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Fix memory leak on DSM slot exhaustion.

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If we attempt to create a DSM segment when no slots are available,
we should return the memory to the operating system.  Previously
we did that if the DSM_CREATE_NULL_IF_MAXSEGMENTS flag was
passed in, but we didn't do it if an error was raised.  Repair.

Back-patch to 9.4, where DSM segments arrived.

Author: Thomas Munro
Reviewed-by: Robert Haas
Reported-by: Julian Backes
Discussion: https://postgr.es/m/CA%2BhUKGKAAoEw-R4om0d2YM4eqT1eGEi6%3DQot-3ceDR-SLiWVDw%40mail.gmail.com
This commit is contained in:
Thomas Munro 2020-02-01 14:29:13 +13:00
parent 25dc267a1b
commit 600387f5dd
1 changed files with 8 additions and 9 deletions
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5
src/backend/storage/ipc/dsm.c
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@ -498,8 +498,6 @@ dsm_create(Size size, int flags)
/* Verify that we can support an additional mapping. */
if (nitems >= dsm_control->maxitems)
{
if ((flags & DSM_CREATE_NULL_IF_MAXSEGMENTS) != 0)
{
LWLockRelease(DynamicSharedMemoryControlLock);
dsm_impl_op(DSM_OP_DESTROY, seg->handle, 0, &seg->impl_private,
@ -508,8 +506,9 @@ dsm_create(Size size, int flags)
ResourceOwnerForgetDSM(seg->resowner, seg);
dlist_delete(&seg->node);
pfree(seg);
if ((flags & DSM_CREATE_NULL_IF_MAXSEGMENTS) != 0)
return NULL;
}
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
errmsg("too many dynamic shared memory segments")));