From a7e587863cab80b8896593f20b41e53d65155932 Mon Sep 17 00:00:00 2001 From: Magnus Hagander Date: Fri, 24 Jul 2009 20:12:42 +0000 Subject: [PATCH] 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. --- src/backend/port/win32_shmem.c | 61 ++++++++++++++++++++++++++++- src/backend/postmaster/postmaster.c | 23 ++++++++++- src/include/port/win32.h | 5 ++- 3 files changed, 85 insertions(+), 4 deletions(-) diff --git a/src/backend/port/win32_shmem.c b/src/backend/port/win32_shmem.c index 4e819d0c65..9a17b86a9b 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 ed26a3f25e..58cb5cb989 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 9ace851ebb..4c0cc10463 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);