On Mon, Aug 10, 2009 at 19:33, Magnus Hagander<[email protected]> wrote:
> On Mon, Aug 10, 2009 at 16:58, Tom Lane<[email protected]> wrote:
>> Magnus Hagander <[email protected]> writes:
>>> On Mon, Aug 10, 2009 at 16:10, Tom Lane<[email protected]> wrote:
>>>> 8.2 as well, no?
>>
>>> 8.2 has a different shmem implementation - the one that emulates sysv
>>> shmem. The patch will need to be changed around for that, and I
>>> haven't looked at that. It may be worthwhile to do that, but it's a
>>> separate patch, so let's get it out in 8.3 and 8.4 first.
>>
>> If it's at all hard to do, I could see deprecating 8.2 for Windows
>> instead.
>
> I haven't looked at how much work it would be at all yet. So let's do
> that before we decide to deprecate anything. As mentioned downthread,
> 8.2 is a very widespread release, and we really want to avoid
> deprecating it.
Here's an attempt at a backport to 8.2. I haven't examined it in
detail, but it passes "make check" on mingw.
Comments?
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
*** a/src/backend/port/sysv_shmem.c
--- b/src/backend/port/sysv_shmem.c
***************
*** 49,54 **** typedef int IpcMemoryId; /* shared memory ID returned by shmget(2) */
--- 49,57 ----
unsigned long UsedShmemSegID = 0;
void *UsedShmemSegAddr = NULL;
+ #ifdef WIN32
+ Size UsedShmemSegSize = 0;
+ #endif
static void *InternalIpcMemoryCreate(IpcMemoryKey memKey, Size size);
static void IpcMemoryDetach(int status, Datum shmaddr);
***************
*** 403,408 **** PGSharedMemoryCreate(Size size, bool makePrivate, int port)
--- 406,412 ----
/* Save info for possible future use */
UsedShmemSegAddr = memAddress;
+ UsedShmemSegSize = size;
UsedShmemSegID = (unsigned long) NextShmemSegID;
return hdr;
*** a/src/backend/port/win32/shmem.c
--- b/src/backend/port/win32/shmem.c
***************
*** 12,19 ****
--- 12,22 ----
*/
#include "postgres.h"
+ #include "miscadmin.h"
static DWORD s_segsize = 0;
+ extern void *UsedShmemSegAddr;
+ extern Size UsedShmemSegSize;
/* Detach from a shared mem area based on its address */
int
***************
*** 29,34 **** shmdt(const void *shmaddr)
--- 32,44 ----
void *
shmat(int memId, void *shmaddr, int flag)
{
+ /* Release the memory region reserved in the postmaster */
+ if (IsUnderPostmaster)
+ {
+ if (VirtualFree(shmaddr, 0, MEM_RELEASE) == 0)
+ elog(FATAL, "failed to release reserved memory region (addr=%p): %lu",
+ shmaddr, GetLastError());
+ }
/* TODO -- shmat needs to count # attached to shared mem */
void *lpmem = MapViewOfFileEx((HANDLE) memId,
FILE_MAP_WRITE | FILE_MAP_READ,
***************
*** 128,130 **** shmget(int memKey, int size, int flag)
--- 138,190 ----
return (int) hmap;
}
+
+ /*
+ * 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;
+ }
*** a/src/backend/postmaster/postmaster.c
--- b/src/backend/postmaster/postmaster.c
***************
*** 3184,3190 **** 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 */
if (!UnmapViewOfFile(param))
elog(LOG, "could not unmap view of backend parameter file: error code %d",
(int) GetLastError());
--- 3184,3190 ----
return -1; /* log made by save_backend_variables */
}
! /* 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());
***************
*** 3193,3198 **** internal_forkexec(int argc, char *argv[], Port *port)
--- 3193,3217 ----
(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
* parent state.
*** a/src/include/port/win32.h
--- b/src/include/port/win32.h
***************
*** 263,268 **** extern int pgwin32_is_admin(void);
--- 263,271 ----
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);
--
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