diff options
Diffstat (limited to 'src/backend/storage/lmgr/lock.c')
| -rw-r--r-- | src/backend/storage/lmgr/lock.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c index 1df7b8e2ab7..9f55132724f 100644 --- a/src/backend/storage/lmgr/lock.c +++ b/src/backend/storage/lmgr/lock.c @@ -170,6 +170,21 @@ typedef struct TwoPhaseLockRecord */ static int FastPathLocalUseCount = 0; +/* + * Flag to indicate if the relation extension lock is held by this backend. + * This flag is used to ensure that while holding the relation extension lock + * we don't try to acquire a heavyweight lock on any other object. This + * restriction implies that the relation extension lock won't ever participate + * in the deadlock cycle because we can never wait for any other heavyweight + * lock after acquiring this lock. + * + * Such a restriction is okay for relation extension locks as unlike other + * heavyweight locks these are not held till the transaction end. These are + * taken for a short duration to extend a particular relation and then + * released. + */ +static bool IsRelationExtensionLockHeld PG_USED_FOR_ASSERTS_ONLY = false; + /* Macros for manipulating proc->fpLockBits */ #define FAST_PATH_BITS_PER_SLOT 3 #define FAST_PATH_LOCKNUMBER_OFFSET 1 @@ -841,6 +856,13 @@ LockAcquireExtended(const LOCKTAG *locktag, } /* + * We don't acquire any other heavyweight lock while holding the relation + * extension lock. We do allow to acquire the same relation extension + * lock more than once but that case won't reach here. + */ + Assert(!IsRelationExtensionLockHeld); + + /* * Prepare to emit a WAL record if acquisition of this lock needs to be * replayed in a standby server. * @@ -1288,6 +1310,23 @@ SetupLockInTable(LockMethod lockMethodTable, PGPROC *proc, } /* + * Check and set/reset the flag that we hold the relation extension lock. + * + * It is callers responsibility that this function is called after + * acquiring/releasing the relation extension lock. + * + * Pass acquired as true if lock is acquired, false otherwise. + */ +static inline void +CheckAndSetLockHeld(LOCALLOCK *locallock, bool acquired) +{ +#ifdef USE_ASSERT_CHECKING + if (LOCALLOCK_LOCKTAG(*locallock) == LOCKTAG_RELATION_EXTEND) + IsRelationExtensionLockHeld = acquired; +#endif +} + +/* * Subroutine to free a locallock entry */ static void @@ -1322,6 +1361,11 @@ RemoveLocalLock(LOCALLOCK *locallock) (void *) &(locallock->tag), HASH_REMOVE, NULL)) elog(WARNING, "locallock table corrupted"); + + /* + * Indicate that the lock is released for certain types of locks + */ + CheckAndSetLockHeld(locallock, false); } /* @@ -1618,6 +1662,9 @@ GrantLockLocal(LOCALLOCK *locallock, ResourceOwner owner) locallock->numLockOwners++; if (owner != NULL) ResourceOwnerRememberLock(owner, locallock); + + /* Indicate that the lock is acquired for certain types of locks. */ + CheckAndSetLockHeld(locallock, true); } /* |