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Commit5d540ad

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Make the win32 shared memory code try 10 times instead of one if
it fails because the shared memory segment already exists. Thismeans it can take up to 10 seconds before it reports the errorif it *does* exist, but hopefully it will make the system capableof restarting even when the server is under high load.
1 parent9f4e9bf commit5d540ad

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1 file changed

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‎src/backend/port/win32_shmem.c‎

Lines changed: 34 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
77
*
88
* IDENTIFICATION
9-
* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.8 2009/05/04 08:36:40 mha Exp $
9+
* $PostgreSQL: pgsql/src/backend/port/win32_shmem.c,v 1.9 2009/05/05 09:48:51 mha Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -123,6 +123,7 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port)
123123
HANDLEhmap,
124124
hmap2;
125125
char*szShareMem;
126+
inti;
126127

127128
/* Room for a header? */
128129
Assert(size>MAXALIGN(sizeof(PGShmemHeader)));
@@ -131,54 +132,53 @@ PGSharedMemoryCreate(Size size, bool makePrivate, int port)
131132

132133
UsedShmemSegAddr=NULL;
133134

134-
/* In case CreateFileMapping() doesn't set the error code to 0 on success */
135-
SetLastError(0);
136-
137-
hmap=CreateFileMapping((HANDLE)0xFFFFFFFF,/* Use the pagefile */
138-
NULL,/* Default security attrs */
139-
PAGE_READWRITE,/* Memory is Read/Write */
140-
0L,/* Size Upper 32 Bits*/
141-
(DWORD)size,/* Size Lower 32 bits */
142-
szShareMem);
143-
144-
if (!hmap)
145-
ereport(FATAL,
146-
(errmsg("could not create shared memory segment: %lu",GetLastError()),
147-
errdetail("Failed system call was CreateFileMapping(size=%lu, name=%s).",
148-
(unsigned long)size,szShareMem)));
149-
150135
/*
151-
* If the segment already existed, CreateFileMapping() will return a
152-
* handle to the existing one.
136+
* When recycling a shared memory segment, it may take a short while
137+
* before it gets dropped from the global namespace. So re-try after
138+
* sleeping for a second, and continue retrying 10 times.
139+
* (both the 1 second time and the 10 retries are completely arbitrary)
153140
*/
154-
if (GetLastError()==ERROR_ALREADY_EXISTS)
141+
for (i=0;i<10;i++)
155142
{
156-
/*
157-
* When recycling a shared memory segment, it may take a short while
158-
* before it gets dropped from the global namespace. So re-try after
159-
* sleeping for a second.
160-
*/
161-
CloseHandle(hmap);/* Close the old handle, since we got a valid
162-
* one to the previous segment. */
163-
164-
Sleep(1000);
165-
166143
/* In case CreateFileMapping() doesn't set the error code to 0 on success */
167144
SetLastError(0);
168145

169-
hmap=CreateFileMapping((HANDLE)0xFFFFFFFF,NULL,PAGE_READWRITE,0L, (DWORD)size,szShareMem);
146+
hmap=CreateFileMapping((HANDLE)0xFFFFFFFF,/* Use the pagefile */
147+
NULL,/* Default security attrs */
148+
PAGE_READWRITE,/* Memory is Read/Write */
149+
0L,/* Size Upper 32 Bits*/
150+
(DWORD)size,/* Size Lower 32 bits */
151+
szShareMem);
152+
170153
if (!hmap)
171154
ereport(FATAL,
172155
(errmsg("could not create shared memory segment: %lu",GetLastError()),
173156
errdetail("Failed system call was CreateFileMapping(size=%lu, name=%s).",
174157
(unsigned long)size,szShareMem)));
175158

159+
/*
160+
* If the segment already existed, CreateFileMapping() will return a
161+
* handle to the existing one.
162+
*/
176163
if (GetLastError()==ERROR_ALREADY_EXISTS)
177-
ereport(FATAL,
178-
(errmsg("pre-existing shared memory block is still in use"),
179-
errhint("Check if there are any old server processes still running, and terminate them.")));
164+
{
165+
CloseHandle(hmap);/* Close the old handle, since we got a valid
166+
* one to the previous segment. */
167+
Sleep(1000);
168+
continue;
169+
}
170+
break;
180171
}
181172

173+
/*
174+
* If the last call in the loop still returned ERROR_ALREADY_EXISTS, this shared memory
175+
* segment exists and we assume it belongs to somebody else.
176+
*/
177+
if (GetLastError()==ERROR_ALREADY_EXISTS)
178+
ereport(FATAL,
179+
(errmsg("pre-existing shared memory block is still in use"),
180+
errhint("Check if there are any old server processes still running, and terminate them.")));
181+
182182
free(szShareMem);
183183

184184
/*

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