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Allow dynamic shared memory segments to be kept until shutdown.

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Amit Kapila, reviewed by Kyotaro Horiguchi, with some further
changes by me.
This commit is contained in:
Robert Haas
2014-03-10 14:04:47 -04:00
parent 5a991ef869
commit 8722017bbc
4 changed files with 75 additions and 1 deletions
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45
src/backend/storage/ipc/dsm_impl.c
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@ -67,6 +67,7 @@
#include "storage/fd.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "postmaster/postmaster.h"
#ifdef USE_DSM_POSIX
static bool dsm_impl_posix(dsm_op op, dsm_handle handle, Size request_size,
@ -113,6 +114,8 @@ int dynamic_shared_memory_type;
/* Size of buffer to be used for zero-filling. */
#define ZBUFFER_SIZE 8192
#define SEGMENT_NAME_PREFIX "Global/PostgreSQL"
/*------
* Perform a low-level shared memory operation in a platform-specific way,
* as dictated by the selected implementation. Each implementation is
@ -635,7 +638,7 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size,
* convention similar to main shared memory. We can change here once
* issue mentioned in GetSharedMemName is resolved.
*/
snprintf(name, 64, "Global/PostgreSQL.%u", handle);
snprintf(name, 64, "%s.%u", SEGMENT_NAME_PREFIX, handle);
/*
* Handle teardown cases. Since Windows automatically destroys the object
@ -982,6 +985,46 @@ dsm_impl_mmap(dsm_op op, dsm_handle handle, Size request_size,
}
#endif
/*
* Implementation-specific actions that must be performed when a segment
* is to be preserved until postmaster shutdown.
*
* Except on Windows, we don't need to do anything at all. But since Windows
* cleans up segments automatically when no references remain, we duplicate
* the segment handle into the postmaster process. The postmaster needn't
* do anything to receive the handle; Windows transfers it automatically.
*/
void
dsm_impl_keep_segment(dsm_handle handle, void *impl_private)
{
switch (dynamic_shared_memory_type)
{
#ifdef USE_DSM_WINDOWS
case DSM_IMPL_WINDOWS:
{
HANDLE hmap;
if (!DuplicateHandle(GetCurrentProcess(), impl_private,
PostmasterHandle, &hmap, 0, FALSE,
DUPLICATE_SAME_ACCESS))
{
char name[64];
snprintf(name, 64, "%s.%u", SEGMENT_NAME_PREFIX, handle);
_dosmaperr(GetLastError());
ereport(ERROR,
(errcode_for_dynamic_shared_memory(),
errmsg("could not duplicate handle for \"%s\": %m",
name)));
}
break;
}
#endif
default:
break;
}
}
static int
errcode_for_dynamic_shared_memory()
{