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Commit72e78d8

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author
Amit Kapila
committed
Add assert to ensure that page locks don't participate in deadlock cycle.
Assert that we don't acquire any other heavyweight lock while holding thepage lock except for relation extension. However, these locks are nevertaken in reverse order which implies that page locks will neverparticipate in the deadlock cycle.Similar to relation extension, page locks are also held for a shortduration, so imposing such a restriction won't hurt.Author: Dilip Kumar, with few changes by Amit KapilaReviewed-by: Amit Kapila, Kuntal Ghosh and Sawada MasahikoDiscussion:https://postgr.es/m/CAD21AoCmT3cFQUN4aVvzy5chw7DuzXrJCbrjTU05B+Ss=Gn1LA@mail.gmail.com
1 parent6312c08 commit72e78d8

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  • src/backend/storage/lmgr

1 file changed

+24
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‎src/backend/storage/lmgr/lock.c

Lines changed: 24 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -185,6 +185,18 @@ static intFastPathLocalUseCount = 0;
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*/
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staticboolIsRelationExtensionLockHeldPG_USED_FOR_ASSERTS_ONLY= false;
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/*
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* Flag to indicate if the page lock is held by this backend. We don't
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* acquire any other heavyweight lock while holding the page lock except for
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* relation extension. However, these locks are never taken in reverse order
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* which implies that page locks will also never participate in the deadlock
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* cycle.
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*
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* Similar to relation extension, page locks are also held for a short
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* duration, so imposing such a restriction won't hurt.
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*/
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staticboolIsPageLockHeldPG_USED_FOR_ASSERTS_ONLY= false;
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/* Macros for manipulating proc->fpLockBits */
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#defineFAST_PATH_BITS_PER_SLOT3
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#defineFAST_PATH_LOCKNUMBER_OFFSET1
@@ -862,6 +874,13 @@ LockAcquireExtended(const LOCKTAG *locktag,
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*/
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Assert(!IsRelationExtensionLockHeld);
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/*
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* We don't acquire any other heavyweight lock while holding the page lock
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* except for relation extension.
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*/
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Assert(!IsPageLockHeld||
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(locktag->locktag_type==LOCKTAG_RELATION_EXTEND));
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/*
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* Prepare to emit a WAL record if acquisition of this lock needs to be
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* replayed in a standby server.
@@ -1310,10 +1329,10 @@ SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc,
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}
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/*
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* Check and set/reset the flag that we hold the relation extension lock.
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* Check and set/reset the flag that we hold the relation extension/page lock.
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*
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* It is callers responsibility that this function is called after
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* acquiring/releasing the relation extension lock.
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* acquiring/releasing the relation extension/page lock.
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*
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* Pass acquired as true if lock is acquired, false otherwise.
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*/
@@ -1323,6 +1342,9 @@ CheckAndSetLockHeld(LOCALLOCK *locallock, bool acquired)
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#ifdefUSE_ASSERT_CHECKING
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if (LOCALLOCK_LOCKTAG(*locallock)==LOCKTAG_RELATION_EXTEND)
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IsRelationExtensionLockHeld=acquired;
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elseif (LOCALLOCK_LOCKTAG(*locallock)==LOCKTAG_PAGE)
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IsPageLockHeld=acquired;
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#endif
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}
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