't use FATAL since we're running in the postmaster */
+ elog(LOG, "could not reserve shared memory region (addr=%p) for child %lu: %lu",
+ UsedShmemSegAddr, hChild, GetLastError());
+ return false;
+ }
+ if (address != UsedShmemSegAddr)
+ {
+ /*
+ * Should never happen - in theory if allocation granularity causes strange
+ * effects it could, so check just in case.
+ *
+ * Don't use FATAL since we're running in the postmaster.
+ */
+ elog(LOG, "reserved shared memory region got incorrect address %p, expected %p",
+ address, UsedShmemSegAddr);
+ VirtualFreeEx(hChild, address, 0, MEM_RELEASE);
+ return false;
+ }
+
+ return true;
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index ed26a3f25ec9bece7056a7724b0d84ed03007cde..58cb5cb989f71b17c1151e7a901282505bfd95eb 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.584 2009/07/08 18:55:35 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.585 2009/07/24 20:12:42 mha Exp $
*
* NOTES
*
@@ -3635,7 +3635,7 @@ internal_forkexec(int argc, char *argv[], Port *port)
return -1; /* log made by save_backend_variables */
}
- /* Drop the shared memory that is now inherited to the backend */
+ /* Drop the parameter shared memory that is now inherited to the backend */
if (!UnmapViewOfFile(param))
elog(LOG, "could not unmap view of backend parameter file: error code %d",
(int) GetLastError());
@@ -3643,6 +3643,25 @@ internal_forkexec(int argc, char *argv[], Port *port)
elog(LOG, "could not close handle to backend parameter file: error code %d",
(int) GetLastError());
+ /*
+ * Reserve the memory region used by our main shared memory segment before we
+ * resume the child process.
+ */
+ if (!pgwin32_ReserveSharedMemoryRegion(pi.hProcess))
+ {
+ /*
+ * Failed to reserve the memory, so terminate the newly created
+ * process and give up.
+ */
+ if (!TerminateProcess(pi.hProcess, 255))
+ ereport(ERROR,
+ (errmsg_internal("could not terminate process that failed to reserve memory: error code %d",
+ (int) GetLastError())));
+ CloseHandle(pi.hProcess);
+ CloseHandle(pi.hThread);
+ return -1; /* logging done made by pgwin32_ReserveSharedMemoryRegion() */
+ }
+
/*
* Now that the backend variables are written out, we start the child
* thread so it can start initializing while we set up the rest of the
diff --git a/src/include/port/win32.h b/src/include/port/win32.h
index 9ace851ebba44a7f66d05d1104bd49825203f492..4c0cc104632069c3930624f988b7d1953d6ea4d1 100644
--- a/src/include/port/win32.h
+++ b/src/include/port/win32.h
@@ -1,4 +1,4 @@
-/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.88 2009/06/11 14:49:12 momjian Exp $ */
+/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.89 2009/07/24 20:12:42 mha Exp $ */
#if defined(_MSC_VER) || defined(__BORLANDC__)
#define WIN32_ONLY_COMPILER
@@ -288,6 +288,9 @@ extern int pgwin32_is_admin(void);
extern int pgwin32_is_service(void);
#endif
+/* in backend/port/win32_shmem.c */
+extern int pgwin32_ReserveSharedMemoryRegion(HANDLE);
+
/* in port/win32error.c */
extern void _dosmaperr(unsigned long);