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Fix double shared memory allocation.

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SLRU buffer lwlocks are allocated twice by oversight in commit
fe702a7b3f9f2bc5bf6d173166d7d55226af82c8 where that locks were moved to
separate tranche. The bug doesn't have user-visible effects except small
overspending of shared memory.

Backpatch to 9.6 where it was introduced.

Alexander Korotkov with small editorization by me.
This commit is contained in:
Teodor Sigaev 2017-07-21 13:31:20 +03:00
parent 68f785fd52
commit 7e1fb4c59e
1 changed files with 7 additions and 3 deletions
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10
src/backend/access/transam/slru.c
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@ -205,15 +205,16 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
shared->page_lru_count = (int *) (ptr + offset); shared->page_lru_count = (int *) (ptr + offset);
offset += MAXALIGN(nslots * sizeof(int)); offset += MAXALIGN(nslots * sizeof(int));
/* Initialize LWLocks */
shared->buffer_locks = (LWLockPadded *) (ptr + offset);
offset += MAXALIGN(nslots * sizeof(LWLockPadded));
if (nlsns > 0) if (nlsns > 0)
{ {
shared->group_lsn = (XLogRecPtr *) (ptr + offset); shared->group_lsn = (XLogRecPtr *) (ptr + offset);
offset += MAXALIGN(nslots * nlsns * sizeof(XLogRecPtr)); offset += MAXALIGN(nslots * nlsns * sizeof(XLogRecPtr));
} }
/* Initialize LWLocks */
shared->buffer_locks = (LWLockPadded *) ShmemAlloc(sizeof(LWLockPadded) * nslots);
Assert(strlen(name) + 1 < SLRU_MAX_NAME_LENGTH); Assert(strlen(name) + 1 < SLRU_MAX_NAME_LENGTH);
strlcpy(shared->lwlock_tranche_name, name, SLRU_MAX_NAME_LENGTH); strlcpy(shared->lwlock_tranche_name, name, SLRU_MAX_NAME_LENGTH);
shared->lwlock_tranche_id = tranche_id; shared->lwlock_tranche_id = tranche_id;
@ -230,6 +231,9 @@ SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,
shared->page_lru_count[slotno] = 0; shared->page_lru_count[slotno] = 0;
ptr += BLCKSZ; ptr += BLCKSZ;
} }
/* Should fit to estimated shmem size */
Assert(ptr - (char *) shared <= SimpleLruShmemSize(nslots, nlsns));
} }
else else
Assert(found); Assert(found);